Spring学习之IOC容器1

　　在Spring IOC容器的设计中，有两个主要的容器系列，一个是实现BeanFactory接口的简单容器系列，这系列容器只实现了容器的最基本功能；另一个是ApplicationContext应用上下文，它作为容器的高级形态而存在。应用上下文在简单容器的基础上，增加了许多面向框架的特性，同时对应用环境做了许多适配。

　　用户在使用容器时，可以使用转义符“&”来得到FactoryBean本身，用来区分通过容器来获得FactoryBean产生的对象和获取FactoryBean本身。例如，如果MyBean是一个FactoryBean，那么使用&MyBean得到的是FactoryBean，而不是MyBean这个FactoryBean产生出来的对象。

　　BeanFactory接口设计了getBean()方法，通过这个方法可以得到IOC容器中管理的bean，bean的去的是通过指定名字来索引的。

　　用户可以执行以下操作：

　　1.通过接口方法constainsBean让用户能够判断容器事都含有指定名字的Bean。

　　2.通过接口方法isSingleton来查询指定名字的Bean是否是Singleton类型的Bean。对于Singleton属性，用户可以在BeanDefinition中指定。

　　3.通过接口方法isPrototype来查询指定名字的Bean是否是prototype类型的。与Singleton属性是一样的，这个属性也可以由用户在BeanDefinition中指定。

　　4.通过接口方法isTypeMatch来查询指定了名字的Bean的Class类型是否是特定的Class类型。这个Class类型可以由用户来指定。

　　5.通过接口方法getType来查询指定名字的Bean的Class类型。

　　6.通过接口方法getAliases来查询指定了名字的Bean的所有别名，这些别名都是由用户在Beandefinition中定义的。

　　

/*
 * Copyright 2002-2013 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;

import org.springframework.beans.BeansException;

