Spring 学习记录6 BeanFactory(2)

主题

除了Spring 学习记录5 BeanFactory 里写的几个接口外,BeanFactory的实现类还实现了一些其他接口,这篇文章主要介绍这些接口和实现类.

结构

DefaultListableBeanFactory和它的父类们除了实现了BF的各种接口以外还实现了AliasRegistry和BeanDefinitionRegistry接口.而且不同等级的父类和BF的相关接口都有交集..

AliasRegistry

这个接口根据说明来看意思是提供别名注册的服务.虽然没有实际使用过别名,不过1个bean确实可以有N个别名.

/*
 * Copyright 2002-2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core;

/**
 * Common interface for managing aliases. Serves as super-interface for
 * {@link org.springframework.beans.factory.support.BeanDefinitionRegistry}.
 *
 * @author Juergen Hoeller
 * @since 2.5.2
 */
public interface AliasRegistry {

    /**
     * Given a name, register an alias for it.
     * @param name the canonical name
     * @param alias the alias to be registered
     * @throws IllegalStateException if the alias is already in use
     * and may not be overridden
     */
    void registerAlias(String name, String alias);

    /**
     * Remove the specified alias from this registry.
     * @param alias the alias to remove
     * @throws IllegalStateException if no such alias was found
     */
    void removeAlias(String alias);

    /**
     * Determine whether this given name is defines as an alias
     * (as opposed to the name of an actually registered component).
     * @param beanName the bean name to check
     * @return whether the given name is an alias
     */
    boolean isAlias(String beanName);

    /**
     * Return the aliases for the given name, if defined.
     * @param name the name to check for aliases
     * @return the aliases, or an empty array if none
     */
    String[] getAliases(String name);

}

接口就4个方法.

1.为1个beanname注册1个别名,

2.删除1个别名

3.判断1个name是否是别名

4.根据beanname获取所有别名.

SimpleAliasRegistry

这个类实现了AliasRegistry,用了1个ConcurrentHashMap来存储所有别名的映射关系.

测试代码:

package spring.bf;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.core.SimpleAliasRegistry;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.util.StringValueResolver;

import java.util.Arrays;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:test-application-context.xml")
public class SimpleAliasRegistryTest {

    SimpleAliasRegistry simpleAliasRegistry = new SimpleAliasRegistry();

    /**
     * 别名不能循环引用
     * 会调用checkForAliasCircle方法,做循环引用的检查
     * 里面会调用canonicalName方法,这个方法会不停的用传入的name当做别名去找他对应的beanname,层层找下去,找到最后1个beanname以后和alias比较一下,如果一直,说明有循环引用就抛出异常
     */
    @Test
    public void test() {
        simpleAliasRegistry.registerAlias("b1", "a1");
        simpleAliasRegistry.registerAlias("a1", "a2");
        //simpleAliasRegistry.registerAlias("a2", "b1"); //java.lang.IllegalStateException: Cannot register alias 'b1' for name 'a2': Circular reference - 'a2' is a direct or indirect alias for 'b1' already
    }

    /**
     * 默认情况下别名可以覆盖
     * 根据子类会不会重写allowAliasOverriding来做决定,默认是true
     */
    @Test
    public void test2() {
        simpleAliasRegistry.registerAlias("b1", "a1");
        simpleAliasRegistry.registerAlias("b2", "a1");
        System.out.println(Arrays.toString(simpleAliasRegistry.getAliases("b1"))); // []
        System.out.println(Arrays.toString(simpleAliasRegistry.getAliases("b2"))); // [a1]
    }

    /**
     * 移除不存在的bean会抛异常
     * 所以调用之前可以先用isAlias做判断
     */
    @Test
    public void test3() {
        //simpleAliasRegistry.removeAlias("not exists"); // java.lang.IllegalStateException: No alias 'not exists' registered
    }

    // getAliases会调用retrieveAliases方法,它会递归调用自身,根据beanname找到alias,再把alias当做beanname,把所有的alias都找出来.

    /**
     * 测试resolveAliases方法
     */
    @Test
    public void test4() {
        simpleAliasRegistry.registerAlias("b1", "a1");
        simpleAliasRegistry.registerAlias("b2", "a2");
        // 报错
        // java.lang.IllegalStateException: Cannot register resolved alias 'a1' (original: 'a2') for name 'b2': It is already registered for name 'b2'.
        // 提示感觉有问题.其实应该提示It is already registered for name 'b1'.
        // 因为alias a2 被解析为a1, 而a1已经指向的是beanname b1,所以不能再指向b2
        simpleAliasRegistry.resolveAliases(new StringValueResolver() {
            @Override
            public String resolveStringValue(String strVal) {
                if (strVal.equals("a2")) {
                    return "a1";
                }
                return strVal;
            }
        });
    }
}

方法基本在测试里都测了.

另外感觉resolveAliases有一个提示有点问题,请参test4方法.

DefaultSingletonBeanRegistry

直接上注释吧...很多方法目前还不知道为什么这么写.什么时候会用到.看到后面的子类可能就会懂了.

/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory.support;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.*;
import org.springframework.beans.factory.config.SingletonBeanRegistry;
import org.springframework.core.SimpleAliasRegistry;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Generic registry for shared bean instances, implementing the
 * {@link org.springframework.beans.factory.config.SingletonBeanRegistry}.
 * Allows for registering singleton instances that should be shared
 * for all callers of the registry, to be obtained via bean name.
 * <p>
 * <p>Also supports registration of
 * {@link org.springframework.beans.factory.DisposableBean} instances,
 * (which might or might not correspond to registered singletons),
 * to be destroyed on shutdown of the registry. Dependencies between
 * beans can be registered to enforce an appropriate shutdown order.
 * <p>
 * <p>This class mainly serves as base class for
 * {@link org.springframework.beans.factory.BeanFactory} implementations,
 * factoring out the common management of singleton bean instances. Note that
 * the {@link org.springframework.beans.factory.config.ConfigurableBeanFactory}
 * interface extends the {@link SingletonBeanRegistry} interface.
 * <p>
 * <p>Note that this class assumes neither a bean definition concept
 * nor a specific creation process for bean instances, in contrast to
 * {@link AbstractBeanFactory} and {@link DefaultListableBeanFactory}
 * (which inherit from it). Can alternatively also be used as a nested
 * helper to delegate to.
 *
 * @author Juergen Hoeller
 * @see #registerSingleton
 * @see #registerDisposableBean
 * @see org.springframework.beans.factory.DisposableBean
 * @see org.springframework.beans.factory.config.ConfigurableBeanFactory
 * @since 2.0
 */
public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {

    /**
     * Internal marker for a null singleton object:
     * used as marker value for concurrent Maps (which don't support null values).
     * concurrent Maps里不能put null,所以用这个代替
     */
    protected static final Object NULL_OBJECT = new Object();


    /**
     * Logger available to subclasses
     */
    protected final Log logger = LogFactory.getLog(getClass());

    /**
     * Cache of singleton objects: bean name --> bean instance
     * 存单例的bean,FactoryBean也算
     */
    private final Map<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>(64);

    /**
     * Cache of singleton factories: bean name --> ObjectFactory
     * 存ObjectFactory,我自己没用过.
     * 测试的时候发现有循环引用的时候.比如A,B相互引用的时候,先扫描到A注册A.当前工厂的一个内部类对象会被注册到这里.有1个bean的引用指向B
     */
    private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<String, ObjectFactory<?>>(16);

    /**
     * Cache of early singleton objects: bean name --> bean instance
     * 一般情况下可能这个map都是空的,只有2个bean相互引用的时候才会有值.
     * 看英文解释似乎是一个bean还没被完全创建完的时候会被丢到这个map里.可能作用是先让其他bean先能够引用这个bean吧
     * 测试A和B相互引用,先扫描到A的话A会放到这里里面,然后开始注册B,B注册完了再remove
     */
    private final Map<String, Object> earlySingletonObjects = new HashMap<String, Object>(16);

    /**
     * Set of registered singletons, containing the bean names in registration order
     * 注册的bean的name都会放到这里
     */
    private final Set<String> registeredSingletons = new LinkedHashSet<String>(64);

    /**
     * Names of beans that are currently in creation
     * 注册A的时候如果A和B相互引用,A会被放到这里里面.和earlySingletonObjects一起使用
     */
    private final Set<String> singletonsCurrentlyInCreation =
            Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean>(16));

    /**
     * Names of beans currently excluded from in creation checks
     * 创建bean过程中有一些bean已经在创建了在创建会报错,用这个可以排除掉这个检查,不知道啥时候会用到
     */
    private final Set<String> inCreationCheckExclusions =
            Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean>(16));

    /**
     * List of suppressed Exceptions, available for associating related causes
     * 创建bean过程中出现一些特定的错误的时候可以无视这些错误继续创建
     */
    private Set<Exception> suppressedExceptions;

    /**
     * Flag that indicates whether we're currently within destroySingletons
     * 是否正在销毁bean,可能是factory在destroy的时候就不能再创建bean了
     */
    private boolean singletonsCurrentlyInDestruction = false;

    /**
     * Disposable bean instances: bean name --> disposable instance
     * 存disposableBean
     */
    private final Map<String, Object> disposableBeans = new LinkedHashMap<String, Object>();

    /**
     * Map between containing bean names: bean name --> Set of bean names that the bean contains
     * 似乎是用在innerbean和outerbean的时候使用.我一直没使用过这种bean
     */
    private final Map<String, Set<String>> containedBeanMap = new ConcurrentHashMap<String, Set<String>>(16);

    /**
     * Map between dependent bean names: bean name --> Set of dependent bean names
     * A中有B,那key就是B,value就是A.销毁B之前需要先销毁A
     */
    private final Map<String, Set<String>> dependentBeanMap = new ConcurrentHashMap<String, Set<String>>(64);

    /**
     * Map between depending bean names: bean name --> Set of bean names for the bean's dependencies
     * 和dependentBeanMap刚好相反,A中有B和C的引用.那key是A value是B和C
     */
    private final Map<String, Set<String>> dependenciesForBeanMap = new ConcurrentHashMap<String, Set<String>>(64);


    /**
     * 注册单例bean
     *
     * @param beanName
     * @param singletonObject
     * @throws IllegalStateException
     */
    @Override
    public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
        Assert.notNull(beanName, "'beanName' must not be null");
        synchronized (this.singletonObjects) {
            Object oldObject = this.singletonObjects.get(beanName);
            // 从singletonObjects获取bean,有bean说明已经注册过了不让重新注册
            if (oldObject != null) {
                throw new IllegalStateException("Could not register object [" + singletonObject +
                        "] under bean name '" + beanName + "': there is already object [" + oldObject + "] bound");
            }
            // 没注册过就掉注册方法
            addSingleton(beanName, singletonObject);
        }
    }

    /**
     * Add the given singleton object to the singleton cache of this factory.
     * <p>To be called for eager registration of singletons.
     * 注册1个单例bean
     *
     * @param beanName        the name of the bean
     * @param singletonObject the singleton object
     */
    protected void addSingleton(String beanName, Object singletonObject) {
        synchronized (this.singletonObjects) {
            // 注册的单例bean放到singletonObjects和registeredSingletons里,null的话为了防止map抛出异常所以要put一个默认的obj
            // 但是我也不知道为什么时候add的时候singletonFactories和earlySingletonObjects会有值,需要remove.
            this.singletonObjects.put(beanName, (singletonObject != null ? singletonObject : NULL_OBJECT));
            this.singletonFactories.remove(beanName);
            this.earlySingletonObjects.remove(beanName);
            this.registeredSingletons.add(beanName);
        }
    }

    /**
     * Add the given singleton factory for building the specified singleton
     * if necessary.
     * <p>To be called for eager registration of singletons, e.g. to be able to
     * resolve circular references.
     * 和addSingleton几乎一样的道理
     *
     * @param beanName         the name of the bean
     * @param singletonFactory the factory for the singleton object
     */
    protected void addSingletonFactory(String beanName, ObjectFactory<?> singletonFactory) {
        Assert.notNull(singletonFactory, "Singleton factory must not be null");
        synchronized (this.singletonObjects) {
            if (!this.singletonObjects.containsKey(beanName)) {
                this.singletonFactories.put(beanName, singletonFactory);
                this.earlySingletonObjects.remove(beanName);
                this.registeredSingletons.add(beanName);
            }
        }
    }

