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  • Spring 学习记录8 初识XmlWebApplicationContext(2)

    主题

    接上文Spring 学习记录7 初识XmlWebApplicationContext

    refresh方法

    refresh方法是定义在父类AbstractApplicationContext中的.它内部会调用很多方法.有一些是在子类中实现的.算是模板方法的设计模式吧.主要作用就是初始化wac加载各种bean等作用.

     1 @Override
 2     public void refresh() throws BeansException, IllegalStateException {
 3         synchronized (this.startupShutdownMonitor) {
 4             // Prepare this context for refreshing.
 5             // 记录开始wac开始初始化的时间,设置激活标记,servlet的相关param设置到env(之前做过1次),校验env中必须的props
 6             prepareRefresh();
 7 
 8             // Tell the subclass to refresh the internal bean factory.
 9             // 刷新初始化BF并获取它,将旧的BF里的bean删掉,新建1个BF,加载XML配置文件
10             ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
11 
12             // Prepare the bean factory for use in this context.
13             prepareBeanFactory(beanFactory);
14 
15             try {
16                 // Allows post-processing of the bean factory in context subclasses.
17                 postProcessBeanFactory(beanFactory);
18 
19                 // Invoke factory processors registered as beans in the context.
20                 invokeBeanFactoryPostProcessors(beanFactory);
21 
22                 // Register bean processors that intercept bean creation.
23                 registerBeanPostProcessors(beanFactory);
24 
25                 // Initialize message source for this context.
26                 initMessageSource();
27 
28                 // Initialize event multicaster for this context.
29                 initApplicationEventMulticaster();
30 
31                 // Initialize other special beans in specific context subclasses.
32                 onRefresh();
33 
34                 // Check for listener beans and register them.
35                 registerListeners();
36 
37                 // Instantiate all remaining (non-lazy-init) singletons.
38                 finishBeanFactoryInitialization(beanFactory);
39 
40                 // Last step: publish corresponding event.
41                 finishRefresh();
42             } catch (BeansException ex) {
43                 logger.warn("Exception encountered during context initialization - cancelling refresh attempt", ex);
44 
45                 // Destroy already created singletons to avoid dangling resources.
46                 destroyBeans();
47 
48                 // Reset 'active' flag.
49                 cancelRefresh(ex);
50 
51                 // Propagate exception to caller.
52                 throw ex;
53             }
54         }
55     }
    View Code

    prepareRefresh方法

    第一个被调用的方法就是它

    主要作用:

    记录开始wac开始初始化的时间,设置激活标记,servlet的相关param设置到env(之前做过1次),校验env中必须的props

     1     /**
 2      * Prepare this context for refreshing, setting its startup date and
 3      * active flag as well as performing any initialization of property sources.
 4      * 记录开始wac开始初始化的时间,设置激活标记,servlet的相关param设置到env(之前做过1次),校验env中必须的props
 5      */
 6     protected void prepareRefresh() {
 7         this.startupDate = System.currentTimeMillis();
 8         this.active.set(true);
 9 
10         if (logger.isInfoEnabled()) {
11             logger.info("Refreshing " + this);
12         }
13 
14         // Initialize any placeholder property sources in the context environment
15         // 讲servlet的config和context里的params赋值给env..之前已经做过一次了,这个wac可能会由servlet初始化,这样的话ServletConfig就不会为空
16         initPropertySources();
17 
18         // Validate that all properties marked as required are resolvable
19         // see ConfigurablePropertyResolver#setRequiredProperties
20         // 在env中有一些properties是必须的,校验这些props.没有就抛出异常
21         getEnvironment().validateRequiredProperties();
22     }

    L16..这个方法做了什么直接看注释吧..

     1     /**
 2      * {@inheritDoc}
 3      * <p>Replace {@code Servlet}-related property sources.
 4      */
 5     @Override
 6     protected void initPropertySources() {
 7         ConfigurableEnvironment env = getEnvironment();
 8         if (env instanceof ConfigurableWebEnvironment) {
 9             ((ConfigurableWebEnvironment) env).initPropertySources(this.servletContext, this.servletConfig);
10         }
11     }

    就是拿servletContext和servletConfig去填充env....和之前做的一样....如果是listener初始化的话这里servletConfig肯定是空的.

    L21 对env里的必须的属性进行校验.如果这些属性不存在的话就报错.(但是我源码里搜索了一下并没有找到调用设置必须属性的地方...不知道怎么使用才能标记属性为必须....)

    obtainFreshBeanFactory方法

    主要作用:

    刷新初始化BF并获取它,将旧的BF里的bean删掉,新建1个BF,加载XML配置文件

     1     /**
 2      * Tell the subclass to refresh the internal bean factory.
 3      * 刷新初始化BF并获取它,将旧的BF里的bean删掉,新建1个BF,加载XML配置文件
 4      *
 5      * @return the fresh BeanFactory instance
 6      * @see #refreshBeanFactory()
 7      * @see #getBeanFactory()
 8      */
 9     protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
10         refreshBeanFactory(); // 刷新BF
11         ConfigurableListableBeanFactory beanFactory = getBeanFactory();
12         if (logger.isDebugEnabled()) {
13             logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
14         }
15         return beanFactory;
16     }

    L10 refreshBeanFactory(); 

