本文是针对Srping的ClassPathXMLApplicationContext来进行源码解析,在本篇博客中将不会讲述spring Xml解析注册代码,因为ApplicationContext是BeanFactory的扩展版本,ApplicationContext的GetBean和xml解析注册BeanDefinition都是用一套代码,如果您是第一次看请先看一下XMLBeanFactory解析和BeanFactory.GetBean源码解析:
- XMLBeanFactory源码解析地址:https://www.cnblogs.com/technology-blog/p/14543685.html
- BeanFactory.getBean源码解析地址:https://www.cnblogs.com/technology-blog/p/14543902.html
作者整理了spring-framework 5.x的源码注释,代码已经上传者作者的GitHub了,可以让读者更好的理解,地址:
- 接下来直接上源码:
package lantao;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.lantao.UserBean;
public class ApplicationContextTest {
public static void main(String[] args) {
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-bean.xml");
UserBean userBean = (UserBean) applicationContext.getBean("userBean");
System.out.println(userBean.getName());
}
}
在这里直接使用ClassPathXmlApplicationContext进行xml解析,在这里xml解析的代码和GetBean的代码就不过多的描述了,ApplicationContext是BeanFactory的扩展,所以想要看这两部分源码的请看作者的上两篇博客Sprin源码解析;
- 接下来我们看一下ClassPathXmlApplicationContext的源码:
/**
* Create a new ClassPathXmlApplicationContext with the given parent,
* loading the definitions from the given XML files.
* @param configLocations array of resource locations
* @param refresh whether to automatically refresh the context,
* loading all bean definitions and creating all singletons.
* Alternatively, call refresh manually after further configuring the context.
* @param parent the parent context
* @throws BeansException if context creation failed
* @see #refresh()
*/
public ClassPathXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
super(parent);
// 支持解析多文件
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
在setConfigLocations方法中将资源文件放入configLocations全局变量中,,并且支持多文件解析,接下来我们你看一下重点,refresh方法;
- 源码refresh方法:
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
// 准备刷新上下文
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
// 对beanFactory的各种功能填充,加载beanFactory,经过这个方法 applicationContext就有了BeanFactory的所有功能
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
// 对beanFactory进行各种功能填充
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
// 允许在context子类中对BeanFactory进行post-processing。
// 允许在上下文子类中对Bean工厂进行后处理
// 可以在这里进行 硬编码形式的 BeanFactoryPostProcessor 调用 addBeanFactoryPostProcessor
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
// 激活各种BeanFactory处理器 BeanFactoryPostProcessors是在实例化之前执行
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
// 注册 拦截Bean创建 的Bean处理器,这里只是注册,真正地调用在getBean的时候 BeanPostProcessors实在init方法前后执行 doCreateBean方法中的 实例化方法中执行
// BeanPostProcessor执行位置:doCreateBean --> initializeBean --> applyBeanPostProcessorsBeforeInitialization 和 applyBeanPostProcessorsAfterInitialization
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
//为上下文初始化Message源,(比如国际化处理) 这里没有过多深入
initMessageSource();
// Initialize event multicaster for this context.
//初始化应用消息广播,并放入 applicationEventMulticaster bean中
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
//留给子类来初始化其它的bean
onRefresh();
// Check for listener beans and register them.
