Spring MVC系列（6）-DispatcherServlet初始化源码分析

前言

我们知道servlet程序需要使用servlet容器运行，那么DispatcherServlet是如何在spring boot内嵌tomcat容器进行初始化的呢？

1. 启动tomcat

首先点击启动类，启动spring boot 程序，然后进入了ServletWebServerApplicationContext类的createWebServer方法，开始创建一个web服务器。

    private void createWebServer() {
   
     
        WebServer webServer = this.webServer;
        ServletContext servletContext = this.getServletContext();
        if (webServer == null && servletContext == null) {
   
     
            StartupStep createWebServer = this.getApplicationStartup().start("spring.boot.webserver.create");
            // 1. 获取容器工厂
            ServletWebServerFactory factory = this.getWebServerFactory();
            createWebServer.tag("factory", factory.getClass().toString());
            // 2. 使用工厂获取容器
            this.webServer = factory.getWebServer(new ServletContextInitializer[]{
   
     this.getSelfInitializer()});
            createWebServer.end();
            this.getBeanFactory().registerSingleton("webServerGracefulShutdown", new WebServerGracefulShutdownLifecycle(this.webServer));
            this.getBeanFactory().registerSingleton("webServerStartStop", new WebServerStartStopLifecycle(this, this.webServer));
        } else if (servletContext != null) {
   
     
            try {
   
     
                this.getSelfInitializer().onStartup(servletContext);
            } catch (ServletException var5) {
   
     
                throw new ApplicationContextException("Cannot initialize servlet context", var5);
            }
        }
		// 3. 初始化PropertySources配置
        this.initPropertySources();
    }