    @Override
    public Object getSingleton(String beanName) {
        return getSingleton(beanName, true);
    }

    /**
     * Return the (raw) singleton object registered under the given name.
     * <p>Checks already instantiated singletons and also allows for an early
     * reference to a currently created singleton (resolving a circular reference).
     * 获取一个单例
     *
     * @param beanName            the name of the bean to look for
     * @param allowEarlyReference whether early references should be created or not
     * @return the registered singleton object, or {@code null} if none found
     */
    protected Object getSingleton(String beanName, boolean allowEarlyReference) {
        Object singletonObject = this.singletonObjects.get(beanName);
        // 从singletonObjects中先获取,如果非空就直接返回,如果是空的,判断是否正在创建中
        if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
            synchronized (this.singletonObjects) {
                // 如果正在创建就从earlySingletonObjects中获取A,B相互引用先加载A的时候A会被先放到earlySingletonObjects中而不是singletonObjects中,因为A还没创建就需要创建B
                singletonObject = this.earlySingletonObjects.get(beanName);
                // 目前我还没遇到过allowEarlyReference为true的情况
                if (singletonObject == null && allowEarlyReference) {
                    ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
                    if (singletonFactory != null) {
                        singletonObject = singletonFactory.getObject();
                        this.earlySingletonObjects.put(beanName, singletonObject);
                        this.singletonFactories.remove(beanName);
                    }
                }
            }
        }
        return (singletonObject != NULL_OBJECT ? singletonObject : null);
    }

    /**
     * Return the (raw) singleton object registered under the given name,
     * creating and registering a new one if none registered yet.
     * 也是获取bean,但是没有的时候可以从工厂里获取
     *
     * @param beanName         the name of the bean
     * @param singletonFactory the ObjectFactory to lazily create the singleton
     *                         with, if necessary
     * @return the registered singleton object
     */
    public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
        Assert.notNull(beanName, "'beanName' must not be null");
        synchronized (this.singletonObjects) {
            // 获取bean
            Object singletonObject = this.singletonObjects.get(beanName);
            if (singletonObject == null) {
                // 如果工厂正在destroy.就直接抛异常
                if (this.singletonsCurrentlyInDestruction) {
                    throw new BeanCreationNotAllowedException(beanName,
                            "Singleton bean creation not allowed while the singletons of this factory are in destruction " +
                                    "(Do not request a bean from a BeanFactory in a destroy method implementation!)");
                }
                if (logger.isDebugEnabled()) {
                    logger.debug("Creating shared instance of singleton bean '" + beanName + "'");
                }
                // 创建之前做校验,如果已经正在创建了.就报错.
                beforeSingletonCreation(beanName);
                boolean newSingleton = false;
                boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
                if (recordSuppressedExceptions) {
                    this.suppressedExceptions = new LinkedHashSet<Exception>();
                }
                try {
                    // 从工厂里获取
                    singletonObject = singletonFactory.getObject();
                    newSingleton = true;
                } catch (IllegalStateException ex) {
                    // Has the singleton object implicitly appeared in the meantime ->
                    // if yes, proceed with it since the exception indicates that state.
                    // 之前有 同步 不知道什么时候会进这条分支
                    singletonObject = this.singletonObjects.get(beanName);
                    if (singletonObject == null) {
                        throw ex;
                    }
                } catch (BeanCreationException ex) {
                    // 如果创建报错了.就把之前抑制的错误一起抛出,不过这个方法里没看到有添加抑制错误的.
                    if (recordSuppressedExceptions) {
                        for (Exception suppressedException : this.suppressedExceptions) {
                            ex.addRelatedCause(suppressedException);
                        }
                    }
                    throw ex;
                } finally {
                    if (recordSuppressedExceptions) {
                        this.suppressedExceptions = null;
                    }
                    // 把之前的singletonsCurrentlyInCreation添加的正在创建的bean删掉
                    afterSingletonCreation(beanName);
                }
                // 如果是新创建了bean就添加到相应的map里
                if (newSingleton) {
                    addSingleton(beanName, singletonObject);
                }
            }
            return (singletonObject != NULL_OBJECT ? singletonObject : null);
        }
    }

    /**
     * Register an Exception that happened to get suppressed during the creation of a
     * singleton bean instance, e.g. a temporary circular reference resolution problem.
     * 添加需要抑制的错误,创建过程中如果报了这些错误,不算出错.本类中没被调用
     *
     * @param ex the Exception to register
     */
    protected void onSuppressedException(Exception ex) {
        synchronized (this.singletonObjects) {
            if (this.suppressedExceptions != null) {
                this.suppressedExceptions.add(ex);
            }
        }
    }

    /**
     * Remove the bean with the given name from the singleton cache of this factory,
     * to be able to clean up eager registration of a singleton if creation failed.
     * 移除一个单例bean
     *
     * @param beanName the name of the bean
     * @see #getSingletonMutex()
     */
    protected void removeSingleton(String beanName) {
        synchronized (this.singletonObjects) {
            this.singletonObjects.remove(beanName);
            this.singletonFactories.remove(beanName);
            this.earlySingletonObjects.remove(beanName);
            this.registeredSingletons.remove(beanName);
        }
    }

    @Override
    public boolean containsSingleton(String beanName) {
        return this.singletonObjects.containsKey(beanName);
    }

    @Override
    public String[] getSingletonNames() {
        synchronized (this.singletonObjects) {
            return StringUtils.toStringArray(this.registeredSingletons);
        }
    }

    @Override
    public int getSingletonCount() {
        synchronized (this.singletonObjects) {
            return this.registeredSingletons.size();
        }
    }


    /**
     * 设置一个bean正在被创建的标志,其实是放到一个跳过检查的set里.在这个set里的bean都会跳过检查.不然正在创建又执行创建需要抛出异常
     * @param beanName
     * @param inCreation
     */
    public void setCurrentlyInCreation(String beanName, boolean inCreation) {
        Assert.notNull(beanName, "Bean name must not be null");
        if (!inCreation) {
            this.inCreationCheckExclusions.add(beanName);
        } else {
            this.inCreationCheckExclusions.remove(beanName);
        }
    }

    public boolean isCurrentlyInCreation(String beanName) {
        Assert.notNull(beanName, "Bean name must not be null");
        return (!this.inCreationCheckExclusions.contains(beanName) && isActuallyInCreation(beanName));
    }

    /**
     * setCurrentlyInCreation方法只是用1个set集合记录需要跳过检查步骤的bean,singletonsCurrentlyInCreation里存的bean才是真正正在创建的bean
     * @param beanName
     * @return
     */
    protected boolean isActuallyInCreation(String beanName) {
        return isSingletonCurrentlyInCreation(beanName);
    }

    /**
     * Return whether the specified singleton bean is currently in creation
     * (within the entire factory).
     * 参考isActuallyInCreation方法
     *
     * @param beanName the name of the bean
     */
    public boolean isSingletonCurrentlyInCreation(String beanName) {
        return this.singletonsCurrentlyInCreation.contains(beanName);
    }

    /**
     * Callback before singleton creation.
     * <p>The default implementation register the singleton as currently in creation.
     * 在ObjectFactory创建bean之前检查一下是否已经正在创建这个bean了.
     *
     * @param beanName the name of the singleton about to be created
     * @see #isSingletonCurrentlyInCreation
     */
    protected void beforeSingletonCreation(String beanName) {
        if (!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.add(beanName)) {
            throw new BeanCurrentlyInCreationException(beanName);
        }
    }

    /**
     * Callback after singleton creation.
     * <p>The default implementation marks the singleton as not in creation anymore.
     * 在ObjectFactory创建bean之后,需要这个bean正在创建的标志移除
     *
     * @param beanName the name of the singleton that has been created
     * @see #isSingletonCurrentlyInCreation
     */
    protected void afterSingletonCreation(String beanName) {
        if (!this.inCreationCheckExclusions.contains(beanName) && !this.singletonsCurrentlyInCreation.remove(beanName)) {
            throw new IllegalStateException("Singleton '" + beanName + "' isn't currently in creation");
        }
    }


    /**
     * Add the given bean to the list of disposable beans in this registry.
     * <p>Disposable beans usually correspond to registered singletons,
     * matching the bean name but potentially being a different instance
     * (for example, a DisposableBean adapter for a singleton that does not
     * naturally implement Spring's DisposableBean interface).
     * 注册DisposableBean
     *
     * @param beanName the name of the bean
     * @param bean     the bean instance
     */
    public void registerDisposableBean(String beanName, DisposableBean bean) {
        synchronized (this.disposableBeans) {
            this.disposableBeans.put(beanName, bean);
        }
    }

    /**
     * Register a containment relationship between two beans,
     * e.g. between an inner bean and its containing outer bean.
     * <p>Also registers the containing bean as dependent on the contained bean
     * in terms of destruction order.
     * 注册嵌套的bean.我从来没用过.
     *
     * @param containedBeanName  the name of the contained (inner) bean 内部bean
     * @param containingBeanName the name of the containing (outer) bean 外部bean
     * @see #registerDependentBean
     */
    public void registerContainedBean(String containedBeanName, String containingBeanName) {
        // A quick check for an existing entry upfront, avoiding synchronization...
        Set<String> containedBeans = this.containedBeanMap.get(containingBeanName);
        if (containedBeans != null && containedBeans.contains(containedBeanName)) {
            return;
        }

        // No entry yet -> fully synchronized manipulation of the containedBeans Set
        synchronized (this.containedBeanMap) {
            containedBeans = this.containedBeanMap.get(containingBeanName);
            if (containedBeans == null) {
                containedBeans = new LinkedHashSet<String>(8);
                this.containedBeanMap.put(containingBeanName, containedBeans);
            }
            containedBeans.add(containedBeanName);
        }
        registerDependentBean(containedBeanName, containingBeanName);
    }

    /**
     * Register a dependent bean for the given bean,
     * to be destroyed before the given bean is destroyed.
     * 注册相互依赖的bean.比如A中有B.dependentBeanMap里key是B,value是A.需要先销毁A再销毁B
     * dependenciesForBeanMap刚好相反.可以参考之前成员域上的注释
     *
     * @param beanName          the name of the bean
     * @param dependentBeanName the name of the dependent bean
     */
    public void registerDependentBean(String beanName, String dependentBeanName) {
        // A quick check for an existing entry upfront, avoiding synchronization...
        // 先把别名转化到真正的bean name
        String canonicalName = canonicalName(beanName);
        Set<String> dependentBeans = this.dependentBeanMap.get(canonicalName);
        if (dependentBeans != null && dependentBeans.contains(dependentBeanName)) {
            return;
        }

        // No entry yet -> fully synchronized manipulation of the dependentBeans Set
        // 依赖之前没注册过就注册到相应的map里去
        synchronized (this.dependentBeanMap) {
            dependentBeans = this.dependentBeanMap.get(canonicalName);
            if (dependentBeans == null) {
                dependentBeans = new LinkedHashSet<String>(8);
                this.dependentBeanMap.put(canonicalName, dependentBeans);
            }
            dependentBeans.add(dependentBeanName);
        }
        synchronized (this.dependenciesForBeanMap) {
            Set<String> dependenciesForBean = this.dependenciesForBeanMap.get(dependentBeanName);
            if (dependenciesForBean == null) {
                dependenciesForBean = new LinkedHashSet<String>(8);
                this.dependenciesForBeanMap.put(dependentBeanName, dependenciesForBean);
            }
            dependenciesForBean.add(canonicalName);
        }
    }

    /**
     * Determine whether the specified dependent bean has been registered as
     * dependent on the given bean or on any of its transitive dependencies.
     * 判断2个bean是否有依赖关系
     *
     * @param beanName          the name of the bean to check
     * @param dependentBeanName the name of the dependent bean
     * @since 4.0
     */
    protected boolean isDependent(String beanName, String dependentBeanName) {
        return isDependent(beanName, dependentBeanName, null);
    }