//在所有注册的bean中查找Listener bean,注册到消息广播器中
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
//初始化剩下的单实例
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
//完成刷新过程,通知生命周期护处理器lifecycleProcessor刷新过程,同时发出ContextRefreshEvent通知别人(LifecycleProcessor 用来与所有声明的bean的周期做状态更新)
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
对于ApplicationContext来说,refresh方法几乎涵盖了所有的基础和扩展功能,接下来看一下这个方法都做了什么;
- 刷新上下文,初始化前的准备工作;
- 加载beanFactory,经过这个方法 applicationContext就有了BeanFactory的所有功能
- 对beanFactory进行各种功能填充
- 允许在这里对BeanFactory的二次加工,例如:可以在这里进行硬编码方法的对BeanFactory进行BeanFactoryPostProcessor或BeanPostProcessor的操作;在这里简单说一下BeanFactoryPostProcessor是在bean实例化之前执行的,BeanPostProcessor是在初始化方法前后执行的,BeanFactoryPostProcessor操作的是BeanFactoryBeanPostProcessor操作的是Bean,其次这里还涉及了一个扩展BeanDefinitionRegistryPostProcessor它是继承了BeanFactoryPostProcessor,并且还有自己的定义方法 postProcessBeanDefinitionRegistry,这个方法可以操作BeanDefinitionRegistry,BeanDefinitionRegistry有个最主要的方法就是registerBeanDefinition,可以注册BeanDefinition,可以用这方法来处理一下不受spring管理的一下bean;
- 处理所有的BeanFactoryPostProcessor,也可以说是激活BeanFactory处理器,在这个方法里会先处理BeanDefinitionRegistryPostProcessor,在处理BeanFactoryPostProcessor,因为BeanDefinitionRegistryPostProcessor有自己的定义,所以先执行;
- 注册BeanPostProcessors ,这里只是注册,真正地调用在getBean的时候 BeanPostProcessors是在init方法前后执行 BeanPostProcessor执行位置:doCreateBean --> initializeBean --> applyBeanPostProcessorsBeforeInitialization 和 applyBeanPostProcessorsAfterInitialization方法中;
- 为上下文初始化Message源,(比如国际化处理) 这里没有过多深入;
- 初始化应用消息广播,初始化 applicationEventMulticaster ,判断使用自定义的还是默认的;
- 留给子类来初始化其它的bean;
- 在所有注册的bean中查找 ApplicationListener bean,注册到消息广播器中;
- 初始化剩下的单实例(非懒加载),这里会是涉及conversionService,LoadTimeWeaverAware,冻结BeanFactory,初始化Bean等操作;
- 完成刷新过程,包括 清除 下文级资源(例如扫描的元数据),通知生命周期处理器lifecycleProcessor并strat,同时publish Event发出ContextRefreshEvent通知别人;
- 先来看prepareRefresh方法:
/**
* Prepare this context for refreshing, setting its startup date and
* active flag as well as performing any initialization of property sources.
*/
protected void prepareRefresh() {
// Switch to active.
this.startupDate = System.currentTimeMillis();
// 标志,指示是否已关闭此上下文
this.closed.set(false);
// 指示此上下文当前是否处于活动状态的标志
this.active.set(true);
if (logger.isDebugEnabled()) {
if (logger.isTraceEnabled()) {
logger.trace("Refreshing " + this);
}
else {
logger.debug("Refreshing " + getDisplayName());
}
}
// Initialize any placeholder property sources in the context environment.
// 对上下文环境中的任何属性源进行分类。
initPropertySources();
// Validate that all properties marked as required are resolvable:
// see ConfigurablePropertyResolver#setRequiredProperties,
//验证标示为必填的属性信息是否都有了 ConfigurablePropertyResolver#setRequiredProperties 方法
getEnvironment().validateRequiredProperties();
// Store pre-refresh ApplicationListeners...
if (this.earlyApplicationListeners == null) {
this.earlyApplicationListeners = new LinkedHashSet<>(this.applicationListeners);
}
else {
// Reset local application listeners to pre-refresh state.
this.applicationListeners.clear();
this.applicationListeners.addAll(this.earlyApplicationListeners);
}
// Allow for the collection of early ApplicationEvents,
// to be published once the multicaster is available...
