2019独角兽企业重金招聘Python工程师标准>>> 
前言
本文转自“天河聊技术”微信公众号
本次主要介绍bean初始化、依赖注入后续的实现和其他入口
正文
找到这个方法
org.springframework.context.support.AbstractApplicationContext#refresh
这一行
finishRefresh();
进入
org.springframework.context.support.AbstractApplicationContext#finishRefresh
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).清除上下文级别的资源缓存(例如扫描的ASM元数据)。
clearResourceCaches();
// Initialize lifecycle processor for this context.为这个上下文初始化生命周期处理器。
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.首先传播刷新到生命周期处理器。
getLifecycleProcessor().onRefresh();
// Publish the final event.发布最后的事件。
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
这一行
initLifecycleProcessor();
初始化生命周期处理器
进入
org.springframework.context.support.AbstractApplicationContext#initLifecycleProcessor初始化LifecycleProcessor。如果上下文没有定义，则使用DefaultLifecycleProcessor
protected void initLifecycleProcessor() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(LIFECYCLE_PROCESSOR_BEAN_NAME)) {
this.lifecycleProcessor =
beanFactory.getBean(LIFECYCLE_PROCESSOR_BEAN_NAME, LifecycleProcessor.class);
if (logger.isDebugEnabled()) {
logger.debug("Using LifecycleProcessor [" + this.lifecycleProcessor + "]");
}
}
else {
DefaultLifecycleProcessor defaultProcessor = new DefaultLifecycleProcessor();
defaultProcessor.setBeanFactory(beanFactory);
this.lifecycleProcessor = defaultProcessor;
beanFactory.registerSingleton(LIFECYCLE_PROCESSOR_BEAN_NAME, this.lifecycleProcessor);
if (logger.isDebugEnabled()) {
logger.debug("Unable to locate LifecycleProcessor with name '" +
LIFECYCLE_PROCESSOR_BEAN_NAME +
"': using default [" + this.lifecycleProcessor + "]");
}
}
}
回到这个方法
org.springframework.context.support.AbstractApplicationContext#refresh
这一行
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.销毁已经创建的单例，以避免悬空资源。
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
异常处理
返回
org.springframework.web.context.ContextLoader#initWebApplicationContext这一行
// 把spring上下文放在servlet上下文上 servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
返回
@Override
public void contextInitialized(ServletContextEvent event) {
initWebApplicationContext(event.getServletContext());
}
我跟踪的顺序是跟着servlet容器启动这个入口看来跟踪的，还有两个入口给大家介绍下
ClassPathXmlApplicationContext
这个方法
org.springframework.context.support.ClassPathXmlApplicationContext#ClassPathXmlApplicationContext(java.lang.String)
public ClassPathXmlApplicationContext(String configLocation) throws BeansException {
this(new String[] {configLocation}, true, null);
}
参数是传入一个bean定义配置文件
进入org.springframework.context.support.ClassPathXmlApplicationContext#ClassPathXmlApplicationContext(java.lang.String[], boolean, org.springframework.context.ApplicationContext)这个方法
public ClassPathXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
进入org.springframework.context.support.AbstractApplicationContext#refresh这个方法，剩下的以往的文章中都介绍过了
FileSystemXmlApplicationContext
找到org.springframework.context.support.FileSystemXmlApplicationContext#FileSystemXmlApplicationContext(java.lang.String)这个方法
public FileSystemXmlApplicationContext(String configLocation) throws BeansException {
this(new String[] {configLocation}, true, null);
}
参数也是传入一个bean定义配置文件
进入
org.springframework.context.support.FileSystemXmlApplicationContext#FileSystemXmlApplicationContext(java.lang.String[], boolean, org.springframework.context.ApplicationContext)
public FileSystemXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}
进入org.springframework.context.support.AbstractApplicationContext#refresh这个方法，剩下的以往的文章都介绍过了，applicationContext的生涯新实现就解析完了
最后
本次介绍到这里，以上内容仅供参考。