    /**
     * 判断2个bean是否有依赖关系,A中有B,B中有C,那C依赖A是true.
     * @param beanName
     * @param dependentBeanName
     * @param alreadySeen
     * @return
     */
    private boolean isDependent(String beanName, String dependentBeanName, Set<String> alreadySeen) {
        String canonicalName = canonicalName(beanName);
        if (alreadySeen != null && alreadySeen.contains(beanName)) {
            return false;
        }
        // canonicalName是C dependentBeans是B
        Set<String> dependentBeans = this.dependentBeanMap.get(canonicalName);
        if (dependentBeans == null) {
            return false;
        }
        if (dependentBeans.contains(dependentBeanName)) {
            return true;
        }
        // 第一轮没找到A只找到包含B的一个set.所以再便利这个set.去看这个set里的bean是否依赖A,但是可能会有循环引用.所以找过的bean需要记录,不需要再找
        for (String transitiveDependency : dependentBeans) {
            if (alreadySeen == null) {
                alreadySeen = new HashSet<String>();
            }
            alreadySeen.add(beanName); // 已经找过的bean放到这里.C已经找过了.
            if (isDependent(transitiveDependency, dependentBeanName, alreadySeen)) { // 递归调用,判断B是否依赖A,是true.而C依赖B,所以C依赖A
                return true;
            }
        }
        return false;
    }

    /**
     * Determine whether a dependent bean has been registered for the given name.
     *
     * @param beanName the name of the bean to check
     */
    protected boolean hasDependentBean(String beanName) {
        return this.dependentBeanMap.containsKey(beanName);
    }

    /**
     * Return the names of all beans which depend on the specified bean, if any.
     *
     * @param beanName the name of the bean
     * @return the array of dependent bean names, or an empty array if none
     */
    public String[] getDependentBeans(String beanName) {
        Set<String> dependentBeans = this.dependentBeanMap.get(beanName);
        if (dependentBeans == null) {
            return new String[0];
        }
        return StringUtils.toStringArray(dependentBeans);
    }

    /**
     * Return the names of all beans that the specified bean depends on, if any.
     *
     * @param beanName the name of the bean
     * @return the array of names of beans which the bean depends on,
     * or an empty array if none
     */
    public String[] getDependenciesForBean(String beanName) {
        Set<String> dependenciesForBean = this.dependenciesForBeanMap.get(beanName);
        if (dependenciesForBean == null) {
            return new String[0];
        }
        return dependenciesForBean.toArray(new String[dependenciesForBean.size()]);
    }

    /**
     * 销毁单例bean
     */
    public void destroySingletons() {
        if (logger.isDebugEnabled()) {
            logger.debug("Destroying singletons in " + this);
        }
        // 设置正在销毁的标志
        synchronized (this.singletonObjects) {
            this.singletonsCurrentlyInDestruction = true;
        }

        String[] disposableBeanNames;
        synchronized (this.disposableBeans) {
            disposableBeanNames = StringUtils.toStringArray(this.disposableBeans.keySet());
        }
        // 取出所有disposableBeans然后调用每个bean都调用相应的销毁方法
        for (int i = disposableBeanNames.length - 1; i >= 0; i--) {
            destroySingleton(disposableBeanNames[i]);
        }

        // 所有缓存清空
        this.containedBeanMap.clear();
        this.dependentBeanMap.clear();
        this.dependenciesForBeanMap.clear();

        synchronized (this.singletonObjects) {
            this.singletonObjects.clear();
            this.singletonFactories.clear();
            this.earlySingletonObjects.clear();
            this.registeredSingletons.clear();
            this.singletonsCurrentlyInDestruction = false;
        }
    }

    /**
     * Destroy the given bean. Delegates to {@code destroyBean}
     * if a corresponding disposable bean instance is found.
     *
     * @param beanName the name of the bean
     * @see #destroyBean
     */
    public void destroySingleton(String beanName) {
        // Remove a registered singleton of the given name, if any.
        removeSingleton(beanName);

        // Destroy the corresponding DisposableBean instance.
        DisposableBean disposableBean;
        synchronized (this.disposableBeans) {
            disposableBean = (DisposableBean) this.disposableBeans.remove(beanName);
        }
        destroyBean(beanName, disposableBean);
    }

    /**
     * Destroy the given bean. Must destroy beans that depend on the given
     * bean before the bean itself. Should not throw any exceptions.
     *
     * @param beanName the name of the bean
     * @param bean     the bean instance to destroy
     */
    protected void destroyBean(String beanName, DisposableBean bean) {
        // Trigger destruction of dependent beans first...
        // 销毁1个bean的时候需要按顺序,先销毁引用她的bean,再销毁他自己
        Set<String> dependencies = this.dependentBeanMap.remove(beanName);
        if (dependencies != null) {
            if (logger.isDebugEnabled()) {
                logger.debug("Retrieved dependent beans for bean '" + beanName + "': " + dependencies);
            }
            for (String dependentBeanName : dependencies) {
                //对于每个引用这个bean的所有bean,先销毁他们,再销毁当前这个beanName对应的bean,A中有B需要先销毁A
                destroySingleton(dependentBeanName);
            }
        }

        // Actually destroy the bean now...
        if (bean != null) {
            try {
                bean.destroy(); // DisposableBean接口的方法
            } catch (Throwable ex) {
                logger.error("Destroy method on bean with name '" + beanName + "' threw an exception", ex);
            }
        }

        // Trigger destruction of contained beans...
        // 对于内部bean也一样,先销毁外部的bean
        Set<String> containedBeans = this.containedBeanMap.remove(beanName);
        if (containedBeans != null) {
            for (String containedBeanName : containedBeans) {
                destroySingleton(containedBeanName);
            }
        }

        // Remove destroyed bean from other beans' dependencies.
        // 销毁了这个bean,那dependentBeanMap中如果其他bean依赖这个bean,就都可以移除这个bean的引用.比如A中有B和C类.destroyB的时候需要先destroy A
        // 那destroy A了以后因为C也依赖A.所以也要把dependentBeanMap的key c 对应的vaalue A也删除,不然下次删除C的时候又要删除A.这样就重复destroy A了.
        synchronized (this.dependentBeanMap) {
            for (Iterator<Map.Entry<String, Set<String>>> it = this.dependentBeanMap.entrySet().iterator(); it.hasNext(); ) {
                Map.Entry<String, Set<String>> entry = it.next();
                Set<String> dependenciesToClean = entry.getValue();
                dependenciesToClean.remove(beanName);
                if (dependenciesToClean.isEmpty()) {
                    it.remove();
                }
            }
        }

        // Remove destroyed bean's prepared dependency information.
        this.dependenciesForBeanMap.remove(beanName);
    }

    /**
     * Exposes the singleton mutex to subclasses and external collaborators.
     * <p>Subclasses should synchronize on the given Object if they perform
     * any sort of extended singleton creation phase. In particular, subclasses
     * should <i>not</i> have their own mutexes involved in singleton creation,
     * to avoid the potential for deadlocks in lazy-init situations.
     */
    public final Object getSingletonMutex() {
        return this.singletonObjects;
    }

}

FactoryBeanRegistrySupport

这个类基本上和它的父类DefaultSingletonBeanRegistry功能差不多.就是多了1个叫做factoryBeanObjectCache的map去缓存FactoryBean生成的bean...代码写法都大同小异..我想分享下期中的1个方法

    /**
     * Obtain an object to expose from the given FactoryBean.
     *
     * @param factory           the FactoryBean instance
     * @param beanName          the name of the bean
     * @param shouldPostProcess whether the bean is subject to post-processing
     * @return the object obtained from the FactoryBean
     * @throws BeanCreationException if FactoryBean object creation failed
     * @see org.springframework.beans.factory.FactoryBean#getObject()
     */
    protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) {
        if (factory.isSingleton() && containsSingleton(beanName)) { // FactoryBean返回的对象是单例并且FactoryBean(不是返回的对象)这个bean已经在缓存中了
            synchronized (getSingletonMutex()) {
                Object object = this.factoryBeanObjectCache.get(beanName); // 从缓存里拿FactoryBean的返回对象
                if (object == null) { // 没缓存的话
                    object = doGetObjectFromFactoryBean(factory, beanName); // 就重新生成
                    // Only post-process and store if not put there already during getObject() call above
                    // (e.g. because of circular reference processing triggered by custom getBean calls)
                    Object alreadyThere = this.factoryBeanObjectCache.get(beanName); // 不懂为什么上面去过一次是null了需要再取几次...什么时候会发生呢?
                    if (alreadyThere != null) {
                        object = alreadyThere;
                    } else {
                        if (object != null && shouldPostProcess) {
                            try {
                                object = postProcessObjectFromFactoryBean(object, beanName); // 后置处理
                            } catch (Throwable ex) {
                                throw new BeanCreationException(beanName,
                                        "Post-processing of FactoryBean's singleton object failed", ex);
                            }
                        }
                        this.factoryBeanObjectCache.put(beanName, (object != null ? object : NULL_OBJECT));
                    }
                }
                return (object != NULL_OBJECT ? object : null);
            }
        } else { // 不是单例,或者第一次调用FactoryBean不再缓存中
            Object object = doGetObjectFromFactoryBean(factory, beanName); // 从FactoryBean里生成
            if (object != null && shouldPostProcess) {
                try {
                    object = postProcessObjectFromFactoryBean(object, beanName); // 后置处理
                } catch (Throwable ex) {
                    throw new BeanCreationException(beanName, "Post-processing of FactoryBean's object failed", ex);
                }
            }
            return object;
        }
    }

对比它的父类里的一些map....

factoryBeanObjectCache里存的是BeanFactory的getObject返回的对象.

singletonObjects里存一般的单例和BeanFactory对象.

然后不管是BeanFactory还是BeanFactory返回的对象.beanname都是不带&,这点和使用BeanFactory的getBean方法不太一样...等看到后面的BF可能就清楚为什么了.

另外postProcessObjectFromFactoryBean这个方法在当前类里仅仅返回传入参数object.但是是个protected的方法,子类肯定会去重写的.这个方法不出意外应该就是BeanPostProcessor参与Spring声明周期的地方(对于FactoryBean来说).

一个小测试:

package spring.bf;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.stereotype.Component;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:test-application-context.xml")
public class FactoryBeanRegistrySupportTest {

    @Autowired
    @Qualifier("factoryBeanRegistrySupportTest_FactoryBean")
    Object o;

    /**
     * 测试BeanFactory和BeanPostProcessor
     */
    @Test
    public void test1() {
        System.out.println(o);
    }
}


@Component
class FactoryBeanRegistrySupportTest_FactoryBean implements FactoryBean<Object> {

    private Object a = new Object();

    @Override
    public Object getObject() throws Exception {
        return a;
    }

    @Override
    public Class<?> getObjectType() {
        return Object.class;
    }

    @Override
    public boolean isSingleton() {
        return true;
    }
}

@Component
class FactoryBeanRegistrySupportTest_PostProcess implements BeanPostProcessor {

    private static final String name = "factoryBeanRegistrySupportTest_FactoryBean";

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if (beanName.equals(name)) {
            System.out.println("postProcessBeforeInitialization ->" + beanName);
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if (beanName.equals(name)) {
            System.out.println("postProcessAfterInitialization ->" + beanName);
        }
        return bean;
    }
}

输出:

postProcessBeforeInitialization ->factoryBeanRegistrySupportTest_FactoryBean 这个是FactoryBean作为单例被new的时候做的
postProcessAfterInitialization ->factoryBeanRegistrySupportTest_FactoryBean 这个是FactoryBean作为单例被new的时候做的
postProcessAfterInitialization ->factoryBeanRegistrySupportTest_FactoryBean 这个是FactoryBean的getObject返回的对象做的
java.lang.Object@f1e3986 输出getObject返回的对象

那么为什么FactoryBean的返回对象不要做postProcessBeforeInitialization,只做了postProcessAfterInitialization  呢??? 为什么这样设定???  不太懂.