this.earlyApplicationEvents = new LinkedHashSet<>();
}
一眼望去,可能觉得这个方法没有做什么,其实这方法中除了Closed和Active,最重要的是initPropertySources和getEnvironment().validateRequiredProperties()方法;
- initPropertySources证符合Spring的开放式结构设计,给用户最大扩展Spring的能力。用户可以根据自身的需要重写initPropertySourece方法,并在方法中进行个性化的属性处理及设置。
- validateRequiredProperties则是对属性进行验证,那么如何验证呢?举个融合两句代码的小例子来理解。
例如现在有这样一个需求,工程在运行过程中用到的某个设置(例如VAR)是从系统环境变量中取得的,而如果用户没有在系统环境变量中配置这个参数,工程不会工作。这一要求也各种各样的解决办法,在Spring中可以这么做,可以直接修改Spring的源码,例如修改ClassPathXmlApplicationContext.当然,最好的办法是对源码进行扩展,可以自定义类:
public class MyClassPathXmlApplicationContext extends ClassPathXmlApplicationContext{ public MyClassPathXmlApplicationContext(String.. configLocations){ super(configLocations); } protected void initPropertySources(){ //添加验证要求 getEnvironment().setRequiredProterties("VAR"); } }
自定义了继承自ClassPathXmlApplicationContext的MyClassPathXmlApplicationContext,并重写了initPropertySources方法,在方法中添加了个性化需求,那么在验证的时候也就是程序走到getEnvironment().validateRequiredProperties()代码的时候,如果系统并没有检测到对应VAR的环境变量,将抛出异常。当然我们还需要在使用的时候替换掉原有的ClassPathXmlApplicationContext:
public static void main(Stirng[] args){ ApplicationContext bf = new MyClassPathXmlApplicationContext("myTest.xml"); User user = (User)bf.getBean("testBean"); }
上述案例来源于:Spring源码深度解析(第二版)141页;
- 接下来看一下obtainFreshBeanFactory方法,在这里初始化DefaultListAbleBeanFactory并解析xml:
/**
* Tell the subclass to refresh the internal bean factory.
* @return the fresh BeanFactory instance
* @see #refreshBeanFactory()
* @see #getBeanFactory()
*/
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
return getBeanFactory();
}
/**
* This implementation performs an actual refresh of this context's underlying
* bean factory, shutting down the previous bean factory (if any) and
* initializing a fresh bean factory for the next phase of the context's lifecycle.
*/
@Override
protected final void refreshBeanFactory() throws BeansException {
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
// createBeanFactory方法直接新建一个DefaultListableBeanFactory,内部使用的是DefaultListableBeanFactory实例
DefaultListableBeanFactory beanFactory = createBeanFactory();
// 设置序列化id
beanFactory.setSerializationId(getId());
// 定制beanFactory工厂
customizeBeanFactory(beanFactory);
// 加载BeanDefinition
loadBeanDefinitions(beanFactory);
synchronized (this.beanFactoryMonitor) {
// 使用全局变量记录BeanFactory
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
}
}
看一下上述方法都做了什么:
判断BeanFactory是否存在,如果存在则销毁所有Bean,然后关闭BeanFactory;
使用createBeanFactory方法直接新建一个DefaultListableBeanFactory,内部使用的是DefaultListableBeanFactory实例;
设置BeanFactory的设置序列化id
定制beanFactory工厂,也就是给allowBeanDefinitionOverriding(是否允许覆盖同名称的Bean)和allowCircularReferences(是否允许bean存在循环依赖),可通过setAllowBeanDefinitionOverriding和setAllowCircularReferences赋值,这里就可通过商编初始化方法中的initPropertySources方法来进行赋值;
package lantao; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MyApplicationContext extends ClassPathXmlApplicationContext { public MyApplicationContext(String... configLocations){ super(configLocations); } protected void initPropertySources(){ //添加验证要求 getEnvironment().setRequiredProperties("VAR"); // 在这里添加set super.setAllowBeanDefinitionOverriding(true); super.setAllowCircularReferences(true); } }
- 加载BeanDefinition,就是解析xml,循环解析,这里就不看了,如果不了解看作者上篇博客;
- 下面看一下prepareBeanFactory方法源码:
/**
* Configure the factory's standard context characteristics,
* such as the context's ClassLoader and post-processors.
