Tomcat comet 服務器推技術介紹

jopen 12年前發布 | 86K 次閱讀 Tomcat 應用服務器

Tomcat已經實現了自己的comet方式，并且提供了一個例子。這樣網上的例子很多，我精簡了些。

MessageSender.java

package me.comet;


import java.io.IOException;
import java.io.OutputStream;
import java.util.Date;


import javax.servlet.ServletResponse;


public class MessageSender extends Thread {



private ServletResponse connection;

public MessageSender(ServletResponse connection) {
    this.connection = connection;
}

public void run() {
    try {
        while (true) {
            if (connection == null) {
                synchronized (this) {
                    wait();
                }
            }

            OutputStream out = connection.getOutputStream();
            out.write(getString().getBytes());
            out.flush();
            connection.flushBuffer();

            System.out.print(getString());

            Thread.sleep(1000);
        }
    } catch (IOException e) {
        e.printStackTrace();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

@SuppressWarnings("deprecation")
private String getString() {
    return Thread.currentThread()+" CurrentTime "+new Date().toLocaleString() + "\n";
}




}</pre> 
  
 
  
TimeServlet.java
 
  
package me.comet;


import java.io.IOException;


import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


import org.apache.catalina.CometEvent;
import org.apache.catalina.CometProcessor;


public class TimeServlet extends HttpServlet implements CometProcessor {
    private static final long serialVersionUID = 1L;
    private static final Integer TIMEOUT = 10 * 1000;



private MessageSender sender = null;

public void event(CometEvent event) throws IOException, ServletException {

    HttpServletRequest request = event.getHttpServletRequest();
    HttpServletResponse response = event.getHttpServletResponse();

    if (event.getEventType() == CometEvent.EventType.BEGIN) {
        log("Begin for session: " + request.getSession(true).getId());
        request.setAttribute("org.apache.tomcat.comet.timeout", TIMEOUT);

        sender = new MessageSender(response);
        sender.start();

    } else if (event.getEventType() == CometEvent.EventType.ERROR) {
        log("Error for session: " + request.getSession(true).getId());
        event.close();
    } else if (event.getEventType() == CometEvent.EventType.END) {
        log("End for session: " + request.getSession(true).getId());
        event.close();
    } else if (event.getEventType() == CometEvent.EventType.READ) {
        throw new UnsupportedOperationException("This servlet does not accept data");
    }
}

@Override
public void destroy() {
    sender.interrupt();
    sender = null;
}



}</pre> 
  
web.xml
 
  
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee&quot;
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance&quot;
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"&gt;



<welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
</welcome-file-list>

<servlet>
    <servlet-name>TimeServlet</servlet-name>

    <servlet-class>me.comet.TimeServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>TimeServlet</servlet-name>

    <url-pattern>/time</url-pattern>
</servlet-mapping>




</web-app></pre> 
  
 
  
test.jsp
 
  
<%@page contentType="text/html" pageEncoding="UTF-8"%>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"&gt;
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>Comet Weather</title>
    </head>



<body>
    <label>記錄</label>
    <br/>
    <iframe src="http://localhost:8080/comet/time"
        width="60%" height="300" frameborder="1"></iframe>
</body>




</html></pre> 
  
 
  
更改 tomcat/conf/server.xml
 
  
<Connector port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol"  connectionTimeout="20000" redirectPort="8443" />
 
  
 
  
更改 tomcat/conf/context.xml
 
  
<Context>
    <Loader delegate="true" />



    <WatchedResource>WEB-INF/web.xml</WatchedResource>



</Context></pre> 
  
 
  
jar包
 
  
添加tomcat/lib/catalina.jar
 
  
 
  
測試地址：http://localhost:8080/comet/test.jsp 
 來自：http://zkeshun.iteye.com/blog/1391922
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