我觉得.可能是其他bean的afterProperties可能会扫描一些特性的bean做处理..这里工厂返回的bean肯定没有被之前扫描到.而postProcessBeforeInitialization是要在afterProperties之前做的(对于单个bean来说).所以这里不再执行.

AbstractBeanFactory

/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory.support;

import org.springframework.beans.*;
import org.springframework.beans.factory.*;
import org.springframework.beans.factory.config.*;
import org.springframework.core.DecoratingClassLoader;
import org.springframework.core.NamedThreadLocal;
import org.springframework.core.convert.ConversionService;
import org.springframework.util.*;

import java.beans.PropertyEditor;
import java.security.*;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Abstract base class for {@link org.springframework.beans.factory.BeanFactory}
 * implementations, providing the full capabilities of the
 * {@link org.springframework.beans.factory.config.ConfigurableBeanFactory} SPI.
 * Does <i>not</i> assume a listable bean factory: can therefore also be used
 * as base class for bean factory implementations which obtain bean definitions
 * from some backend resource (where bean definition access is an expensive operation).
 * <p>
 * <p>This class provides a singleton cache (through its base class
 * {@link org.springframework.beans.factory.support.DefaultSingletonBeanRegistry},
 * singleton/prototype determination, {@link org.springframework.beans.factory.FactoryBean}
 * handling, aliases, bean definition merging for child bean definitions,
 * and bean destruction ({@link org.springframework.beans.factory.DisposableBean}
 * interface, custom destroy methods). Furthermore, it can manage a bean factory
 * hierarchy (delegating to the parent in case of an unknown bean), through implementing
 * the {@link org.springframework.beans.factory.HierarchicalBeanFactory} interface.
 * <p>
 * <p>The main template methods to be implemented by subclasses are
 * {@link #getBeanDefinition} and {@link #createBean}, retrieving a bean definition
 * for a given bean name and creating a bean instance for a given bean definition,
 * respectively. Default implementations of those operations can be found in
 * {@link DefaultListableBeanFactory} and {@link AbstractAutowireCapableBeanFactory}.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Costin Leau
 * @author Chris Beams
 * @see #getBeanDefinition
 * @see #createBean
 * @see AbstractAutowireCapableBeanFactory#createBean
 * @see DefaultListableBeanFactory#getBeanDefinition
 * @since 15 April 2001
 */
public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {

    /**
     * Parent bean factory, for bean inheritance support
     */
    private BeanFactory parentBeanFactory;

    /**
     * ClassLoader to resolve bean class names with, if necessary
     */
    private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

    /**
     * ClassLoader to temporarily resolve bean class names with, if necessary
     */
    private ClassLoader tempClassLoader;

    /**
     * Whether to cache bean metadata or rather reobtain it for every access
     */
    private boolean cacheBeanMetadata = true;

    /**
     * Resolution strategy for expressions in bean definition values
     */
    private BeanExpressionResolver beanExpressionResolver;

    /**
     * Spring ConversionService to use instead of PropertyEditors
     */
    private ConversionService conversionService;

    /**
     * Custom PropertyEditorRegistrars to apply to the beans of this factory
     */
    private final Set<PropertyEditorRegistrar> propertyEditorRegistrars =
            new LinkedHashSet<PropertyEditorRegistrar>(4);

    /**
     * A custom TypeConverter to use, overriding the default PropertyEditor mechanism
     */
    private TypeConverter typeConverter;

    /**
     * Custom PropertyEditors to apply to the beans of this factory
     */
    private final Map<Class<?>, Class<? extends PropertyEditor>> customEditors =
            new HashMap<Class<?>, Class<? extends PropertyEditor>>(4);

    /**
     * String resolvers to apply e.g. to annotation attribute values
     */
    private final List<StringValueResolver> embeddedValueResolvers = new LinkedList<StringValueResolver>();

    /**
     * BeanPostProcessors to apply in createBean
     */
    private final List<BeanPostProcessor> beanPostProcessors = new ArrayList<BeanPostProcessor>();

    /**
     * Indicates whether any InstantiationAwareBeanPostProcessors have been registered
     */
    private boolean hasInstantiationAwareBeanPostProcessors;

    /**
     * Indicates whether any DestructionAwareBeanPostProcessors have been registered
     */
    private boolean hasDestructionAwareBeanPostProcessors;

    /**
     * Map from scope identifier String to corresponding Scope
     */
    private final Map<String, Scope> scopes = new LinkedHashMap<String, Scope>(8);

    /**
     * Security context used when running with a SecurityManager
     */
    private SecurityContextProvider securityContextProvider;

    /**
     * Map from bean name to merged RootBeanDefinition
     */
    private final Map<String, RootBeanDefinition> mergedBeanDefinitions =
            new ConcurrentHashMap<String, RootBeanDefinition>(64);

    /**
     * Names of beans that have already been created at least once
     */
    private final Set<String> alreadyCreated = Collections.newSetFromMap(new ConcurrentHashMap<String, Boolean>(64));

    /**
     * Names of beans that are currently in creation
     */
    private final ThreadLocal<Object> prototypesCurrentlyInCreation =
            new NamedThreadLocal<Object>("Prototype beans currently in creation");


    /**
     * Create a new AbstractBeanFactory.
     */
    public AbstractBeanFactory() {
    }

    /**
     * Create a new AbstractBeanFactory with the given parent.
     *
     * @param parentBeanFactory parent bean factory, or {@code null} if none
     * @see #getBean
     */
    public AbstractBeanFactory(BeanFactory parentBeanFactory) {
        this.parentBeanFactory = parentBeanFactory;
    }


    //---------------------------------------------------------------------
    // Implementation of BeanFactory interface
    //---------------------------------------------------------------------

    @Override
    public Object getBean(String name) throws BeansException {
        return doGetBean(name, null, null, false);
    }

    @Override
    public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
        return doGetBean(name, requiredType, null, false);
    }

    @Override
    public Object getBean(String name, Object... args) throws BeansException {
        return doGetBean(name, null, args, false);
    }

    /**
     * Return an instance, which may be shared or independent, of the specified bean.
     *
     * @param name         the name of the bean to retrieve
     * @param requiredType the required type of the bean to retrieve
     * @param args         arguments to use when creating a bean instance using explicit arguments
     *                     (only applied when creating a new instance as opposed to retrieving an existing one)
     * @return an instance of the bean
     * @throws BeansException if the bean could not be created
     */
    public <T> T getBean(String name, Class<T> requiredType, Object... args) throws BeansException {
        return doGetBean(name, requiredType, args, false);
    }

    /**
     * Return an instance, which may be shared or independent, of the specified bean.
     *
     * @param name          the name of the bean to retrieve
     * @param requiredType  the required type of the bean to retrieve
     * @param args          arguments to use when creating a bean instance using explicit arguments
     *                      (only applied when creating a new instance as opposed to retrieving an existing one)
     * @param typeCheckOnly whether the instance is obtained for a type check,
     *                      not for actual use
     * @return an instance of the bean
     * @throws BeansException if the bean could not be created
     */
    @SuppressWarnings("unchecked")
    protected <T> T doGetBean(final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException {

        // 别名转化成bean的名字,同时有&的话直接去掉
        final String beanName = transformedBeanName(name);
        Object bean;

        // Eagerly check singleton cache for manually registered singletons.
        // 可能会是FactoryBean
        Object sharedInstance = getSingleton(beanName);
        if (sharedInstance != null && args == null) {
            if (logger.isDebugEnabled()) {
                if (isSingletonCurrentlyInCreation(beanName)) {
                    logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
                            "' that is not fully initialized yet - a consequence of a circular reference");
                } else {
                    logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
                }
            }
            // 如果是FactoryBean就调用getObject,否则就返回那个bean
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
        } else { // 有可能是prototype bean
            // Fail if we're already creating this bean instance:
            // We're assumably within a circular reference.
            // 如果当前线程已经在创建个bean了.就抛出异常
            if (isPrototypeCurrentlyInCreation(beanName)) {
                throw new BeanCurrentlyInCreationException(beanName);
            }

            // Check if bean definition exists in this factory.
            BeanFactory parentBeanFactory = getParentBeanFactory();
            // 如果这个bean的配置定义在父BF中的,即当前BF没有这个bean的配置信息
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                // Not found -> check parent.
                // 转化别名成bean的实际名字,但是不会去掉&
                String nameToLookup = originalBeanName(name);
                // 调用父BF的getBean方法去获取bean.
                if (args != null) {
                    // Delegation to parent with explicit args.
                    return (T) parentBeanFactory.getBean(nameToLookup, args);
                } else {
                    // No args -> delegate to standard getBean method.
                    return parentBeanFactory.getBean(nameToLookup, requiredType);
                }
            }

            if (!typeCheckOnly) {
                // 标记这个bean已被创建
                markBeanAsCreated(beanName);
            }

            try {
                // 获取BeanDefinition
                final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
                // 检测这个bean是不是abstract的
                checkMergedBeanDefinition(mbd, beanName, args);

                // Guarantee initialization of beans that the current bean depends on.
                // A中有B,C,dependsOn=B,C
                String[] dependsOn = mbd.getDependsOn();
                if (dependsOn != null) {
                    for (String dependsOnBean : dependsOn) { // B和C
                        // 如果dependsOnBean中有beanName域.而mbd.getDependsOn();说明beanName中有dependsOnBean,所以是相互依赖
                        if (isDependent(beanName, dependsOnBean)) { // 为true说明B,C中也有A,而外层的mbd.getDependsOn();说明A中有B,C,所以循环引用
                            throw new BeanCreationException(mbd.getResourceDescription(), beanName,
                                    "Circular depends-on relationship between '" + beanName + "' and '" + dependsOnBean + "'");
                        }
                        // beanName中有dependsOnBean,beanName依赖于dependsOnBean
                        registerDependentBean(dependsOnBean, beanName);
                        // 先初始化成员域的bean
                        getBean(dependsOnBean);
                    }
                }

                // Create bean instance.
                // 如果是单例
                if (mbd.isSingleton()) {
                    // 获取这个bean,没创建就创建
                    sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
                        @Override
                        public Object getObject() throws BeansException {
                            try {
                                return createBean(beanName, mbd, args);
                            } catch (BeansException ex) {
                                // Explicitly remove instance from singleton cache: It might have been put there
                                // eagerly by the creation process, to allow for circular reference resolution.
                                // Also remove any beans that received a temporary reference to the bean.
                                destroySingleton(beanName);
                                throw ex;
                            }
                        }
                    });
                    // 如果是FactoryBean就调用getObject,否则就返回那个bean
                    bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
                } else if (mbd.isPrototype()) { // 如果是原型bean
                    // It's a prototype -> create a new instance.
                    Object prototypeInstance = null;
                    try {
                        // 记录正在创建的原型bean,这个bean和线程绑定
                        beforePrototypeCreation(beanName);
                        prototypeInstance = createBean(beanName, mbd, args);
                    } finally {
                        // 创建完毕,移除这个标记
                        afterPrototypeCreation(beanName);
                    }
                    // 如果是FactoryBean就调用getObject,否则就返回那个bean
                    bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
                } else {
                    // 既不是单例又不是原型
                    String scopeName = mbd.getScope();
                    final Scope scope = this.scopes.get(scopeName);
                    if (scope == null) {
                        throw new IllegalStateException("No Scope registered for scope '" + scopeName + "'");
                    }
                    try {
                        Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
                            @Override
                            public Object getObject() throws BeansException {
                                beforePrototypeCreation(beanName);
                                try {
                                    return createBean(beanName, mbd, args);
                                } finally {
                                    afterPrototypeCreation(beanName);
                                }
                            }
                        });
                        bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
                    } catch (IllegalStateException ex) {
                        throw new BeanCreationException(beanName,
                                "Scope '" + scopeName + "' is not active for the current thread; " +
                                        "consider defining a scoped proxy for this bean if you intend to refer to it from a singleton",
                                ex);
                    }
                }
            } catch (BeansException ex) {
                // 创建出错.
                // 因为之前调用过markBeanAsCreated(beanName);标记过bean被创建,实际是失败的,所以要移除这个标记
                cleanupAfterBeanCreationFailure(beanName);
                throw ex;
            }
        }