* @param beanFactory the BeanFactory to configure
*/
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
// 设置BeanFactory的classLoader为当前context的classloader
beanFactory.setBeanClassLoader(getClassLoader());
// Spel语言解析器
// 设置BeanFactory的表达式语言处理器 Spring3中增加了表达式语言的支持
// 默认可以使用#{bean.xxx}的形式来调用相关属性值
// 在Bean实例化的时候回调用 属性填充的方法(doCreateBean 方法中的 populateBean 方法中的 applyPropertyValues 方法中的 evaluateBeanDefinitionString ) 就会判断beanExpressionResolver是否为null操作
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
// 为BeanFactory增加一个默认的 PropertyEditor 这个主要对bean的属性等设置管理的一个工具 增加属性注册编辑器 例如:bean property 类型 date 则需要这里
// beanFactory会在初始化 BeanWrapper(initBeanWrapper)中调用 ResourceEditorRegistrar 的 registerCustomEditors 方法
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// Configure the bean factory with context callbacks.
// ApplicationContextAwareProcessor --> postProcessBeforeInitialization
// 注册 BeanPostProcessor BeanPostProcessor 实在实例化前后执行的
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
// 设置几个忽略自动装配的接口 在addBeanPostProcessor方法中已经对下面几个类做了处理,他们就不是普通的bean了,所以在这里spring做bean的依赖的时候忽略
// doCreateBean 方法中的 populateBean 方法中的 autowireByName 或 autowireByType 中的 unsatisfiedNonSimpleProperties 中的 !isExcludedFromDependencyCheck(pd) 判断,
// 在属性填充的时候回判断依赖,如果存在下属几个则不做处理 对于下面几个类可以做implements操作
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.
// 设置几个注册依赖 参考spring源码深度解析原文:当注册依赖解析后,例如但那个注册了对BeanFactory。class的解析依赖后,当bean的属性注入的时候,一旦检测到属性为BeanFactory的类型变回将beanFactory 实例注入进去
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.
// 寄存器早期处理器,用于检测作为ApplicationListener的内部bean。
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// Detect a LoadTimeWeaver and prepare for weaving, if found.
// 增加了对AxpectJ的支持
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.
// 添加默认的系统环境bean
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());
}
}
不说废话,直接看这个方法都做了什么:
设置BeanFactory的classLoader为当前context的classloader;
设置BeanFactory的表达式语言处理器 Spring3中增加了Spel表达式语言的支持, 默认可以使用#{bean.xxx}的形式来调用相关属性值,
在Bean实例化的时候回调用 属性填充的方法(doCreateBean 方法中的 populateBean 方法中的 applyPropertyValues 方法中的 evaluateBeanDefinitionString ) 就会判断beanExpressionResolver是否为null操作,如果不是则会使用Spel表达式规则解析
<?xml version="1.0" encoding="UTF-8" ?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="testOneBean" class="lantao.bean.TestOneBean"> <property name="testTwoBean" value="#{testTWoBean}"/> </bean> <bean id="testTWoBean" class="lantao.bean.TestTwoBean"/> <!-- 上面 相当于 下边 --> <bean id="testOneBean1" class="lantao.bean.TestOneBean"> <property name="testTwoBean" ref="testTWoBean1"/> </bean> <bean id="testTWoBean1" class="lantao.bean.TestTwoBean"/> </beans>
- 为BeanFactory增加一个默认的 PropertyEditor 这个主要对bean的属性等设置管理的一个工具 增加属性注册编辑器 例如:User类中 startDate 类型 date 但是xml property的value是2019-10-10,在启动的时候就会报错,类型转换不成功,这里可以使用继承PropertyEditorSupport这个类机型重写并注入即可使用;beanFactory会在初始化BeanWrapper (initBeanWrapper)中调用 ResourceEditorRegistrar 的 registerCustomEditors 方法进行初始化;
配置BeanPostProcessor,这里配置的是ApplicationContextAwareProcessor,上边我们说了,BeanPostProcessor是在初始化方法Init前后执行,看一下ApplicationContextAwareProcessor的Before和After方法:
@Override @Nullable public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException { AccessControlContext acc = null; // 该方法也会在 BeanFactory 实例化bean 中调用 doCreateBean --> initializeBean --> applyBeanPostProcessorsBeforeInitialization --> postProcessBeforeInitialization // 如果实例化的类实现了 invokeAwareInterfaces 方法中的判断类 则会调用初始方法赋值 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((PrivilegedAction<Object>) () -> { invokeAwareInterfaces(bean); return null; }, acc); } else { invokeAwareInterfaces(bean); } return bean; } 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); } } } @Override public Object postProcessAfterInitialization(Object bean, String beanName) { return bean; }
