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2014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：
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：
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
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 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：
<%@ 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 >
<input type="text" id="writeMsg"></input>
<input type="button" value="send" ></input>
</body>
</html>
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