Springboot内嵌tomcat应用原理深入分析

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
	<exclusions>
		<exclusion>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-tomcat</artifactId>
		</exclusion>
	</exclusions>
</dependency>
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-undertow</artifactId>
</dependency>

@Override
public WebServer getWebServer(ServletContextInitializer... initializers) {
	if (this.disableMBeanReGIStry) {
		Registry.disableRegistry();
	}
	// 实例化一个tomcat
	Tomcat tomcat = new Tomcat();
	File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");
	// 设置tomcat的临时工作目录
	tomcat.setBaseDir(baseDir.getAbsolutePath());
	// 默认使用Http11NIOProtocol实例化connector
	Connector connector = new Connector(this.protocol);
	connector.setThrowOnFailure(true);
	// 给service添加connector
	tomcat.getService().addConnector(connector);
	customizeConnector(connector);
	tomcat.setConnector(connector);
	// 关闭热部署
	tomcat.getHost().setAutoDeploy(false);
	// 配置engine
	configureEngine(tomcat.getEngine());
	for (Connector additionalConnector : this.additionalTomcatConnectors) {
		tomcat.getService().addConnector(additionalConnector);
	}
	prepareContext(tomcat.getHost(), initializers);
	// 实例化TomcatWebServer时会将DispatcherServlet以及一些Filter添加到tomcat
	return getTomcatWebServer(tomcat);
}

@Override
protected void onRefresh() {
	super.onRefresh();
	try {
		// 通过Servlet容器工厂TomcatServletWebServerFactory，获取Servlet容器tomcat
		createWebServer();
	}
	catch (Throwable ex) {
		throw new ApplicationContextException("Unable to start web server", ex);
	}
}

@Override
protected void finishRefresh() {
	super.finishRefresh();
	// 实例化（在tomcat启动时就要完成实例化的Servlet：loadStartUp > 0），打印启动完成日志。
	WebServer webServer = startWebServer();
	if (webServer != null) {
		publishEvent(new ServletWebServerInitializedEvent(webServer, this));
	}
}