在Before方法中调用了invokeAwareInterfaces方法,在invokeAwareInterfaces方法中做了类型 instanceof 的判断,意思就是如果这个Bean实现了上述的Aware,则会初始会一下资源,比如实现了ApplicationContextAware,就会setApplicationContext,这里相信大家都用过,就不多说了;
设置几个忽略自动装配的接口 在addBeanPostProcessor方法中已经对下面几个类做了处理,他们就不是普通的bean了,所以在这里spring做bean的依赖的时候忽略,在doCreateBean 方法中的 populateBean 方法中的 autowireByName 或 autowireByType 中的 unsatisfiedNonSimpleProperties 中的 !isExcludedFromDependencyCheck(pd) 判断,如果存在则不做依赖注入了;
设置几个注册依赖 参考spring源码深度解析原文:当注册依赖解析后,例如当注册了对BeanFactory的解析依赖后,当bean的属性注入的时候,一旦检测到属性为BeanFactory的类型便会将beanFactory 实例注入进去;
添加BeanPostProcessor,这里是添加ApplicationListener,是寄存器早期处理器;这里可以看作者的源码测试,在spring-context的test测试类下有;
增加了对AxpectJ的支持
注册默认的系统环境bean,environment ,systemProperties,systemEnvironment;
- 上述就是对BeanFactory的功能填充,下面看postProcessBeanFactory:
postProcessBeanFactory方法是个空方法,允许在上下文子类中对Bean工厂进行后处理,例如:可以在这里进行 硬编码形式的 BeanFactoryPostProcessor 调用 addBeanFactoryPostProcessor,进行addBeanFactoryPostProcessor或者是BeanPostProcessor;
- 接下来看一下invokeBeanFactoryPostProcessors方法:
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();
// 对 BeanDefinitionRegistry 类型处理
if (beanFactory instanceof BeanDefinitionRegistry) {
// 强转
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
// 普通的处理器
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
//注册处理器
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
// 这里就是硬编码处理 因为这里是从 getBeanFactoryPostProcessors()方法获取的 可以硬编码从addBeanFactoryPostProcessor()方法添加
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
// 对于 BeanDefinitionRegistryPostProcessor 类型 在 BeanFactoryPostProcessor 的基础上还有自己的定义,需要先调用
BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor;
// 执行 继承 BeanDefinitionRegistryPostProcessor 类的 postProcessBeanDefinitionRegistry 方法
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
regularPostProcessors.add(postProcessor);
}
}
//上边的For循环只是调用了硬编码的 BeanDefinitionRegistryPostProcessor 中的 postProcessBeanDefinitionRegistry 方法,
// 但是 BeanFactoryPostProcessor 中的 postProcessBeanFactory 方法还没有调用,是在方法的最后一行
// invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
// invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); 这两个方法中执行的,
// 下面是自动处理器 获取类型是BeanDefinitionRegistryPostProcessor beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); 获取的
// 当前注册处理器
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
// 首先调用实现了 PriorityOrdered 的 BeanDefinitionRegistryPostProcessors
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 执行 BeanDefinitionRegistryPostProcessor类的postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
// 下一个 ,调用实现 Ordered 的 BeanDefinitionRegistryPostProcessors
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 执行 BeanDefinitionRegistryPostProcessor类的postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
// 最后,调用所有其他BeanDefinitionRegistryPostProcessors,直到不再显示其他BeanDefinitionRegistryPostProcessors 无序的
boolean reiterate = true;
while (reiterate) {
reiterate = false;
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 执行 BeanDefinitionRegistryPostProcessor类的postProcessBeanDefinitionRegistry方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
// 现在,调用到目前为止处理的所有处理器的 执行BeanFactoryPostProcessor 类的 postProcessBeanFactory 方法
// 这里执行的是 硬编码 和 非硬编码(自动)的 BeanFactoryPostProcessor 类的 postProcessBeanFactory 方法 分为硬编码处理器 和 普通处理器
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// 调用在上下文实例中注册的工厂处理器的postProcessBeanFactory方法。 就是硬编码 通过 addBeanFactoryPostProcessor 方法添加的BeanFactoryPostProcessor
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// 自动处理 非硬编码 获取类型为是BeanFactoryPostProcessor beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 实现 priorityOrdered 的
