本文接下来介绍tomcat的默认连接器，Tomcat中的默认连接器必须满足以下要求：
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实现org.apache.catalina.Connector接口
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负责创建实现org.apache.catalina.Request接口的Request对象
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负责创建实现org.apache.catalina.Response接口的Response对象
org.apache.catalina.Connector接口最重要的方法是getContainer() 、setContainer()、creatRequest()、 creatResponse()，setContainer()方法用于设置相关联的servlet容器，getContainer()方法获取相关连的servlet容器，creatRequest()方法为http请求创建request对象，creatResponse()方法创建response对象
下面来分析HttpConnector类实现，HttpConnector类同时实现了org.apache.catalina.Connector接口org.apache.catalina.Lifecycle接口（用于生命周期管理）、java.lang.Runnable接口（多线程接口）
在HttpConnector对象的初始化方法initialize()里面，调用私有方法open()，创建ServerSocket实例
private ServerSocket open() throws IOException, KeyStoreException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException, KeyManagementException { // Acquire the server socket factory for this Connector ServerSocketFactory factory = getFactory(); // If no address is specified, open a connection on all addresses if (address == null) { log(sm.getString("httpConnector.allAddresses")); try { return (factory.createSocket(port, acceptCount)); } catch (BindException be) { throw new BindException(be.getMessage() + ":" + port); } } // Open a server socket on the specified address try { InetAddress is = InetAddress.getByName(address); log(sm.getString("httpConnector.anAddress", address)); try { return (factory.createSocket(port, acceptCount, is)); } catch (BindException be) { throw new BindException(be.getMessage() + ":" + address + ":" + port); } } catch (Exception e) { log(sm.getString("httpConnector.noAddress", address)); try { return (factory.createSocket(port, acceptCount)); } catch (BindException be) { throw new BindException(be.getMessage() + ":" + port); } } }
上面的ServerSocketFactory factory = getFactory()显然是创建ServerSocket实例的工厂，方法如下
/** * Return the server socket factory used by this Container. */ public ServerSocketFactory getFactory() { if (this.factory == null) { synchronized (this) { this.factory = new DefaultServerSocketFactory(); } } return (this.factory); }
工厂类DefaultServerSocketFactory实现了ServerSocketFactory接口
public final class DefaultServerSocketFactory implements ServerSocketFactory { public ServerSocket createSocket (int port) throws IOException, KeyStoreException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException, KeyManagementException { return (new ServerSocket(port)); } public ServerSocket createSocket (int port, int backlog) throws IOException, KeyStoreException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException, KeyManagementException { return (new ServerSocket(port, backlog)); } public ServerSocket createSocket (int port, int backlog, InetAddress ifAddress) throws IOException, KeyStoreException, NoSuchAlgorithmException, CertificateException, UnrecoverableKeyException, KeyManagementException { return (new ServerSocket(port, backlog, ifAddress)); } }
下面接着分析用于生命周期的start()方法
/** * Begin processing requests via this Connector. * * @exception LifecycleException if a fatal startup error occurs */ public void start() throws LifecycleException { // Validate and update our current state if (started) throw new LifecycleException (sm.getString("httpConnector.alreadyStarted")); threadName = "HttpConnector[" + port + "]"; lifecycle.fireLifecycleEvent(START_EVENT, null); started = true; // Start our background thread threadStart(); // Create the specified minimum number of processors while (curProcessors < minProcessors) { if ((maxProcessors > 0) && (curProcessors >= maxProcessors)) break; HttpProcessor processor = newProcessor(); recycle(processor); } }
首先是启动HttpConnector连接器线程，然后是初始化最少数量的HttpProcessor处理器入栈
/** * Start the background processing thread. */ private void threadStart() { log(sm.getString("httpConnector.starting")); thread = new Thread(this, threadName); thread.setDaemon(true); thread.start(); }
由于HttpConnector连接器实现了java.lang.Runnable接口，我们分析它的run()方法实现