        // Check if required type matches the type of the actual bean instance.
        // 讲前面得到的bean进行类型转化并返回
        if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
            try {
                return getTypeConverter().convertIfNecessary(bean, requiredType);
            } catch (TypeMismatchException ex) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Failed to convert bean '" + name + "' to required type [" +
                            ClassUtils.getQualifiedName(requiredType) + "]", ex);
                }
                throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
            }
        }
        return (T) bean;
    }

    @Override
    public boolean containsBean(String name) {
        String beanName = transformedBeanName(name);
        if (containsSingleton(beanName) || containsBeanDefinition(beanName)) {
            // &开头或者是FactoryBean的实例
            return (!BeanFactoryUtils.isFactoryDereference(name) || isFactoryBean(name));
        }
        // Not found -> check parent.
        // 本BF找不到就找父类的
        BeanFactory parentBeanFactory = getParentBeanFactory();
        return (parentBeanFactory != null && parentBeanFactory.containsBean(originalBeanName(name)));
    }

    @Override
    public boolean isSingleton(String name) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name); // 去掉&并且将alias转化成真正的beanname

        Object beanInstance = getSingleton(beanName, false); // 取到singleton
        if (beanInstance != null) {
            if (beanInstance instanceof FactoryBean) { // 如果bean是FactoryBean.
                // &开头为true(取工厂bean)或者FactoryBean的isSingleton返回为true(不是&开头,取工厂的getObject返回)
                return (BeanFactoryUtils.isFactoryDereference(name) || ((FactoryBean<?>) beanInstance).isSingleton());
            } else { // 不是工厂bean的情况下,不是&开头返回ture,就是最一般的单例bean.
                return !BeanFactoryUtils.isFactoryDereference(name);
            }
        } else if (containsSingleton(beanName)) { // 不知道什么时候会进,getSingleton,但是containsSingleton为true.可能是abstract的bean吧
            return true;
        } else {
            // No singleton instance found -> check bean definition.
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                // No bean definition found in this factory -> delegate to parent.
                // 本BF没有这个bean的定义的话可以去找父类的.
                return parentBeanFactory.isSingleton(originalBeanName(name));
            }

            // 合并父类和本身的bean定义
            RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);

            // In case of FactoryBean, return singleton status of created object if not a dereference.
            if (mbd.isSingleton()) { // 定义中是单例,在判断是不是工厂
                if (isFactoryBean(beanName, mbd)) { // 是工厂的话并且是不带&的话需要调用工厂的isSingleton方法
                    if (BeanFactoryUtils.isFactoryDereference(name)) {
                        return true;
                    }
                    FactoryBean<?> factoryBean = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                    return factoryBean.isSingleton();
                } else { // 不是工厂bean就是true
                    return !BeanFactoryUtils.isFactoryDereference(name);
                }
            } else {
                return false;
            }
        }
    }

    @Override
    public boolean isPrototype(String name) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name);

        BeanFactory parentBeanFactory = getParentBeanFactory();
        if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
            // No bean definition found in this factory -> delegate to parent.
            // 本BF中没有这个bean的定义就找父工厂
            return parentBeanFactory.isPrototype(originalBeanName(name));
        }

        // 合并父BF和本BF得到bean的定义
        RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
        if (mbd.isPrototype()) { // bean的定义是原型,并且取不带&的bean,那就是原型对象为true,如果取&的bean,那需要返回的是工厂,如果是FactoryBean
            // In case of FactoryBean, return singleton status of created object if not a dereference.
            return (!BeanFactoryUtils.isFactoryDereference(name) || isFactoryBean(beanName, mbd));
        } else {
            // Singleton or scoped - not a prototype.
            // However, FactoryBean may still produce a prototype object...
            // 如果是&开头取工厂就直接返回false
            if (BeanFactoryUtils.isFactoryDereference(name)) {
                return false;
            }
            // 不是&开头的话要看工厂的isSingleton或者isPrototype
            if (isFactoryBean(beanName, mbd)) {
                final FactoryBean<?> factoryBean = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                if (System.getSecurityManager() != null) {
                    return AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
                        @Override
                        public Boolean run() {
                            return ((factoryBean instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factoryBean).isPrototype()) ||
                                    !factoryBean.isSingleton());
                        }
                    }, getAccessControlContext());
                } else {
                    return ((factoryBean instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factoryBean).isPrototype()) ||
                            !factoryBean.isSingleton());
                }
            } else {
                return false;
            }
        }
    }

    @Override
    public boolean isTypeMatch(String name, Class<?> targetType) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name);
        Class<?> typeToMatch = (targetType != null ? targetType : Object.class);

        // Check manually registered singletons.
        Object beanInstance = getSingleton(beanName, false);
        if (beanInstance != null) {
            if (beanInstance instanceof FactoryBean) {
                if (!BeanFactoryUtils.isFactoryDereference(name)) { // 取工厂的返回
                    Class<?> type = getTypeForFactoryBean((FactoryBean<?>) beanInstance);
                    return (type != null && ClassUtils.isAssignable(typeToMatch, type));
                } else { // 取工厂bean
                    return ClassUtils.isAssignableValue(typeToMatch, beanInstance);
                }
            } else { // 取一般的bean
                return !BeanFactoryUtils.isFactoryDereference(name) &&
                        ClassUtils.isAssignableValue(typeToMatch, beanInstance);
            }
        } else if (containsSingleton(beanName) && !containsBeanDefinition(beanName)) {
            // null instance registered
            return false;
        } else {
            // No singleton instance found -> check bean definition.
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                // No bean definition found in this factory -> delegate to parent.
                return parentBeanFactory.isTypeMatch(originalBeanName(name), targetType);
            }

            // Retrieve corresponding bean definition.
            RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);

            Class<?>[] typesToMatch = (FactoryBean.class.equals(typeToMatch) ?
                    new Class<?>[]{typeToMatch} : new Class<?>[]{FactoryBean.class, typeToMatch});

            // Check decorated bean definition, if any: We assume it'll be easier
            // to determine the decorated bean's type than the proxy's type.
            BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();
            if (dbd != null && !BeanFactoryUtils.isFactoryDereference(name)) {
                RootBeanDefinition tbd = getMergedBeanDefinition(dbd.getBeanName(), dbd.getBeanDefinition(), mbd);
                Class<?> targetClass = predictBeanType(dbd.getBeanName(), tbd, typesToMatch);
                if (targetClass != null && !FactoryBean.class.isAssignableFrom(targetClass)) {
                    return typeToMatch.isAssignableFrom(targetClass);
                }
            }

            Class<?> beanType = predictBeanType(beanName, mbd, typesToMatch);
            if (beanType == null) {
                return false;
            }

            // Check bean class whether we're dealing with a FactoryBean.
            if (FactoryBean.class.isAssignableFrom(beanType)) {
                if (!BeanFactoryUtils.isFactoryDereference(name)) {
                    // If it's a FactoryBean, we want to look at what it creates, not the factory class.
                    beanType = getTypeForFactoryBean(beanName, mbd);
                    if (beanType == null) {
                        return false;
                    }
                }
            } else if (BeanFactoryUtils.isFactoryDereference(name)) {
                // Special case: A SmartInstantiationAwareBeanPostProcessor returned a non-FactoryBean
                // type but we nevertheless are being asked to dereference a FactoryBean...
                // Let's check the original bean class and proceed with it if it is a FactoryBean.
                beanType = predictBeanType(beanName, mbd, FactoryBean.class);
                if (beanType == null || !FactoryBean.class.isAssignableFrom(beanType)) {
                    return false;
                }
            }

            return typeToMatch.isAssignableFrom(beanType);
        }
    }

    @Override
    public Class<?> getType(String name) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name);

        // Check manually registered singletons.
        Object beanInstance = getSingleton(beanName, false);
        if (beanInstance != null) {
            if (beanInstance instanceof FactoryBean && !BeanFactoryUtils.isFactoryDereference(name)) {
                return getTypeForFactoryBean((FactoryBean<?>) beanInstance);
            } else {
                return beanInstance.getClass();
            }
        } else if (containsSingleton(beanName) && !containsBeanDefinition(beanName)) {
            // null instance registered
            return null;
        } else {
            // No singleton instance found -> check bean definition.
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                // No bean definition found in this factory -> delegate to parent.
                return parentBeanFactory.getType(originalBeanName(name));
            }

            RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);

            // Check decorated bean definition, if any: We assume it'll be easier
            // to determine the decorated bean's type than the proxy's type.
            BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();
            if (dbd != null && !BeanFactoryUtils.isFactoryDereference(name)) {
                RootBeanDefinition tbd = getMergedBeanDefinition(dbd.getBeanName(), dbd.getBeanDefinition(), mbd);
                Class<?> targetClass = predictBeanType(dbd.getBeanName(), tbd);
                if (targetClass != null && !FactoryBean.class.isAssignableFrom(targetClass)) {
                    return targetClass;
                }
            }

            Class<?> beanClass = predictBeanType(beanName, mbd);

            // Check bean class whether we're dealing with a FactoryBean.
            if (beanClass != null && FactoryBean.class.isAssignableFrom(beanClass)) {
                if (!BeanFactoryUtils.isFactoryDereference(name)) {
                    // If it's a FactoryBean, we want to look at what it creates, not at the factory class.
                    return getTypeForFactoryBean(beanName, mbd);
                } else {
                    return beanClass;
                }
            } else {
                return (!BeanFactoryUtils.isFactoryDereference(name) ? beanClass : null);
            }
        }
    }

    /**
     * 覆盖了父类方法,增加了对FactoryBean的支持
     *
     * @param name
     * @return
     */
    @Override
    public String[] getAliases(String name) {
        String beanName = transformedBeanName(name);
        List<String> aliases = new ArrayList<String>();
        boolean factoryPrefix = name.startsWith(FACTORY_BEAN_PREFIX);
        String fullBeanName = beanName;
        if (factoryPrefix) {
            fullBeanName = FACTORY_BEAN_PREFIX + beanName;
        }
        if (!fullBeanName.equals(name)) {
            aliases.add(fullBeanName);
        }
        String[] retrievedAliases = super.getAliases(beanName);
        for (String retrievedAlias : retrievedAliases) {
            String alias = (factoryPrefix ? FACTORY_BEAN_PREFIX : "") + retrievedAlias;
            if (!alias.equals(name)) {
                aliases.add(alias);
            }
        }
        if (!containsSingleton(beanName) && !containsBeanDefinition(beanName)) {
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null) {
                aliases.addAll(Arrays.asList(parentBeanFactory.getAliases(fullBeanName)));
            }
        }
        return StringUtils.toStringArray(aliases);
    }


    //---------------------------------------------------------------------
    // Implementation of HierarchicalBeanFactory interface
    //---------------------------------------------------------------------

    @Override
    public BeanFactory getParentBeanFactory() {
        return this.parentBeanFactory;
    }

    @Override
    public boolean containsLocalBean(String name) {
        String beanName = transformedBeanName(name);
        return ((containsSingleton(beanName) || containsBeanDefinition(beanName)) &&
                (!BeanFactoryUtils.isFactoryDereference(name) || isFactoryBean(beanName)));
    }


    //---------------------------------------------------------------------
    // Implementation of ConfigurableBeanFactory interface
    //---------------------------------------------------------------------

    @Override
    public void setParentBeanFactory(BeanFactory parentBeanFactory) {
        if (this.parentBeanFactory != null && this.parentBeanFactory != parentBeanFactory) {
            throw new IllegalStateException("Already associated with parent BeanFactory: " + this.parentBeanFactory);
        }
        this.parentBeanFactory = parentBeanFactory;
    }

    @Override
    public void setBeanClassLoader(ClassLoader beanClassLoader) {
        this.beanClassLoader = (beanClassLoader != null ? beanClassLoader : ClassUtils.getDefaultClassLoader());
    }

    @Override
    public ClassLoader getBeanClassLoader() {
        return this.beanClassLoader;
    }

    @Override
    public void setTempClassLoader(ClassLoader tempClassLoader) {
        this.tempClassLoader = tempClassLoader;
    }