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
// 实现 Ordered 的
List<String> orderedPostProcessorNames = new ArrayList<>();
// 无序的
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();
}
上述代码看起来很多,但是总计起来就三件事:
- 执行硬编码的和主动注入的BeanDefinitionRegistryPostProcessor,调用postProcessBeanDefinitionRegistry方法;
- 执行硬编码的和主动注入的BeanFactoryPostProcessor,调用postProcessBeanFactory方法;
- 自动注入的可继承Ordered排序,priorityOrdered排序或无序;
上述测试在作者的spring源码congtext中lantao包下有测试用例;
- registerBeanPostProcessors方法源码:
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 使用 priorityOrdered保证顺序
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
// MergedBeanDefinitionPostProcessor
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
// 使用order保证顺序
List<String> orderedPostProcessorNames = new ArrayList<>();
// 无序的
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
// 进行add操作
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
// 首先 注册实现PriorityOrdered的 BeanPostProcessors 先排序PostProcessors
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
// 下一个,注册实现Ordered的BeanPostProcessors
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
// 现在,注册所有常规注册。无序的
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
// 最后,注册所有MergedBeanDefinitionPostProcessor类型的BeanPostProcessor,并非重复注册。
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
// 添加 ApplicationListener探测器
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
registerBeanPostProcessors方法代码还是比较长的,它和invokeBeanFactoryPostProcessors方法最主要的区别就是registerBeanPostProcessors只在这里注册,但不在这里调用,做的事情和invokeBeanFactoryPostProcessors差不多:
- 使用priorityOrdered,Ordered或无序保证顺序;
- 通过beanFactory.addBeanPostProcessor(postProcessor)进行注册;
很简单,代码篇幅很长,但是很好理解,这里可以简单看一下;
-
接下来是initMessageSource方法,这里作者没有过多的看源码,后续补上吧.......(抱歉)
-
initApplicationEventMulticaster源码:
/**
* Initialize the ApplicationEventMulticaster.
* Uses SimpleApplicationEventMulticaster if none defined in the context.
* @see org.springframework.context.event.SimpleApplicationEventMulticaster
*/
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// 使用自定义的 广播
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isTraceEnabled()) {
logger.trace("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {
// 使用spring 默认的广播
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
if (logger.isTraceEnabled()) {
logger.trace("No '" + APPLICATION_EVENT_MULTICASTER_BEAN_NAME + "' bean, using " +
"[" + this.applicationEventMulticaster.getClass().getSimpleName() + "]");
}
}
}
initApplicationEventMulticaster方法中主要就是判断是使用自定义的ApplicationEventMulticaster(广播器)还是使用呢Spring默认的SimpleApplicationEventMulticaster广播器;
-
onRefresh 方法是留个子类重写的,内容是空;
-
registerListeners方法:
/**
* Add beans that implement ApplicationListener as listeners.
* Doesn't affect other listeners, which can be added without being beans.
*/
protected void registerListeners() {
// Register statically specified listeners first.
// 注册 添加 ApplicationListener 这里通过硬编码 addApplicationListener 方法添加的
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let post-processors apply to them!
// 注册 添加 ApplicationListener 这里是自动注册添加的
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
// Publish early application events now that we finally have a multicaster...
// 发布早期的事件
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
registerListeners方法做了三件事情:
- 添加 ApplicationListener 这里通过硬编码 addApplicationListener 方法添加的;
- 添加 ApplicationListener 是通过自动注册添加的
- 发布早起事件
- finishBeanFactoryInitialization方法源码:
/**
* Finish the initialization of this context's bean factory,
* initializing all remaining singleton beans.