/**
 * The root interface for accessing a Spring bean container.
 * This is the basic client view of a bean container;
 * further interfaces such as {@link ListableBeanFactory} and
 * {@link org.springframework.beans.factory.config.ConfigurableBeanFactory}
 * are available for specific purposes.
 *
 * <p>This interface is implemented by objects that hold a number of bean definitions,
 * each uniquely identified by a String name. Depending on the bean definition,
 * the factory will return either an independent instance of a contained object
 * (the Prototype design pattern), or a single shared instance (a superior
 * alternative to the Singleton design pattern, in which the instance is a
 * singleton in the scope of the factory). Which type of instance will be returned
 * depends on the bean factory configuration: the API is the same. Since Spring
 * 2.0, further scopes are available depending on the concrete application
 * context (e.g. "request" and "session" scopes in a web environment).
 *
 * <p>The point of this approach is that the BeanFactory is a central registry
 * of application components, and centralizes configuration of application
 * components (no more do individual objects need to read properties files,
 * for example). See chapters 4 and 11 of "Expert One-on-One J2EE Design and
 * Development" for a discussion of the benefits of this approach.
 *
 * <p>Note that it is generally better to rely on Dependency Injection
 * ("push" configuration) to configure application objects through setters
 * or constructors, rather than use any form of "pull" configuration like a
 * BeanFactory lookup. Spring's Dependency Injection functionality is
 * implemented using this BeanFactory interface and its subinterfaces.
 *
 * <p>Normally a BeanFactory will load bean definitions stored in a configuration
 * source (such as an XML document), and use the {@code org.springframework.beans}
 * package to configure the beans. However, an implementation could simply return
 * Java objects it creates as necessary directly in Java code. There are no
 * constraints on how the definitions could be stored: LDAP, RDBMS, XML,
 * properties file, etc. Implementations are encouraged to support references
 * amongst beans (Dependency Injection).
 *
 * <p>In contrast to the methods in {@link ListableBeanFactory}, all of the
 * operations in this interface will also check parent factories if this is a
 * {@link HierarchicalBeanFactory}. If a bean is not found in this factory instance,
 * the immediate parent factory will be asked. Beans in this factory instance
 * are supposed to override beans of the same name in any parent factory.
 *
 * <p>Bean factory implementations should support the standard bean lifecycle interfaces
 * as far as possible. The full set of initialization methods and their standard order is:<br>
 * 1. BeanNameAware's {@code setBeanName}<br>
 * 2. BeanClassLoaderAware's {@code setBeanClassLoader}<br>
 * 3. BeanFactoryAware's {@code setBeanFactory}<br>
 * 4. ResourceLoaderAware's {@code setResourceLoader}
 * (only applicable when running in an application context)<br>
 * 5. ApplicationEventPublisherAware's {@code setApplicationEventPublisher}
 * (only applicable when running in an application context)<br>
 * 6. MessageSourceAware's {@code setMessageSource}
 * (only applicable when running in an application context)<br>
 * 7. ApplicationContextAware's {@code setApplicationContext}
 * (only applicable when running in an application context)<br>
 * 8. ServletContextAware's {@code setServletContext}
 * (only applicable when running in a web application context)<br>
 * 9. {@code postProcessBeforeInitialization} methods of BeanPostProcessors<br>
 * 10. InitializingBean's {@code afterPropertiesSet}<br>
 * 11. a custom init-method definition<br>
 * 12. {@code postProcessAfterInitialization} methods of BeanPostProcessors
 *
 * <p>On shutdown of a bean factory, the following lifecycle methods apply:<br>
 * 1. DisposableBean's {@code destroy}<br>
 * 2. a custom destroy-method definition
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Chris Beams
 * @since 13 April 2001
 * @see BeanNameAware#setBeanName
 * @see BeanClassLoaderAware#setBeanClassLoader
 * @see BeanFactoryAware#setBeanFactory
 * @see org.springframework.context.ResourceLoaderAware#setResourceLoader
 * @see org.springframework.context.ApplicationEventPublisherAware#setApplicationEventPublisher
 * @see org.springframework.context.MessageSourceAware#setMessageSource
 * @see org.springframework.context.ApplicationContextAware#setApplicationContext
 * @see org.springframework.web.context.ServletContextAware#setServletContext
 * @see org.springframework.beans.factory.config.BeanPostProcessor#postProcessBeforeInitialization
 * @see InitializingBean#afterPropertiesSet
 * @see org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName
 * @see org.springframework.beans.factory.config.BeanPostProcessor#postProcessAfterInitialization
 * @see DisposableBean#destroy
 * @see org.springframework.beans.factory.support.RootBeanDefinition#getDestroyMethodName
 */
public interface BeanFactory {

    /**
     * Used to dereference a {@link FactoryBean} instance and distinguish it from
     * beans <i>created</i> by the FactoryBean. For example, if the bean named
     * {@code myJndiObject} is a FactoryBean, getting {@code &myJndiObject}
     * will return the factory, not the instance returned by the factory.
     */
    String FACTORY_BEAN_PREFIX = "&";

    /**
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>This method allows a Spring BeanFactory to be used as a replacement for the
     * Singleton or Prototype design pattern. Callers may retain references to
     * returned objects in the case of Singleton beans.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to retrieve
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no bean definition
     * with the specified name
     * @throws BeansException if the bean could not be obtained
     */
    Object getBean(String name) throws BeansException;

    /**
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>Behaves the same as {@link #getBean(String)}, but provides a measure of type
     * safety by throwing a BeanNotOfRequiredTypeException if the bean is not of the
     * required type. This means that ClassCastException can't be thrown on casting
     * the result correctly, as can happen with {@link #getBean(String)}.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to retrieve
     * @param requiredType type the bean must match. Can be an interface or superclass
     * of the actual class, or {@code null} for any match. For example, if the value
     * is {@code Object.class}, this method will succeed whatever the class of the
     * returned instance.
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no such bean definition
     * @throws BeanNotOfRequiredTypeException if the bean is not of the required type
     * @throws BeansException if the bean could not be created
     */
    <T> T getBean(String name, Class<T> requiredType) throws BeansException;