    @Override
    public ClassLoader getTempClassLoader() {
        return this.tempClassLoader;
    }

    @Override
    public void setCacheBeanMetadata(boolean cacheBeanMetadata) {
        this.cacheBeanMetadata = cacheBeanMetadata;
    }

    @Override
    public boolean isCacheBeanMetadata() {
        return this.cacheBeanMetadata;
    }

    @Override
    public void setBeanExpressionResolver(BeanExpressionResolver resolver) {
        this.beanExpressionResolver = resolver;
    }

    @Override
    public BeanExpressionResolver getBeanExpressionResolver() {
        return this.beanExpressionResolver;
    }

    @Override
    public void setConversionService(ConversionService conversionService) {
        this.conversionService = conversionService;
    }

    @Override
    public ConversionService getConversionService() {
        return this.conversionService;
    }

    @Override
    public void addPropertyEditorRegistrar(PropertyEditorRegistrar registrar) {
        Assert.notNull(registrar, "PropertyEditorRegistrar must not be null");
        this.propertyEditorRegistrars.add(registrar);
    }

    /**
     * Return the set of PropertyEditorRegistrars.
     */
    public Set<PropertyEditorRegistrar> getPropertyEditorRegistrars() {
        return this.propertyEditorRegistrars;
    }

    @Override
    public void registerCustomEditor(Class<?> requiredType, Class<? extends PropertyEditor> propertyEditorClass) {
        Assert.notNull(requiredType, "Required type must not be null");
        Assert.isAssignable(PropertyEditor.class, propertyEditorClass);
        this.customEditors.put(requiredType, propertyEditorClass);
    }

    @Override
    public void copyRegisteredEditorsTo(PropertyEditorRegistry registry) {
        registerCustomEditors(registry);
    }

    /**
     * Return the map of custom editors, with Classes as keys and PropertyEditor classes as values.
     */
    public Map<Class<?>, Class<? extends PropertyEditor>> getCustomEditors() {
        return this.customEditors;
    }

    @Override
    public void setTypeConverter(TypeConverter typeConverter) {
        this.typeConverter = typeConverter;
    }

    /**
     * Return the custom TypeConverter to use, if any.
     *
     * @return the custom TypeConverter, or {@code null} if none specified
     */
    protected TypeConverter getCustomTypeConverter() {
        return this.typeConverter;
    }

    @Override
    public TypeConverter getTypeConverter() {
        TypeConverter customConverter = getCustomTypeConverter();
        if (customConverter != null) {
            return customConverter;
        } else {
            // Build default TypeConverter, registering custom editors.
            SimpleTypeConverter typeConverter = new SimpleTypeConverter();
            typeConverter.setConversionService(getConversionService());
            registerCustomEditors(typeConverter);
            return typeConverter;
        }
    }

    @Override
    public void addEmbeddedValueResolver(StringValueResolver valueResolver) {
        Assert.notNull(valueResolver, "StringValueResolver must not be null");
        this.embeddedValueResolvers.add(valueResolver);
    }

    @Override
    public String resolveEmbeddedValue(String value) {
        String result = value;
        for (StringValueResolver resolver : this.embeddedValueResolvers) {
            if (result == null) {
                return null;
            }
            result = resolver.resolveStringValue(result);
        }
        return result;
    }

    @Override
    public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
        Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
        this.beanPostProcessors.remove(beanPostProcessor);
        this.beanPostProcessors.add(beanPostProcessor);
        if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
            this.hasInstantiationAwareBeanPostProcessors = true;
        }
        if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) {
            this.hasDestructionAwareBeanPostProcessors = true;
        }
    }

    @Override
    public int getBeanPostProcessorCount() {
        return this.beanPostProcessors.size();
    }

    /**
     * Return the list of BeanPostProcessors that will get applied
     * to beans created with this factory.
     */
    public List<BeanPostProcessor> getBeanPostProcessors() {
        return this.beanPostProcessors;
    }

    /**
     * Return whether this factory holds a InstantiationAwareBeanPostProcessor
     * that will get applied to singleton beans on shutdown.
     *
     * @see #addBeanPostProcessor
     * @see org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor
     */
    protected boolean hasInstantiationAwareBeanPostProcessors() {
        return this.hasInstantiationAwareBeanPostProcessors;
    }

    /**
     * Return whether this factory holds a DestructionAwareBeanPostProcessor
     * that will get applied to singleton beans on shutdown.
     *
     * @see #addBeanPostProcessor
     * @see org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor
     */
    protected boolean hasDestructionAwareBeanPostProcessors() {
        return this.hasDestructionAwareBeanPostProcessors;
    }

    @Override
    public void registerScope(String scopeName, Scope scope) {
        Assert.notNull(scopeName, "Scope identifier must not be null");
        Assert.notNull(scope, "Scope must not be null");
        if (SCOPE_SINGLETON.equals(scopeName) || SCOPE_PROTOTYPE.equals(scopeName)) {
            throw new IllegalArgumentException("Cannot replace existing scopes 'singleton' and 'prototype'");
        }
        Scope previous = this.scopes.put(scopeName, scope);
        if (previous != null && previous != scope) {
            if (logger.isInfoEnabled()) {
                logger.info("Replacing scope '" + scopeName + "' from [" + previous + "] to [" + scope + "]");
            }
        } else {
            if (logger.isDebugEnabled()) {
                logger.debug("Registering scope '" + scopeName + "' with implementation [" + scope + "]");
            }
        }
    }

    @Override
    public String[] getRegisteredScopeNames() {
        return StringUtils.toStringArray(this.scopes.keySet());
    }

    @Override
    public Scope getRegisteredScope(String scopeName) {
        Assert.notNull(scopeName, "Scope identifier must not be null");
        return this.scopes.get(scopeName);
    }

    /**
     * Set the security context provider for this bean factory. If a security manager
     * is set, interaction with the user code will be executed using the privileged
     * of the provided security context.
     */
    public void setSecurityContextProvider(SecurityContextProvider securityProvider) {
        this.securityContextProvider = securityProvider;
    }

    /**
     * Delegate the creation of the access control context to the
     * {@link #setSecurityContextProvider SecurityContextProvider}.
     */
    @Override
    public AccessControlContext getAccessControlContext() {
        return (this.securityContextProvider != null ?
                this.securityContextProvider.getAccessControlContext() :
                AccessController.getContext());
    }

    @Override
    public void copyConfigurationFrom(ConfigurableBeanFactory otherFactory) {
        Assert.notNull(otherFactory, "BeanFactory must not be null");
        setBeanClassLoader(otherFactory.getBeanClassLoader());
        setCacheBeanMetadata(otherFactory.isCacheBeanMetadata());
        setBeanExpressionResolver(otherFactory.getBeanExpressionResolver());
        if (otherFactory instanceof AbstractBeanFactory) {
            AbstractBeanFactory otherAbstractFactory = (AbstractBeanFactory) otherFactory;
            this.customEditors.putAll(otherAbstractFactory.customEditors);
            this.propertyEditorRegistrars.addAll(otherAbstractFactory.propertyEditorRegistrars);
            this.beanPostProcessors.addAll(otherAbstractFactory.beanPostProcessors);
            this.hasInstantiationAwareBeanPostProcessors = this.hasInstantiationAwareBeanPostProcessors ||
                    otherAbstractFactory.hasInstantiationAwareBeanPostProcessors;
            this.hasDestructionAwareBeanPostProcessors = this.hasDestructionAwareBeanPostProcessors ||
                    otherAbstractFactory.hasDestructionAwareBeanPostProcessors;
            this.scopes.putAll(otherAbstractFactory.scopes);
            this.securityContextProvider = otherAbstractFactory.securityContextProvider;
        } else {
            setTypeConverter(otherFactory.getTypeConverter());
        }
    }

    /**
     * Return a 'merged' BeanDefinition for the given bean name,
     * merging a child bean definition with its parent if necessary.
     * <p>This {@code getMergedBeanDefinition} considers bean definition
     * in ancestors as well.
     *
     * @param name the name of the bean to retrieve the merged definition for
     *             (may be an alias)
     * @return a (potentially merged) RootBeanDefinition for the given bean
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @throws BeanDefinitionStoreException  in case of an invalid bean definition
     */
    @Override
    public BeanDefinition getMergedBeanDefinition(String name) throws BeansException {
        String beanName = transformedBeanName(name);

        // Efficiently check whether bean definition exists in this factory.
        if (!containsBeanDefinition(beanName) && getParentBeanFactory() instanceof ConfigurableBeanFactory) {
            return ((ConfigurableBeanFactory) getParentBeanFactory()).getMergedBeanDefinition(beanName);
        }
        // Resolve merged bean definition locally.
        return getMergedLocalBeanDefinition(beanName);
    }

    @Override
    public boolean isFactoryBean(String name) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name);

        Object beanInstance = getSingleton(beanName, false);
        if (beanInstance != null) {
            return (beanInstance instanceof FactoryBean);
        } else if (containsSingleton(beanName)) {
            // 可能这个bean不允许被创建(abstract的bean)?
            // null instance registered
            return false;
        }

        // No singleton instance found -> check bean definition.
        if (!containsBeanDefinition(beanName) && getParentBeanFactory() instanceof ConfigurableBeanFactory) {
            // No bean definition found in this factory -> delegate to parent.
            // 本BF没有就找父类的
            return ((ConfigurableBeanFactory) getParentBeanFactory()).isFactoryBean(name);
        }

        return isFactoryBean(beanName, getMergedLocalBeanDefinition(beanName));
    }

    @Override
    public boolean isActuallyInCreation(String beanName) {
        return (isSingletonCurrentlyInCreation(beanName) || isPrototypeCurrentlyInCreation(beanName));
    }

    /**
     * Return whether the specified prototype bean is currently in creation
     * (within the current thread).
     *
     * @param beanName the name of the bean
     */
    protected boolean isPrototypeCurrentlyInCreation(String beanName) {
        Object curVal = this.prototypesCurrentlyInCreation.get();
        return (curVal != null &&
                (curVal.equals(beanName) || (curVal instanceof Set && ((Set<?>) curVal).contains(beanName))));
    }

    /**
     * Callback before prototype creation.
     * 将正在创建的额原型bean放到threadlocal中,1个原型bean的类在1个线程中只能有1个正在创建的实例
     * <p>The default implementation register the prototype as currently in creation.
     *
     * @param beanName the name of the prototype about to be created
     * @see #isPrototypeCurrentlyInCreation
     */
    @SuppressWarnings("unchecked")
    protected void beforePrototypeCreation(String beanName) {
        Object curVal = this.prototypesCurrentlyInCreation.get();
        if (curVal == null) {
            this.prototypesCurrentlyInCreation.set(beanName);
        } else if (curVal instanceof String) {
            Set<String> beanNameSet = new HashSet<String>(2);
            beanNameSet.add((String) curVal);
            beanNameSet.add(beanName);
            this.prototypesCurrentlyInCreation.set(beanNameSet);
        } else {
            Set<String> beanNameSet = (Set<String>) curVal;
            beanNameSet.add(beanName);
        }
    }

    /**
     * Callback after prototype creation.
     * 将之前线程变量中存着的正在创建的原型bean移除,因为已经创建完毕
     * <p>The default implementation marks the prototype as not in creation anymore.
     *
     * @param beanName the name of the prototype that has been created
     * @see #isPrototypeCurrentlyInCreation
     */
    @SuppressWarnings("unchecked")
    protected void afterPrototypeCreation(String beanName) {
        Object curVal = this.prototypesCurrentlyInCreation.get();
        if (curVal instanceof String) {
            this.prototypesCurrentlyInCreation.remove();
        } else if (curVal instanceof Set) {
            Set<String> beanNameSet = (Set<String>) curVal;
            beanNameSet.remove(beanName);
            if (beanNameSet.isEmpty()) {
                this.prototypesCurrentlyInCreation.remove();
            }
        }
    }

    @Override
    public void destroyBean(String beanName, Object beanInstance) {
        destroyBean(beanName, beanInstance, getMergedLocalBeanDefinition(beanName));
    }