*/
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.
// conversionService 用于类型转换 ,比如 String 转Date
//判断BeanFactory中是否存在名称为“conversionService”且类型为ConversionService的Bean,如果存在则将其注入到beanFactory
// 判断有无自定义属性转换服务接口,并将其初始化,我们在分析bean的属性填充过程中,曾经用到过该服务接口。在TypeConverterDelegate类的convertIfNecessary方法中
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(
beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}
// Register a default embedded value resolver if no bean post-processor
// (such as a PropertyPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
// 得到所有的实现了LoadTimeWeaverAware接口的子类名称,初始化它们
// 如果有LoadTimeWeaverAware类型的bean则初始化,用来加载Spring Bean时织入第三方模块,如AspectJ,我们在后面详细讲解。
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
// 停止使用临时类加载器 就是在这里不让使用呢 ClassLoader 了
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
// 冻结所有bean定义,说明你注册的bean将不被修改或进行任何进一步的处理 就是不让改了 BeanDefinition
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons.
// 初始化所有非懒加载的 单例 bean 调用你getBean方法
beanFactory.preInstantiateSingletons();
}
finishBeanFactoryInitialization方法做了五件事情:
- 设置BeanFactory的conversionService,conversionService用于类型转换使用, 例如:User类中 startDate 类型 date 但是xml property的value是2019-10-10,在启动的时候就会报错,类型转换不成功,可以使用conversionService;书中170页有具体代码;
- 添加BeanFactory的addEmbeddedValueResolver,读取配置信息放到这里,可以通过EmbeddedValueResolverAware来获取,参考:https://www.cnblogs.com/winkey4986/p/7001173.html
- 得到所有的实现了LoadTimeWeaverAware接口的子类名称,初始化它们,用来加载Spring Bean时织入第三方模块,如AspectJ,我们在后面详细讲解。
- 停止使用临时类加载器 就是在这里不让使用呢 ClassLoader 了
- 冻结所有bean定义,说明你注册的bean将不被修改或进行任何进一步的处理 就是不让改了 BeanDefinition
- 初始化所有非懒加载的 单例 bean 调用你getBean方法,循环所有bean并实例化 条件是:单例,非Abstract 非懒加载
- 最后的一个方法finishRefresh:
/**
* Finish the refresh of this context, invoking the LifecycleProcessor's
* onRefresh() method and publishing the
* {@link org.springframework.context.event.ContextRefreshedEvent}.
*/
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).
// 清除 下文级资源(例如扫描的元数据)。
clearResourceCaches();
// Initialize lifecycle processor for this context.
// 在当前context中初始化 lifecycle
// lifecycle 有自己的 start/ stop方法,实现此接口后spring保证在启动的时候调用start方法开始生命周期 关闭的时候调用 stop方法结束生命周期
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
// onRefresh 启动所有实现了 lifecycle 的方法
getLifecycleProcessor().onRefresh();
// Publish the final event.
// 当ApplicationContext初始化完成发布后发布事件 处理后续事宜
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
// 这里 没明白》。。
LiveBeansView.registerApplicationContext(this);
}
finishRefresh方法是ApplicationContext初始化的最后一个方法了,他做了一些结尾的事情:
- 清除 下文级资源(例如扫描的元数据)。
- 在当前context中初始化 lifecycle,lifecycle 有自己的 start/ stop方法,实现此接口后spring保证在启动的时候调用start方法开始生命周期 关闭的时候调用 stop方法结束生命周期。
- onRefresh 启动所有实现了 lifecycle 的方法,调用了start方法。
- 当ApplicationContext初始化完成发布事件 处理后续事宜。
- LiveBeansView.registerApplicationContext(this)这个代码没有太明白,有大神可以留言;
至此ApplicationContext的源码就都已经分析完成了,其中有很多地方很难懂,大家可以对应着源码一起看,会好理解一些,如果其中有错误,欢迎大神指点,在下方留言。