spring系列之IOC容器实例化过程四

fresh中的prepareBeanFactory方法

很好，过年期间订下的计划没有完成，我知道我有罪，但是过年这段期间是真的好好玩！！。我觉得好好玩个几天应该也不过分，哈哈哈！！最后希望看到这篇博客的小伙伴可以点点赞，编写不易。

prepareBeanFactory方法负责对BeanFactory进行一些特征的设置工作，"特征"包含这么几个方面:

BeanexpressionResolverPropertyEditorRegistrar环境注入依赖解析忽略bean伪装LoadTimeWeaver注册环境

在讲解这几个方面之前还是先贴上方法的代码：

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {// Tell the internal bean factory to use the context's class loader etc.beanFactory.setBeanClassLoader(getClassLoader());beanFactory.setBeanexpressionResolver(new StandardBeanexpressionResolver(beanFactory.getBeanClassLoader()));beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));// Configure the bean factory with context callbacks.beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));beanFactory.ignoreDependencyInterface(EnvironmentAware.class);beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);beanFactory.ignoreDependencyInterface(MessageSourceAware.class);beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);// BeanFactory interface not registered as resolvable type in a plain factory.// MessageSource registered (and found for autowiring) as a bean.beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);beanFactory.registerResolvableDependency(ResourceLoader.class, this);beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);beanFactory.registerResolvableDependency(ApplicationContext.class, this);// Register early post-processor for detecting inner beans as ApplicationListeners.beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));// Detect a LoadTimeWeaver and prepare for weaving, if found.if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));// Set a temporary ClassLoader for type matching.beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));}// Register default environment beans.if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());}if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());}if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());}}

1.BeanexpressionResolver

此接口只有一个实现: StandardBeanexpressionResolver。接口只含有一个方法:

Object evaluate(String value, BeanexpressionContext evalContext) throws BeansException;

prepareBeanFactory将一个此对象放入BeanFactory:

beanFactory.setBeanexpressionResolver(new StandardBeanexpressionResolver(beanFactory.getBeanClassLoader()));

StandardBeanexpressionResolver对象内部有一个关键的成员: SpelexpressionParser，它的存在支撑着Spring3.0开始出现的Spel表达式功能。

2.PropertyEditorRegistrar

此接口用于向Spring注册java.beans.PropertyEditor，只有一个方法:

void addPropertyEditorRegistrar(PropertyEditorRegistrar registrar);

实现也只有一个: ResourceEditorRegistrar。

在编写xml配置时，我们设置的值都是字符串形式，所以在使用时肯定需要转为我们需要的类型，PropertyEditor接口正是定义了这么个东西。

beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

BeanFactory也暴露了registerCustomEditors方法用以添加自定义的转换器，所以这个地方是组合模式的体现。

我们有两种方式可以添加自定义PropertyEditor:

通过context.getBeanFactory().registerCustomEditor通过Spring配置文件:

3.环境注入

在Spring中我们自己的bean可以通过实现EnvironmentAware等一系列Aware接口获取到Spring内部的一些对象。prepareBeanFactory:

void addBeanPostProcessor(BeanPostProcessor beanPostProcessor);

ApplicationContextAwareProcessor核心的invokeAwareInterfaces方法:

private void invokeAwareInterfaces(Object bean) {if (bean instanceof Aware) {if (bean instanceof EnvironmentAware) {((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());}if (bean instanceof EmbeddedValueResolverAware) {((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver);}if (bean instanceof ResourceLoaderAware) {((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext);}if (bean instanceof ApplicationEventPublisherAware) {((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext);}if (bean instanceof MessageSourceAware) {((MessageSourceAware) bean).setMessageSource(this.applicationContext);}if (bean instanceof ApplicationContextAware) {((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);}}}

此方法是在bean的初始化过程中被调用的：

@Overridepublic Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {AccessControlContext acc = null;if (System.getSecurityManager() != null &&(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {acc = this.applicationContext.getBeanFactory().getAccessControlContext();}if (acc != null) {AccessController.doPrivileged(new PrivilegedAction