/** * The background thread that listens for incoming TCP/IP connections and * hands them off to an appropriate processor. */ public void run() { // Loop until we receive a shutdown command while (!stopped) { // Accept the next incoming connection from the server socket Socket socket = null; try { // if (debug >= 3) // log("run: Waiting on serverSocket.accept()"); socket = serverSocket.accept(); // if (debug >= 3) // log("run: Returned from serverSocket.accept()"); if (connectionTimeout > 0) socket.setSoTimeout(connectionTimeout); socket.setTcpNoDelay(tcpNoDelay); } catch (AccessControlException ace) { log("socket accept security exception", ace); continue; } catch (IOException e) { // if (debug >= 3) // log("run: Accept returned IOException", e); try { // If reopening fails, exit synchronized (threadSync) { if (started && !stopped) log("accept error: ", e); if (!stopped) { // if (debug >= 3) // log("run: Closing server socket"); serverSocket.close(); // if (debug >= 3) // log("run: Reopening server socket"); serverSocket = open(); } } // if (debug >= 3) // log("run: IOException processing completed"); } catch (IOException ioe) { log("socket reopen, io problem: ", ioe); break; } catch (KeyStoreException kse) { log("socket reopen, keystore problem: ", kse); break; } catch (NoSuchAlgorithmException nsae) { log("socket reopen, keystore algorithm problem: ", nsae); break; } catch (CertificateException ce) { log("socket reopen, certificate problem: ", ce); break; } catch (UnrecoverableKeyException uke) { log("socket reopen, unrecoverable key: ", uke); break; } catch (KeyManagementException kme) { log("socket reopen, key management problem: ", kme); break; } continue; } // Hand this socket off to an appropriate processor HttpProcessor processor = createProcessor(); if (processor == null) { try { log(sm.getString("httpConnector.noProcessor")); socket.close(); } catch (IOException e) { ; } continue; } // if (debug >= 3) // log("run: Assigning socket to processor " + processor); processor.assign(socket); // The processor will recycle itself when it finishes } // Notify the threadStop() method that we have shut ourselves down // if (debug >= 3) // log("run: Notifying threadStop() that we have shut down"); synchronized (threadSync) { threadSync.notifyAll(); } }
上面方法中，监听客户端的http请求，当监听到http请求时，获取Socket实例，然后委派给HttpProcessor对象进行处理（处理器线程吧），最后是如果收到停止连接器线程命令， 则事件通知可以停止线程了
在上面我们还没有来得及分析HttpProcessor对象的初始化相关，所以要重新回到start()方法（源码分析有时要跟踪方法中对多个其他方法的调用，深度优先则顾此失彼，难以兼顾；而广度优先则不便纵向深入）
// Create the specified minimum number of processors while (curProcessors < minProcessors) { if ((maxProcessors > 0) && (curProcessors >= maxProcessors)) break; HttpProcessor processor = newProcessor(); recycle(processor); }
这里是创建最少数量的HttpProcessor处理器并入栈，我们先分析newProcessor()方法的实现
/** * Create and return a new processor suitable for processing HTTP * requests and returning the corresponding responses. */ private HttpProcessor newProcessor() { // if (debug >= 2) // log("newProcessor: Creating new processor"); HttpProcessor processor = new HttpProcessor(this, curProcessors++); if (processor instanceof Lifecycle) { try { ((Lifecycle) processor).start(); } catch (LifecycleException e) { log("newProcessor", e); return (null); } } created.addElement(processor); return (processor); }
我们可以看到，这里主要是实例化HttpProcessor对象，传入HttpConnector实例本身（里面要用到HttpConnector对象的创建Request对象方法和创建Response对象方法），然后向上转型为Lifecycle接口类型，并调用它的start()方法，接着Vector created = new Vector()成员变量添加该HttpProcessor对象（Vector实现List接口，内部采用数组实现，其操作方法支持线程同步），最后返回实例
/** * Recycle the specified Processor so that it can be used again. * * @param processor The processor to be recycled */ void recycle(HttpProcessor processor) { // if (debug >= 2) // log("recycle: Recycling processor " + processor); processors.push(processor); }
这里将HttpProcessor对象入栈，成员变量Stack processors = new Stack()继承自Vector，是一种先进后出的数据结构
我们现在来分析run()方法里面的相关源码，也许更容易理解
/** * Create (or allocate) and return an available processor for use in * processing a specific HTTP request, if possible. If the maximum * allowed processors have already been created and are in use, return * <code>null</code> instead. */ private HttpProcessor createProcessor() { synchronized (processors) { if (processors.size() > 0) { // if (debug >= 2) // log("createProcessor: Reusing existing processor"); return ((HttpProcessor) processors.pop()); } if ((maxProcessors > 0) && (curProcessors < maxProcessors)) { // if (debug >= 2) // log("createProcessor: Creating new processor"); return (newProcessor()); } else { if (maxProcessors < 0) { // if (debug >= 2) // log("createProcessor: Creating new processor"); return (newProcessor()); } else { // if (debug >= 2) // log("createProcessor: Cannot create new processor"); return (null); } } } }
这里是从Stack processors = new Stack()成员变量里面获取HttpProcessor对象 ，后面的代码不用多加解释了吧，你懂的！
后面那段代码是干嘛的
// Notify the threadStop() method that we have shut ourselves down // if (debug >= 3) // log("run: Notifying threadStop() that we have shut down"); synchronized (threadSync) { threadSync.notifyAll(); }
我们看到threadStop()方法里面的代码，可以看出上面的代码块是用来通知线程停止的
/** * Stop the background processing thread. */ private void threadStop() { log(sm.getString("httpConnector.stopping")); stopped = true; try { threadSync.wait(5000); } catch (InterruptedException e) { ; } thread = null; }
由于HttpProcessor处理器类的源码分析相对独立，加上篇幅还比较多，因此本文先到这里，下文继续……
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