Tomcat源码简要解析

Tomcat架构图

tomcat架构图.png

源码流程如下

###找到启动类
org.apache.catalina.startup.Bootstrap.main()
 ->org.apache.catalina.startup.Bootstrap.init()
  ->org.apache.catalina.startup.Catalina.load()
   ->org.apache.catalina.startup.Catalina.createStartDigester()  解析xml文件
  ->org.apache.catalina.startup.Catalina.getServer()   
   ->org.apache.catalina.util.LifecycleBase.init()
    ->org.apache.catalina.core.StandardServer.initInternal()  备注,这里的是StandardServer
    // Initialize our defined Services
    for (int i = 0; i < services.length; i++) {
       services[i].init();
    }
    
     ->org.apache.catalina.util.LifecycleBase.init()
      ->org.apache.catalina.core.StandardService.initInternal() 备注,这里的是StandardService
       ->engine.init();
       ->executor.init();   在for循环里面初始化,即executor有多个
       ->mapperListener.init();
       ->connector.init();  在for循环里面初始化  即connector有多个
        ->org.apache.catalina.connector.Connector.initInternal() 
         ->protocolHandler.init();
          ->org.apache.coyote.AbstractProtocol.init()
           ->org.apache.tomcat.util.net.AbstractEndpoint.init()
            ->org.apache.tomcat.util.net.AbstractEndpoint.bindWithCleanup()
             ->org.apache.tomcat.util.net.NioEndpoint.bind()
              ->org.apache.tomcat.util.net.NioEndpoint.initServerSocket()
               ->serverSock.socket().bind(addr,getAcceptCount());  调用socket.bind()
       

整个启动流程图如下:

Tomcat启动流程图.png

结构图如下

Tomcat结构图.png

小结

我们常用的如下

public class LoginServlet extends  MyServlet {
    @Override
    void service(MyTomcat.Request request, MyTomcat.Response response) {

    }
}

那么Tomcat容器到底是什么?

伪代码如下

public class MyTomcat {
        //1.网络连接
        ServerSocket serverSocket = new ServerSocket(8080);
        Socket accept = serverSocket.accept();

        List<MyServlet> list = new ArrayList<>();

        //2.根据连接获取输入输出
        InputStream in = accept.getInputStream();
        Request request = new Request(in);
        OutputStream out = accept.getOutputStream();
        Response response = new Response(out);

        //解析xml文件  添加servlet
        //LoginServlet loginServlet = new LoginServlet();
        list.add(loginServlet);
}

将请求和响应封装,提供统一的抽象方法

public abstract  class MyServlet {
    abstract void  service(MyTomcat.Request request, MyTomcat.Response response);
}