    /**
     * Return the bean instance that uniquely matches the given object type, if any.
     * @param requiredType type the bean must match; can be an interface or superclass.
     * {@code null} is disallowed.
     * <p>This method goes into {@link ListableBeanFactory} by-type lookup territory
     * but may also be translated into a conventional by-name lookup based on the name
     * of the given type. For more extensive retrieval operations across sets of beans,
     * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.
     * @return an instance of the single bean matching the required type
     * @throws NoSuchBeanDefinitionException if no bean of the given type was found
     * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found
     * @since 3.0
     * @see ListableBeanFactory
     */
    <T> T getBean(Class<T> requiredType) throws BeansException;

    /**
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>Allows for specifying explicit constructor arguments / factory method arguments,
     * overriding the specified default arguments (if any) in the bean definition.
     * @param name the name of the bean to retrieve
     * @param args arguments to use if creating a prototype using explicit arguments to a
     * static factory method. It is invalid to use a non-null args value in any other case.
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no such bean definition
     * @throws BeanDefinitionStoreException if arguments have been given but
     * the affected bean isn't a prototype
     * @throws BeansException if the bean could not be created
     * @since 2.5
     */
    Object getBean(String name, Object... args) throws BeansException;

    /**
     * Does this bean factory contain a bean definition or externally registered singleton
     * instance with the given name?
     * <p>If the given name is an alias, it will be translated back to the corresponding
     * canonical bean name.
     * <p>If this factory is hierarchical, will ask any parent factory if the bean cannot
     * be found in this factory instance.
     * <p>If a bean definition or singleton instance matching the given name is found,
     * this method will return {@code true} whether the named bean definition is concrete
     * or abstract, lazy or eager, in scope or not. Therefore, note that a {@code true}
     * return value from this method does not necessarily indicate that {@link #getBean}
     * will be able to obtain an instance for the same name.
     * @param name the name of the bean to query
     * @return whether a bean with the given name is present
     */
    boolean containsBean(String name);

    /**
     * Is this bean a shared singleton? That is, will {@link #getBean} always
     * return the same instance?
     * <p>Note: This method returning {@code false} does not clearly indicate
     * independent instances. It indicates non-singleton instances, which may correspond
     * to a scoped bean as well. Use the {@link #isPrototype} operation to explicitly
     * check for independent instances.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @return whether this bean corresponds to a singleton instance
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @see #getBean
     * @see #isPrototype
     */
    boolean isSingleton(String name) throws NoSuchBeanDefinitionException;

    /**
     * Is this bean a prototype? That is, will {@link #getBean} always return
     * independent instances?
     * <p>Note: This method returning {@code false} does not clearly indicate
     * a singleton object. It indicates non-independent instances, which may correspond
     * to a scoped bean as well. Use the {@link #isSingleton} operation to explicitly
     * check for a shared singleton instance.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @return whether this bean will always deliver independent instances
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 2.0.3
     * @see #getBean
     * @see #isSingleton
     */
    boolean isPrototype(String name) throws NoSuchBeanDefinitionException;

    /**
     * Check whether the bean with the given name matches the specified type.
     * More specifically, check whether a {@link #getBean} call for the given name
     * would return an object that is assignable to the specified target type.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @param targetType the type to match against
     * @return {@code true} if the bean type matches,
     * {@code false} if it doesn't match or cannot be determined yet
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 2.0.1
     * @see #getBean
     * @see #getType
     */
    boolean isTypeMatch(String name, Class<?> targetType) throws NoSuchBeanDefinitionException;

    /**
     * Determine the type of the bean with the given name. More specifically,
     * determine the type of object that {@link #getBean} would return for the given name.
     * <p>For a {@link FactoryBean}, return the type of object that the FactoryBean creates,
     * as exposed by {@link FactoryBean#getObjectType()}.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @return the type of the bean, or {@code null} if not determinable
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 1.1.2
     * @see #getBean
     * @see #isTypeMatch
     */
    Class<?> getType(String name) throws NoSuchBeanDefinitionException;

    /**
     * Return the aliases for the given bean name, if any.
     * All of those aliases point to the same bean when used in a {@link #getBean} call.
     * <p>If the given name is an alias, the corresponding original bean name
     * and other aliases (if any) will be returned, with the original bean name
     * being the first element in the array.
     * <p>Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the bean name to check for aliases
     * @return the aliases, or an empty array if none
     * @see #getBean
     */
    String[] getAliases(String name);

}