基于Tomcat的WebSocket
原文地址：http://redstarofsleep.iteye.com/blog/14886392014年2月更新: 此API为Tomcat私有,当时Java没有标准API,现在Java有标准API,JSR536,此API不建议使用,新的用法请参照: http://redstarofsleep.iteye.com/blog/1974620
之前大概的看过WebSocket,当时Tomcat还不支持WebSocket,所以当时写了一篇基于Jetty的WebSocket实现,地址如下:
http://redstarofsleep.iteye.com/blog/1307608
现在Tomcat7.0.27发布了，从这个版本开始Tomcat就支持WebSocket了。
Tomcat的WebSocket和Jetty的大致上差不多，大同小异，这里就简单的贴两个类吧（此例子未考虑多线程的情况）：
第一个类，这个和Jetty一样，需要一个Servlet来处理WebSocket请求：
Java代码
[*]package lhc.websocket;
[*]
[*]import org.apache.catalina.websocket.StreamInbound;
[*]import org.apache.catalina.websocket.WebSocketServlet;
[*]
[*]public class MyWebSocketServlet extends WebSocketServlet {
[*]
[*] private static final long serialVersionUID = -7178893327801338294L;
[*]
[*] @Override
[*] protected StreamInbound createWebSocketInbound(String arg0) {
[*]System.out.println("##########");
[*] return new MyMessageInbound();
[*] }
[*]
[*]}
这个Servlet继承自WebSocketServlet，实现createWebSocketInbound方法。该方法返回第二个类的实例。
第二个类，处理每一次具体的WebSocket任务：
Java代码
[*]package lhc.websocket;
[*]
[*]import java.io.IOException;
[*]import java.nio.ByteBuffer;
[*]import java.nio.CharBuffer;
[*]
[*]import lhc.init.InitServlet;
[*]
[*]import org.apache.catalina.websocket.MessageInbound;
[*]import org.apache.catalina.websocket.WsOutbound;
[*]
[*]public class MyMessageInbound extends MessageInbound {
[*]
[*] @Override
[*] protected void onBinaryMessage(ByteBuffer arg0) throws IOException {
[*] // TODO Auto-generated method stub
[*]
[*] }
[*]
[*] @Override
[*] protected void onTextMessage(CharBuffer msg) throws IOException {
[*] for (MessageInbound messageInbound : InitServlet.getSocketList()) {
[*] CharBuffer buffer = CharBuffer.wrap(msg);
[*] WsOutbound outbound = messageInbound.getWsOutbound();
[*] outbound.writeTextMessage(buffer);
[*] outbound.flush();
[*] }
[*]
[*] }
[*]
[*] @Override
[*] protected void onClose(int status) {
[*] InitServlet.getSocketList().remove(this);
[*] super.onClose(status);
[*] }
[*]
[*] @Override
[*] protected void onOpen(WsOutbound outbound) {
[*] super.onOpen(outbound);
[*] InitServlet.getSocketList().add(this);
[*] }
[*]
[*]
[*]
[*]}
这个类继承自MessageInbound类，必须实现onBinaryMessage和onTextMessage方法。Jetty中只有一个onMessage方法，而Tomcat细化成了2个方法。
还要一个初始化的Servlet
Java代码
[*]package lhc.init;
[*]
[*]import java.util.ArrayList;
[*]import java.util.List;
[*]
[*]import javax.servlet.ServletConfig;
[*]import javax.servlet.ServletException;
[*]import javax.servlet.http.HttpServlet;
[*]
[*]import org.apache.catalina.websocket.MessageInbound;
[*]
[*]public class InitServlet extends HttpServlet {
[*]
[*] private static final long serialVersionUID = -3163557381361759907L;
[*]
[*] private static List<MessageInbound> socketList;
[*]
[*] public void init(ServletConfig config) throws ServletException {
[*] InitServlet.socketList = new ArrayList<MessageInbound>();
[*] super.init(config);
[*] System.out.println("Server start============");
[*] }
[*]
[*] public static List<MessageInbound> getSocketList() {
[*] return InitServlet.socketList;
[*] }
[*]}
最后，web.xml中进行一下Servlet的配置。
Xml代码
[*]<?xml version="1.0" encoding="UTF-8"?>
[*]<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
[*] <display-name>wsoc</display-name>
[*] <welcome-file-list>
[*] <welcome-file>index.jsp</welcome-file>
[*] </welcome-file-list>
[*]
[*] <servlet>
[*] <servlet-name>mywebsocket</servlet-name>
[*] <servlet-class>lhc.websocket.MyWebSocketServlet</servlet-class>
[*] </servlet>
[*] <servlet-mapping>
[*] <servlet-name>mywebsocket</servlet-name>
[*] <url-pattern>*.do</url-pattern>
[*] </servlet-mapping>
[*]
[*] <servlet>
[*] <servlet-name>initServlet</servlet-name>
[*] <servlet-class>lhc.init.InitServlet</servlet-class>
[*] <load-on-startup>1</load-on-startup>
[*] </servlet>
[*]</web-app>
页面的话，就是标准的HTML5的websocket，这个和服务器是否是Tomcat或者Jetty是无关的：
Html代码
[*]<%@ page language="java" contentType="text/html; charset=UTF-8"
[*] pageEncoding="UTF-8"%>
[*]<!DOCTYPE html>
[*]<html>
[*]<head>
[*]<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
[*]<title>Index</title>
[*]<script type="text/javascript">
[*]var ws = null;
[*]function startWebSocket() {
[*] if ('WebSocket' in window)
[*] ws = new WebSocket("ws://localhost:8080/wsoc/mywebsocket.do");
[*] else if ('MozWebSocket' in window)
[*] ws = new MozWebSocket("ws://localhost:8080/wsoc/mywebsocket.do");
[*] else
[*] alert("not support");
[*]
[*]
[*] ws.onmessage = function(evt) {
[*] alert(evt.data);
[*] };
[*]
[*] ws.onclose = function(evt) {
[*] alert("close");
[*] };
[*]
[*] ws.onopen = function(evt) {
[*] alert("open");
[*] };
[*]}
[*]
[*]function sendMsg() {
[*] ws.send(document.getElementById('writeMsg').value);
[*]}
[*]</script>
[*]</head>
[*]<body onload="startWebSocket();">
[*]<input type="text" id="writeMsg"></input>
[*]<input type="button" value="send" onclick="sendMsg()"></input>
[*]</body>
[*]</html>
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