Tomcat请求处理(一) -- 服务器端口监听

Tomcat请求处理(一) -- 服务器端口监听

其实tomcat在哪个类中监听请求的代码很容易找到：

在org.apache.tomcat.util.net.JIoEndpoint$Acceptor#run()中的这么一句：

Socket socket = serverSocketFactory.acceptSocket(serverSocket);

可是ServerSocketFactory是个抽象类，我还是很想知道整个过程的来龙去脉的。

那就要还是从初始化开始，当Tomcat的HTTP Connector初始化，会org.apache.coyote.http11.Http11Protocol调用它的init()方法。

在这个init()方法中，又调用了org.apache.tomcat.util.net.JIoEndpoint#init()，代码如下：

public void init() throws Exception {
    if (initialized)
        return;

    // acceptor线程的数量
    if (acceptorThreadCount == 0) {
        acceptorThreadCount = 1;
    }

    // 返回DefaultServerSocketFactory类对象做为ServerSocketFactory的实例
    if (serverSocketFactory == null) {
        serverSocketFactory = ServerSocketFactory.getDefault();
    }
    // 创建ServerSocket
    if (serverSocket == null) {
        try {
            if (address == null) {
                serverSocket = serverSocketFactory.createSocket(port, backlog);
            } else {
                serverSocket = serverSocketFactory.createSocket(port, backlog, address);
            }
        } catch (BindException be) {
            if (address == null)
                throw new BindException(be.getMessage() + ":" + port);
            else
                throw new BindException(be.getMessage() + " " + address.toString() + ":" + port);
        }
    }

    initialized = true;

}

public void init() throws Exception { if (initialized) return; // acceptor线程的数量 if (acceptorThreadCount == 0) { acceptorThreadCount = 1; } // 返回DefaultServerSocketFactory类对象做为ServerSocketFactory的实例 if (serverSocketFactory == null) { serverSocketFactory = ServerSocketFactory.getDefault(); } // 创建ServerSocket if (serverSocket == null) { try { if (address == null) { serverSocket = serverSocketFactory.createSocket(port, backlog); } else { serverSocket = serverSocketFactory.createSocket(port, backlog, address); } } catch (BindException be) { if (address == null) throw new BindException(be.getMessage() + ":" + port); else throw new BindException(be.getMessage() + " " + address.toString() + ":" + port); } } initialized = true; }

现在已经知道了文章最初提到的serverSocketFactory引用的是一个DefaultServerSocketFactory类的对象。并且在这里创建了一个ServerSocket对象。

当Tomcat初始化完毕执行一些列开启服务的动作时，HTTP Connector也会执行它的start()方法，然后会调用Http11Protocol的start()方法，最后程序会执行到JIoEndpoint#start()，下面来看一下：

public void start() throws Exception {
    if (!initialized) {
        init();
    }

    if (!running) {
        running = true;
        paused = false;

        // 先初始化一些Worker
        if (executor == null) {
            workers = new WorkerStack(maxThreads);
        }

        // 开启Acceptor线程，默认只开启一个Acceptor线程，见JIoEndpoint#init()。
        for (int i = 0; i < acceptorThreadCount; i++) {
            Thread acceptorThread = new Thread(new Acceptor(), getName() + "-Acceptor-" + i);
            acceptorThread.setPriority(threadPriority);
            acceptorThread.setDaemon(daemon);
            acceptorThread.start();
        }
    }
}

public void start() throws Exception { if (!initialized) { init(); } if (!running) { running = true; paused = false; // 先初始化一些Worker if (executor == null) { workers = new WorkerStack(maxThreads); } // 开启Acceptor线程，默认只开启一个Acceptor线程，见JIoEndpoint#init()。 for (int i = 0; i < acceptorThreadCount; i++) { Thread acceptorThread = new Thread(new Acceptor(), getName() + "-Acceptor-" + i); acceptorThread.setPriority(threadPriority); acceptorThread.setDaemon(daemon); acceptorThread.start(); } } }

这样，就开启了一个Acceptor线程，接下来看一看这个线程做了什么东西。

public void run() {
    while (running) {

        while (paused) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
            }
        }

        try {
            // 开始监听端口
            Socket socket = serverSocketFactory.acceptSocket(serverSocket);
            // 初始化Socket
            serverSocketFactory.initSocket(socket);
            if (!processSocket(socket)) {
                try {
                    socket.close();
                } catch (IOException e) {
                }
            }
        } catch (IOException x) {
            if (running)
                log.error(sm.getString("endpoint.accept.fail"), x);
        } catch (Throwable t) {
            log.error(sm.getString("endpoint.accept.fail"), t);
        }
    }

}

public void run() { while (running) { while (paused) { try { Thread.sleep(1000); } catch (InterruptedException e) { } } try { // 开始监听端口 Socket socket = serverSocketFactory.acceptSocket(serverSocket); // 初始化Socket serverSocketFactory.initSocket(socket); if (!processSocket(socket)) { try { socket.close(); } catch (IOException e) { } } } catch (IOException x) { if (running) log.error(sm.getString("endpoint.accept.fail"), x); } catch (Throwable t) { log.error(sm.getString("endpoint.accept.fail"), t); } } }

至此，Tomcat开启了一个端口进行请求的监听。