fresh 中的 prepareBeanFactory 方法
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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:
BeanExpressionResolver
PropertyEditorRegistrar
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()); } }
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1.BeanExpressionResolver
此接口只有一个实现: StandardBeanExpressionResolver。接口只含有一个方法:
/** * Evaluate the given value as an expression, if applicable; * return the value as-is otherwise. * @param value the value to check * @param evalContext the evaluation context * @return the resolved value (potentially the given value as-is) * @throws BeansException if evaluation failed */ Object evaluate(String value, BeanExpressionContext evalContext) throws BeansException;
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prepareBeanFactory 将一个此对象放入 BeanFactory:
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
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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:
/** * Add a PropertyEditorRegistrar to be applied to all bean creation processes. * <p>Such a registrar creates new PropertyEditor instances and registers them * on the given registry, fresh for each bean creation attempt. This avoids * the need for synchronization on custom editors; hence, it is generally * preferable to use this method instead of {@link #registerCustomEditor}. * @param registrar the PropertyEditorRegistrar to register */ void addPropertyEditorRegistrar(PropertyEditorRegistrar registrar);
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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()));
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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:
<bean class="org.springframework.beans.factory.config.CustomEditorConfigurer"> <property name="customEditors"> <map> <entry key="base.Cat" value="base.CatEditor" /> </map> </property></bean>
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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:
/** * Add a new BeanPostProcessor that will get applied to beans created * by this factory. To be invoked during factory configuration. * <p>Note: Post-processors submitted here will be applied in the order of * registration; any ordering semantics expressed through implementing the * {@link org.springframework.core.Ordered} interface will be ignored. Note * that autodetected post-processors (e.g. as beans in an ApplicationContext) * will always be applied after programmatically registered ones. * @param beanPostProcessor the post-processor to register */ void addBeanPostProcessor(BeanPostProcessor beanPostProcessor);
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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); } } }
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此方法是在 bean 的初始化过程中被调用的：
@Override public 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<Object>() { @Override public Object run() { invokeAwareInterfaces(bean); return null; } }, acc); } else { //处理bean对象是否实现相关的aware接口 invokeAwareInterfaces(bean); }
return bean; }
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4.依赖解析忽略
此部分设置哪些接口在进行依赖注入的时候应该被忽略:
beanFactory.ignoreDependencyInterface(EnvironmentAware.class); beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class); beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class); beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class); beanFactory.ignoreDependencyInterface(MessageSourceAware.class); beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
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5.bean 伪装
有些对象并不在 BeanFactory 中，但是我们依然想让它们可以被装配，这就需要伪装一下:
// 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);
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伪装关系保存在一个 Map<Class<?>, Object>里。
6.LoadTimeWeaver
如果配置了此 bean，那么：
// 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())); }
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这个东西具体是干什么的以后会进行相关的说明，这里先记得有这么个东西存在就行。
7.注册环境
// 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()); }
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没啥可讲的，需要注意的是 containsLocalBean 不会去父 BeanFactory 寻找。
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