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Tomcat体系结构中有一个非常重要的概念——连接器，看下面这张图
一个connecotr对应一个container，connector用于接收请求，然后传递给container组件去处理，tomcat中默认的连接器是coyote，按照协议类型分，有http和ajp的连接器。
HTTP/1.1协议负责建立HTTP连接，web应用通过浏览器访问tomcat服务器用的就是这个连接器，默认监听的是8080端口；
AJP/1.3协议负责和其他HTTP服务器建立连接，监听的是8009端口，比如tomcat和apache或者iis集成时需要用到这个连接器。
下面是一个简单的connector实现：
package server2.connector;import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
/*** HttpConnector主要负责接入消息，分发给不同的处理器* * @author Administrator**/
public class HttpConnector implements Runnable{private boolean shutdown = false;// 服务器是否停止private String scheme = "http";public String getScheme() {return scheme;}public void setScheme(String scheme) {this.scheme = scheme;}@Overridepublic void run() {ServerSocket serverSocket = null;int port = 8080;try {serverSocket = new ServerSocket(port, 1,InetAddress.getByName("127.0.0.1"));} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}Socket socket = null;while (!shutdown) {// 不停的接受请求try {socket = serverSocket.accept();} catch (IOException e) {e.printStackTrace();}HttpProcessor processor = new HttpProcessor();processor.process(socket);}}/*** 启动connector监听线程*/public void start(){System.out.println("started!!!");Thread thread = new Thread(this);thread.start();}
}
异步方式的connector它的run方法如下：
/*** 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 commandwhile (!stopped) {// Accept the next incoming connection from the server socketSocket socket = null;try {// if (debug >= 3)// log("run: Waiting on serverSocket.accept()");//接收客户端的socket连接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, exitsynchronized (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//创建processor，如果连接池没有可用的处理器，则拒绝消息，其中的createProcessor方法基于栈来实现的处理池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);//否则的话将socket传递给processorprocessor.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();}}
/*** The background thread that listens for incoming TCP/IP connections and* hands them off to an appropriate processor.*/public void run() {// Process requests until we receive a shutdown signal//不停的循环处理消息while (!stopped) {// Wait for the next socket to be assigned//调用自身的await()Socket socket = await();//未获取到socket继续循环if (socket == null)continue;// Process the request from this sockettry {//获取到则进行处理process(socket);} catch (Throwable t) {log("process.invoke", t);}// Finish up this request//将该处理线程放回池中复用connector.recycle(this);}// Tell threadStop() we have shut ourselves down successfullysynchronized (threadSync) {threadSync.notifyAll();}}
/*** Await a newly assigned Socket from our Connector, or <code>null</code>* if we are supposed to shut down.该方法是个同步方法，并且内部可能发生阻塞*/private synchronized Socket await() {// Wait for the Connector to provide a new Socket
//如果没有可处理的socket则同步阻塞，这里connector调用processor的assign方法会传递
//过来可用的socketwhile (!available) {try {wait();} catch (InterruptedException e) {}}// Notify the Connector that we have received this Socket
//否则可以处理，成员变量赋值给私有变量Socket socket = this.socket;
//设置为没有可处理的socketavailable = false;
//唤醒被阻塞的线程notifyAll();if ((debug >= 1) && (socket != null))log(" The incoming request has been awaited");return (socket);}再来看下assign方法：
synchronized void assign(Socket socket) {// Wait for the Processor to get the previous Socket//available表示是否有可处理的socket，第一次值为false跳过while循环while (available) {//try {wait();} catch (InterruptedException e) {}}// Store the newly available Socket and notify our thread//将socket赋值给成员变量socketthis.socket = socket;//修改值为trueavailable = true;//唤醒阻塞在该对象上的线程notifyAll();if ((debug >= 1) && (socket != null))log(" An incoming request is being assigned");}
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