    /**
     * Destroy the given bean instance (usually a prototype instance
     * obtained from this factory) according to the given bean definition.
     *
     * @param beanName     the name of the bean definition
     * @param beanInstance the bean instance to destroy
     * @param mbd          the merged bean definition
     */
    protected void destroyBean(String beanName, Object beanInstance, RootBeanDefinition mbd) {
        new DisposableBeanAdapter(beanInstance, beanName, mbd, getBeanPostProcessors(), getAccessControlContext()).destroy();
    }

    @Override
    public void destroyScopedBean(String beanName) {
        RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
        if (mbd.isSingleton() || mbd.isPrototype()) {
            throw new IllegalArgumentException(
                    "Bean name '" + beanName + "' does not correspond to an object in a mutable scope");
        }
        String scopeName = mbd.getScope();
        Scope scope = this.scopes.get(scopeName);
        if (scope == null) {
            throw new IllegalStateException("No Scope SPI registered for scope '" + scopeName + "'");
        }
        Object bean = scope.remove(beanName);
        if (bean != null) {
            destroyBean(beanName, bean, mbd);
        }
    }


    //---------------------------------------------------------------------
    // Implementation methods
    //---------------------------------------------------------------------

    /**
     * Return the bean name, stripping out the factory dereference prefix if necessary,
     * and resolving aliases to canonical names.
     * 去掉&前缀,并且把alias->真正的beanname
     *
     * @param name the user-specified name
     * @return the transformed bean name
     */
    protected String transformedBeanName(String name) {
        return canonicalName(BeanFactoryUtils.transformedBeanName(name));
    }

    /**
     * Determine the original bean name, resolving locally defined aliases to canonical names.
     *
     * @param name the user-specified name
     * @return the original bean name
     */
    protected String originalBeanName(String name) {
        String beanName = transformedBeanName(name);
        if (name.startsWith(FACTORY_BEAN_PREFIX)) {
            beanName = FACTORY_BEAN_PREFIX + beanName;
        }
        return beanName;
    }

    /**
     * Initialize the given BeanWrapper with the custom editors registered
     * with this factory. To be called for BeanWrappers that will create
     * and populate bean instances.
     * <p>The default implementation delegates to {@link #registerCustomEditors}.
     * Can be overridden in subclasses.
     *
     * @param bw the BeanWrapper to initialize
     */
    protected void initBeanWrapper(BeanWrapper bw) {
        bw.setConversionService(getConversionService());
        registerCustomEditors(bw);
    }

    /**
     * Initialize the given PropertyEditorRegistry with the custom editors
     * that have been registered with this BeanFactory.
     * <p>To be called for BeanWrappers that will create and populate bean
     * instances, and for SimpleTypeConverter used for constructor argument
     * and factory method type conversion.
     *
     * @param registry the PropertyEditorRegistry to initialize
     */
    protected void registerCustomEditors(PropertyEditorRegistry registry) {
        PropertyEditorRegistrySupport registrySupport =
                (registry instanceof PropertyEditorRegistrySupport ? (PropertyEditorRegistrySupport) registry : null);
        if (registrySupport != null) {
            registrySupport.useConfigValueEditors();
        }
        if (!this.propertyEditorRegistrars.isEmpty()) {
            for (PropertyEditorRegistrar registrar : this.propertyEditorRegistrars) {
                try {
                    registrar.registerCustomEditors(registry);
                } catch (BeanCreationException ex) {
                    Throwable rootCause = ex.getMostSpecificCause();
                    if (rootCause instanceof BeanCurrentlyInCreationException) {
                        BeanCreationException bce = (BeanCreationException) rootCause;
                        if (isCurrentlyInCreation(bce.getBeanName())) {
                            if (logger.isDebugEnabled()) {
                                logger.debug("PropertyEditorRegistrar [" + registrar.getClass().getName() +
                                        "] failed because it tried to obtain currently created bean '" +
                                        ex.getBeanName() + "': " + ex.getMessage());
                            }
                            onSuppressedException(ex);
                            continue;
                        }
                    }
                    throw ex;
                }
            }
        }
        if (!this.customEditors.isEmpty()) {
            for (Map.Entry<Class<?>, Class<? extends PropertyEditor>> entry : this.customEditors.entrySet()) {
                Class<?> requiredType = entry.getKey();
                Class<? extends PropertyEditor> editorClass = entry.getValue();
                registry.registerCustomEditor(requiredType, BeanUtils.instantiateClass(editorClass));
            }
        }
    }


    /**
     * Return a merged RootBeanDefinition, traversing the parent bean definition
     * if the specified bean corresponds to a child bean definition.
     * 有缓存直接缓存取,没有的话就合并自己的和父类的.
     *
     * @param beanName the name of the bean to retrieve the merged definition for
     * @return a (potentially merged) RootBeanDefinition for the given bean
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @throws BeanDefinitionStoreException  in case of an invalid bean definition
     */
    protected RootBeanDefinition getMergedLocalBeanDefinition(String beanName) throws BeansException {
        // Quick check on the concurrent map first, with minimal locking.
        RootBeanDefinition mbd = this.mergedBeanDefinitions.get(beanName);
        if (mbd != null) {
            return mbd;
        }
        return getMergedBeanDefinition(beanName, getBeanDefinition(beanName));
    }

    /**
     * Return a RootBeanDefinition for the given top-level bean, by merging with
     * the parent if the given bean's definition is a child bean definition.
     *
     * @param beanName the name of the bean definition
     * @param bd       the original bean definition (Root/ChildBeanDefinition)
     * @return a (potentially merged) RootBeanDefinition for the given bean
     * @throws BeanDefinitionStoreException in case of an invalid bean definition
     */
    protected RootBeanDefinition getMergedBeanDefinition(String beanName, BeanDefinition bd)
            throws BeanDefinitionStoreException {

        return getMergedBeanDefinition(beanName, bd, null);
    }

    /**
     * Return a RootBeanDefinition for the given bean, by merging with the
     * parent if the given bean's definition is a child bean definition.
     *
     * @param beanName     the name of the bean definition
     * @param bd           the original bean definition (Root/ChildBeanDefinition)
     * @param containingBd the containing bean definition in case of inner bean,
     *                     or {@code null} in case of a top-level bean
     * @return a (potentially merged) RootBeanDefinition for the given bean
     * @throws BeanDefinitionStoreException in case of an invalid bean definition
     */
    protected RootBeanDefinition getMergedBeanDefinition(
            String beanName, BeanDefinition bd, BeanDefinition containingBd)
            throws BeanDefinitionStoreException {

        synchronized (this.mergedBeanDefinitions) {
            RootBeanDefinition mbd = null;

            // Check with full lock now in order to enforce the same merged instance.
            if (containingBd == null) {
                mbd = this.mergedBeanDefinitions.get(beanName);
            }

            if (mbd == null) {
                if (bd.getParentName() == null) {
                    // Use copy of given root bean definition.
                    if (bd instanceof RootBeanDefinition) {
                        mbd = ((RootBeanDefinition) bd).cloneBeanDefinition();
                    } else {
                        mbd = new RootBeanDefinition(bd);
                    }
                } else {
                    // Child bean definition: needs to be merged with parent.
                    BeanDefinition pbd;
                    try {
                        String parentBeanName = transformedBeanName(bd.getParentName());
                        if (!beanName.equals(parentBeanName)) {
                            pbd = getMergedBeanDefinition(parentBeanName);
                        } else {
                            if (getParentBeanFactory() instanceof ConfigurableBeanFactory) {
                                pbd = ((ConfigurableBeanFactory) getParentBeanFactory()).getMergedBeanDefinition(parentBeanName);
                            } else {
                                throw new NoSuchBeanDefinitionException(bd.getParentName(),
                                        "Parent name '" + bd.getParentName() + "' is equal to bean name '" + beanName +
                                                "': cannot be resolved without an AbstractBeanFactory parent");
                            }
                        }
                    } catch (NoSuchBeanDefinitionException ex) {
                        throw new BeanDefinitionStoreException(bd.getResourceDescription(), beanName,
                                "Could not resolve parent bean definition '" + bd.getParentName() + "'", ex);
                    }
                    // Deep copy with overridden values.
                    mbd = new RootBeanDefinition(pbd);
                    mbd.overrideFrom(bd);
                }

                // Set default singleton scope, if not configured before.
                if (!StringUtils.hasLength(mbd.getScope())) {
                    mbd.setScope(RootBeanDefinition.SCOPE_SINGLETON);
                }

                // A bean contained in a non-singleton bean cannot be a singleton itself.
                // Let's correct this on the fly here, since this might be the result of
                // parent-child merging for the outer bean, in which case the original inner bean
                // definition will not have inherited the merged outer bean's singleton status.
                if (containingBd != null && !containingBd.isSingleton() && mbd.isSingleton()) {
                    mbd.setScope(containingBd.getScope());
                }

                // Only cache the merged bean definition if we're already about to create an
                // instance of the bean, or at least have already created an instance before.
                if (containingBd == null && isCacheBeanMetadata() && isBeanEligibleForMetadataCaching(beanName)) {
                    this.mergedBeanDefinitions.put(beanName, mbd);
                }
            }

            return mbd;
        }
    }

    /**
     * Check the given merged bean definition,
     * potentially throwing validation exceptions.
     *
     * @param mbd      the merged bean definition to check
     * @param beanName the name of the bean
     * @param args     the arguments for bean creation, if any
     * @throws BeanDefinitionStoreException in case of validation failure
     */
    protected void checkMergedBeanDefinition(RootBeanDefinition mbd, String beanName, Object[] args)
            throws BeanDefinitionStoreException {

        if (mbd.isAbstract()) {
            throw new BeanIsAbstractException(beanName);
        }
    }

    /**
     * Remove the merged bean definition for the specified bean,
     * recreating it on next access.
     *
     * @param beanName the bean name to clear the merged definition for
     */
    protected void clearMergedBeanDefinition(String beanName) {
        this.mergedBeanDefinitions.remove(beanName);
    }

    /**
     * Resolve the bean class for the specified bean definition,
     * resolving a bean class name into a Class reference (if necessary)
     * and storing the resolved Class in the bean definition for further use.
     *
     * @param mbd          the merged bean definition to determine the class for
     * @param beanName     the name of the bean (for error handling purposes)
     * @param typesToMatch the types to match in case of internal type matching purposes
     *                     (also signals that the returned {@code Class} will never be exposed to application code)
     * @return the resolved bean class (or {@code null} if none)
     * @throws CannotLoadBeanClassException if we failed to load the class
     */
    protected Class<?> resolveBeanClass(final RootBeanDefinition mbd, String beanName, final Class<?>... typesToMatch)
            throws CannotLoadBeanClassException {
        try {
            if (mbd.hasBeanClass()) {
                return mbd.getBeanClass();
            }
            if (System.getSecurityManager() != null) {
                return AccessController.doPrivileged(new PrivilegedExceptionAction<Class<?>>() {
                    @Override
                    public Class<?> run() throws Exception {
                        return doResolveBeanClass(mbd, typesToMatch);
                    }
                }, getAccessControlContext());
            } else {
                return doResolveBeanClass(mbd, typesToMatch);
            }
        } catch (PrivilegedActionException pae) {
            ClassNotFoundException ex = (ClassNotFoundException) pae.getException();
            throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
        } catch (ClassNotFoundException ex) {
            throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
        } catch (LinkageError err) {
            throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), err);
        }
    }

    private Class<?> doResolveBeanClass(RootBeanDefinition mbd, Class<?>... typesToMatch) throws ClassNotFoundException {
        if (!ObjectUtils.isEmpty(typesToMatch)) {
            ClassLoader tempClassLoader = getTempClassLoader();
            if (tempClassLoader != null) {
                if (tempClassLoader instanceof DecoratingClassLoader) {
                    DecoratingClassLoader dcl = (DecoratingClassLoader) tempClassLoader;
                    for (Class<?> typeToMatch : typesToMatch) {
                        dcl.excludeClass(typeToMatch.getName());
                    }
                }
                String className = mbd.getBeanClassName();
                return (className != null ? ClassUtils.forName(className, tempClassLoader) : null);
            }
        }
        return mbd.resolveBeanClass(getBeanClassLoader());
    }