     1     /**
 2      * This implementation performs an actual refresh of this context's underlying
 3      * bean factory, shutting down the previous bean factory (if any) and
 4      * initializing a fresh bean factory for the next phase of the context's lifecycle.
 5      */
 6     @Override
 7     protected final void refreshBeanFactory() throws BeansException {
 8         if (hasBeanFactory()) {
 9             destroyBeans(); // 删除所有单例bean
10             closeBeanFactory(); // wac中的BF成员域=null.
11         }
12         try {
13             DefaultListableBeanFactory beanFactory = createBeanFactory(); // 创建1个新的DefaultListableBeanFactory
14             beanFactory.setSerializationId(getId()); // 设置ID
15             customizeBeanFactory(beanFactory); // wac 中的属性 allowBeanDefinitionOverriding allowCircularReferences 覆盖BF
16             loadBeanDefinitions(beanFactory); // 加载BeanDefinitions.
17             synchronized (this.beanFactoryMonitor) {
18                 this.beanFactory = beanFactory;
19             }
20         } catch (IOException ex) {
21             throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
22         }
23     }
    View Code

    主要作用就是先把之前的beanfactory里创建的bean都销毁,然后销毁beanfactory.

    然后新建1个DefaultListableBeanFactory,并配置一些通过wac配置的属性.

    再加载一下bean的配置.在这里因为wac是XmlWebApplicationContext,所以bean的配置肯定是写在XML里的了.

    最后把bf对象设置到wac的成员域上.

    L11得到之前设置的新的BF并在L15返回...

    prepareBeanFactory方法

    主要作用:

    1.设置BF解析bean配置需要用到的一些对象比如env. 2.注册一些BeanPostProcessor比如ApplicationContextAwareProcessor去设置Aware需要的对象 3.忽略一些特定class注入的对象,设置一些特定class注入的对象为指定值 4.将一些env中的properties map当做bean注册到BF中

     1 /**
 2      * Configure the factory's standard context characteristics,
 3      * such as the context's ClassLoader and post-processors.
 4      *
 5      * @param beanFactory the BeanFactory to configure
 6      */
 7     protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
 8         // Tell the internal bean factory to use the context's class loader etc.
 9         // BF需要解析属性或者转化需要用到env和其他相关的类.从wac中设置进去
10         beanFactory.setBeanClassLoader(getClassLoader());
11         beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
12         beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
13 
14         // Configure the bean factory with context callbacks.
15         // 因为bean是在BF中创建的,所以如果他们需要用到wac的callback比如ApplicationEventPublisherAware的方法或者ApplicationContextAware,
16         // 那就需要再BF生成bean的时候注入applicationcontext或者它的相关类.比如env
17         beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
18         beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
19         beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
20         beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
21         beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
22         beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
23 
24         // BeanFactory interface not registered as resolvable type in a plain factory.
25         // MessageSource registered (and found for autowiring) as a bean.
26         // 如果要注入以下类型的bean,直接使用这些对象
27         beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
28         beanFactory.registerResolvableDependency(ResourceLoader.class, this);
29         beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
30         beanFactory.registerResolvableDependency(ApplicationContext.class, this);
31 
32         // Detect a LoadTimeWeaver and prepare for weaving, if found.
33         if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
34             beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
35             // Set a temporary ClassLoader for type matching.
36             beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
37         }
38 
39         // Register default environment beans.
40         // 将一些properties当做bean放到BF中
41         if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
42             beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
43         }
44         if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
45             beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
46         }
47         if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
48             beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
49         }
50     }

    第一个代码块就是设置一些BF解析bean需要用到的对象.比如env.

    第二个代码块就是add了一些XXXAwareProcess.比如applicationContextAware...BF在创建这个bean以后会调用ApplicationContextAwareProcessor的回调函数去注入applicationContext.

    然后忽略了一些接口,他们不会被注入实现类.

    第三个代码块配置了一些接口的注入的实现类.

    第四个代码又注入了一个BeanPostProcessor,这个似乎和AOP有关系.没研究过.

    第五个代码块就是把env中的一些props当做bean注册到BF中去.

    postProcessBeanFactory方法

    又是1个模板方法.可以对BF进行一些加工定制.

    在web环境下有重写过.

    主要作用:

    1.设置一个BeanPostProcess为ServletContextAware的实现类注入servlet相关对象
    2.在BF中增加requetsScope等Scope
    3.把servletContext,Config,ServletInitParams,ServletAttribute当做Bean注册到BF中
     1     /**
 2      * Register request/session scopes, a {@link ServletContextAwareProcessor}, etc.
 3      * 1.设置一个BeanPostProcess为ServletContextAware的实现类注入servlet相关对象
 4      * 2.在BF中增加requetsScope等Scope
 5      * 3.把servletContext,Config,ServletInitParams,ServletAttribute当做Bean注册到BF中
 6      *
 7      */
 8     @Override
 9     protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
10         // 设置一个BeanPostProcess为ServletContextAware的实现类注入servlet相关对象
11         beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));
12         beanFactory.ignoreDependencyInterface(ServletContextAware.class);
13         beanFactory.ignoreDependencyInterface(ServletConfigAware.class);
14 
15         // 在BF中增加requetsScope等Scope
16         WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);
17         // 把servletContext,Config,ServletInitParams,ServletAttribute当做Bean注册到BF中
18         WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);
19     }

    invokeBeanFactoryPostProcessors方法

    初始化并调用配置的BeanFactoryPostProcessor..具体比较复杂.等后续更多学习以后再分享.

    registerBeanPostProcessors方法

    基本同invokeBeanFactoryPostProcessors方法,这是这里不会调用BeanPostProcess只是向BF里注册而已.具体比较复杂.等后续更多学习以后再分享.
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  • 原文地址：https://www.cnblogs.com/abcwt112/p/7755066.html
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