SpringBoot (3) WebServerApplicationContext

SpringBoot版本

SpringBoot 2.1.6

WebServerApplicationContext

在run方法中，通过反射创建了AnnotationConfigServletWebServerApplicationContext

 public ConfigurableApplicationContext run(String... args) {
		 ...
         ConfigurableApplicationContext context = null;
		 ...
		try {
			...
			context = createApplicationContext();
			...
			prepareContext(context, environment, listeners, applicationArguments, printedBanner);
			refreshContext(context);
			afterRefresh(context, applicationArguments);
			...
		}
		catch (Throwable ex) {
			...
		}
		...
		return context;
	}

prepareContext

准备context的环境，应用相关的后置处理器，调用ApplicationContextInitializer的initialize初始化 ,加载资源，加载相关bean

refreshContext

refreshContext使用了refresh，调用了AbstractApplicationContext的refresh

private void refreshContext(ConfigurableApplicationContext context) {
		refresh(context);
		if (this.registerShutdownHook) {
			try {
				context.registerShutdownHook();
			}
			catch (AccessControlException ex) {
				// Not allowed in some environments.
			}
		}
	}

refresh属于Spring framework中的操作

通过ConfigurationClassPostProcessor来扫描注解@ComponentScan，@Import(AutoConfigurationImportSelector)

创建server

在创建了AnnotationConfigServletWebServerApplicationContext后的refresh过程中OnRefresh，创建了WebServer

@Override
protected void onRefresh() {
   super.onRefresh();
   try {
      createWebServer();
   }
   catch (Throwable ex) {
      throw new ApplicationContextException("Unable to start web server", ex);
   }
}

通过ServletWebServerFactory创建了WebServer,在通过ServletContextInitializer 的接口做init。

public interface ServletContextInitializer {

   /**
    * Configure the given {@link ServletContext} with any servlets, filters, listeners
    * context-params and attributes necessary for initialization.
    * @param servletContext the {@code ServletContext} to initialize
    * @throws ServletException if any call against the given {@code ServletContext}
    * throws a {@code ServletException}
    */
   void onStartup(ServletContext servletContext) throws ServletException;

}

启动server

重写了finishRefresh，开始启动server

@Override
protected void finishRefresh() {
   super.finishRefresh();
   WebServer webServer = startWebServer();
   if (webServer != null) {
      publishEvent(new ServletWebServerInitializedEvent(webServer, this));
   }
}

小结

ApplicationContext的类型是可以通过参数控制，但是常用的也就是web和非web，还有一种是Reactive,可以看出SpringBoot完全是靠注解走遍所有流程，文中已经省略了涉及的Spring框架，如果觉得不明白，还是去先看明白Spring框架，再看这篇水文。

通过对Spring框架的扩展，SpringBoot在执行过程中context有了，servlet也有了，我们所需要的资源都ok了。

OK，又水一篇

key word

AnnotationConfigServletWebServerApplicationContext

主目录

SpringBoot框架及源码分析

SpringBoot (3) WebServerApplicationContext