    /**
     * Evaluate the given String as contained in a bean definition,
     * potentially resolving it as an expression.
     *
     * @param value          the value to check
     * @param beanDefinition the bean definition that the value comes from
     * @return the resolved value
     * @see #setBeanExpressionResolver
     */
    protected Object evaluateBeanDefinitionString(String value, BeanDefinition beanDefinition) {
        if (this.beanExpressionResolver == null) {
            return value;
        }
        Scope scope = (beanDefinition != null ? getRegisteredScope(beanDefinition.getScope()) : null);
        return this.beanExpressionResolver.evaluate(value, new BeanExpressionContext(this, scope));
    }


    /**
     * Predict the eventual bean type (of the processed bean instance) for the
     * specified bean. Called by {@link #getType} and {@link #isTypeMatch}.
     * Does not need to handle FactoryBeans specifically, since it is only
     * supposed to operate on the raw bean type.
     * <p>This implementation is simplistic in that it is not able to
     * handle factory methods and InstantiationAwareBeanPostProcessors.
     * It only predicts the bean type correctly for a standard bean.
     * To be overridden in subclasses, applying more sophisticated type detection.
     *
     * @param beanName     the name of the bean
     * @param mbd          the merged bean definition to determine the type for
     * @param typesToMatch the types to match in case of internal type matching purposes
     *                     (also signals that the returned {@code Class} will never be exposed to application code)
     * @return the type of the bean, or {@code null} if not predictable
     */
    protected Class<?> predictBeanType(String beanName, RootBeanDefinition mbd, Class<?>... typesToMatch) {
        if (mbd.getFactoryMethodName() != null) {
            return null;
        }
        return resolveBeanClass(mbd, beanName, typesToMatch);
    }

    /**
     * Check whether the given bean is defined as a {@link FactoryBean}.
     *
     * @param beanName the name of the bean
     * @param mbd      the corresponding bean definition
     */
    protected boolean isFactoryBean(String beanName, RootBeanDefinition mbd) {
        Class<?> beanType = predictBeanType(beanName, mbd, FactoryBean.class);
        return (beanType != null && FactoryBean.class.isAssignableFrom(beanType));
    }

    /**
     * Determine the bean type for the given FactoryBean definition, as far as possible.
     * Only called if there is no singleton instance registered for the target bean already.
     * <p>The default implementation creates the FactoryBean via {@code getBean}
     * to call its {@code getObjectType} method. Subclasses are encouraged to optimize
     * this, typically by just instantiating the FactoryBean but not populating it yet,
     * trying whether its {@code getObjectType} method already returns a type.
     * If no type found, a full FactoryBean creation as performed by this implementation
     * should be used as fallback.
     *
     * @param beanName the name of the bean
     * @param mbd      the merged bean definition for the bean
     * @return the type for the bean if determinable, or {@code null} else
     * @see org.springframework.beans.factory.FactoryBean#getObjectType()
     * @see #getBean(String)
     */
    protected Class<?> getTypeForFactoryBean(String beanName, RootBeanDefinition mbd) {
        if (!mbd.isSingleton()) {
            return null;
        }
        try {
            FactoryBean<?> factoryBean = doGetBean(FACTORY_BEAN_PREFIX + beanName, FactoryBean.class, null, true);
            return getTypeForFactoryBean(factoryBean);
        } catch (BeanCreationException ex) {
            if (ex instanceof BeanCurrentlyInCreationException) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Bean currently in creation on FactoryBean type check: " + ex);
                }
            } else {
                if (logger.isWarnEnabled()) {
                    logger.warn("Bean creation exception on FactoryBean type check: " + ex);
                }
            }
            onSuppressedException(ex);
            return null;
        }
    }

    /**
     * Mark the specified bean as already created (or about to be created).
     * <p>This allows the bean factory to optimize its caching for repeated
     * creation of the specified bean.
     *
     * @param beanName the name of the bean
     */
    protected void markBeanAsCreated(String beanName) {
        if (!this.alreadyCreated.contains(beanName)) {
            this.alreadyCreated.add(beanName);
        }
    }

    /**
     * Perform appropriate cleanup of cached metadata after bean creation failed.
     *
     * @param beanName the name of the bean
     */
    protected void cleanupAfterBeanCreationFailure(String beanName) {
        this.alreadyCreated.remove(beanName);
    }

    /**
     * Determine whether the specified bean is eligible for having
     * its bean definition metadata cached.
     *
     * @param beanName the name of the bean
     * @return {@code true} if the bean's metadata may be cached
     * at this point already
     */
    protected boolean isBeanEligibleForMetadataCaching(String beanName) {
        return this.alreadyCreated.contains(beanName);
    }

    /**
     * Remove the singleton instance (if any) for the given bean name,
     * but only if it hasn't been used for other purposes than type checking.
     *
     * @param beanName the name of the bean
     * @return {@code true} if actually removed, {@code false} otherwise
     */
    protected boolean removeSingletonIfCreatedForTypeCheckOnly(String beanName) {
        if (!this.alreadyCreated.contains(beanName)) {
            removeSingleton(beanName);
            return true;
        } else {
            return false;
        }
    }

    /**
     * Get the object for the given bean instance, either the bean
     * instance itself or its created object in case of a FactoryBean.
     *
     * @param beanInstance the shared bean instance
     * @param name         name that may include factory dereference prefix
     * @param beanName     the canonical bean name
     * @param mbd          the merged bean definition
     * @return the object to expose for the bean
     */
    protected Object getObjectForBeanInstance(
            Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {

        // Don't let calling code try to dereference the factory if the bean isn't a factory.
        // & 开头.但是这个bean却又不是FactoryBean.说明有问题. &都应该是factorybean
        if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
            throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
        }

        // Now we have the bean instance, which may be a normal bean or a FactoryBean.
        // If it's a FactoryBean, we use it to create a bean instance, unless the
        // caller actually wants a reference to the factory.
        // 不是FactoryBean直接返回这个bean,&开头的话也直接返回这个bean.
        if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
            return beanInstance;
        }

        Object object = null;
        if (mbd == null) {
            // 说明这个bean是需要从FactoryBean的getObject方法中返回的.
            object = getCachedObjectForFactoryBean(beanName);
        }
        if (object == null) { // 没有cache.需要生成的情况
            // Return bean instance from factory.
            FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
            // Caches object obtained from FactoryBean if it is a singleton.
            if (mbd == null && containsBeanDefinition(beanName)) {
                mbd = getMergedLocalBeanDefinition(beanName); // 合并bean的定义
            }
            boolean synthetic = (mbd != null && mbd.isSynthetic());
            object = getObjectFromFactoryBean(factory, beanName, !synthetic); // 不是合成的bean的定义的话这个bean从工厂中生成需要调用postProcessObjectFromFactoryBean方法对bean进行加工,我觉得是因为父类中的这些后置处理bean当前工厂里没有
        }
        return object;
    }

    /**
     * Determine whether the given bean name is already in use within this factory,
     * i.e. whether there is a local bean or alias registered under this name or
     * an inner bean created with this name.
     *
     * @param beanName the name to check
     */
    public boolean isBeanNameInUse(String beanName) {
        return isAlias(beanName) || containsLocalBean(beanName) || hasDependentBean(beanName);
    }

    /**
     * Determine whether the given bean requires destruction on shutdown.
     * <p>The default implementation checks the DisposableBean interface as well as
     * a specified destroy method and registered DestructionAwareBeanPostProcessors.
     *
     * @param bean the bean instance to check
     * @param mbd  the corresponding bean definition
     * @see org.springframework.beans.factory.DisposableBean
     * @see AbstractBeanDefinition#getDestroyMethodName()
     * @see org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor
     */
    protected boolean requiresDestruction(Object bean, RootBeanDefinition mbd) {
        return (bean != null &&
                (DisposableBeanAdapter.hasDestroyMethod(bean, mbd) || hasDestructionAwareBeanPostProcessors()));
    }

    /**
     * Add the given bean to the list of disposable beans in this factory,
     * registering its DisposableBean interface and/or the given destroy method
     * to be called on factory shutdown (if applicable). Only applies to singletons.
     *
     * @param beanName the name of the bean
     * @param bean     the bean instance
     * @param mbd      the bean definition for the bean
     * @see RootBeanDefinition#isSingleton
     * @see RootBeanDefinition#getDependsOn
     * @see #registerDisposableBean
     * @see #registerDependentBean
     */
    protected void registerDisposableBeanIfNecessary(String beanName, Object bean, RootBeanDefinition mbd) {
        AccessControlContext acc = (System.getSecurityManager() != null ? getAccessControlContext() : null);
        if (!mbd.isPrototype() && requiresDestruction(bean, mbd)) {
            if (mbd.isSingleton()) {
                // Register a DisposableBean implementation that performs all destruction
                // work for the given bean: DestructionAwareBeanPostProcessors,
                // DisposableBean interface, custom destroy method.
                registerDisposableBean(beanName,
                        new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
            } else {
                // A bean with a custom scope...
                Scope scope = this.scopes.get(mbd.getScope());
                if (scope == null) {
                    throw new IllegalStateException("No Scope registered for scope '" + mbd.getScope() + "'");
                }
                scope.registerDestructionCallback(beanName,
                        new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
            }
        }
    }


    //---------------------------------------------------------------------
    // Abstract methods to be implemented by subclasses
    //---------------------------------------------------------------------

    /**
     * Check if this bean factory contains a bean definition with the given name.
     * Does not consider any hierarchy this factory may participate in.
     * Invoked by {@code containsBean} when no cached singleton instance is found.
     * <p>Depending on the nature of the concrete bean factory implementation,
     * this operation might be expensive (for example, because of directory lookups
     * in external registries). However, for listable bean factories, this usually
     * just amounts to a local hash lookup: The operation is therefore part of the
     * public interface there. The same implementation can serve for both this
     * template method and the public interface method in that case.
     * 当前这个BF不算父类的.是否包含了给定的beanname对应的Definition
     *
     * @param beanName the name of the bean to look for
     * @return if this bean factory contains a bean definition with the given name
     * @see #containsBean
     * @see org.springframework.beans.factory.ListableBeanFactory#containsBeanDefinition
     */
    protected abstract boolean containsBeanDefinition(String beanName);

    /**
     * Return the bean definition for the given bean name.
     * Subclasses should normally implement caching, as this method is invoked
     * by this class every time bean definition metadata is needed.
     * <p>Depending on the nature of the concrete bean factory implementation,
     * this operation might be expensive (for example, because of directory lookups
     * in external registries). However, for listable bean factories, this usually
     * just amounts to a local hash lookup: The operation is therefore part of the
     * public interface there. The same implementation can serve for both this
     * template method and the public interface method in that case.
     * 根据beanname获取BeanDefinition,子类实现,可以用缓存
     *
     * @param beanName the name of the bean to find a definition for
     * @return the BeanDefinition for this prototype name (never {@code null})
     * @throws org.springframework.beans.factory.NoSuchBeanDefinitionException if the bean definition cannot be resolved
     * @throws BeansException                                                  in case of errors
     * @see RootBeanDefinition
     * @see ChildBeanDefinition
     * @see org.springframework.beans.factory.config.ConfigurableListableBeanFactory#getBeanDefinition
     */
    protected abstract BeanDefinition getBeanDefinition(String beanName) throws BeansException;

    /**
     * Create a bean instance for the given merged bean definition (and arguments).
     * The bean definition will already have been merged with the parent definition
     * in case of a child definition.
     * <p>All bean retrieval methods delegate to this method for actual bean creation.
     *
     * @param beanName the name of the bean
     * @param mbd      the merged bean definition for the bean
     * @param args     explicit arguments to use for constructor or factory method invocation
     * @return a new instance of the bean
     * @throws BeanCreationException if the bean could not be created
     */
    protected abstract Object createBean(String beanName, RootBeanDefinition mbd, Object[] args)
            throws BeanCreationException;

}

一些方法加了注释,还有很多方法和其中的ifelse不明白为什么要这么写...

后续的一些逻辑要做实验才会明白了....