Server-Sent Events实现服务端单向推送消息事件

来源：互联网发布：手机植入监控软件编辑：程序博客网时间：2024/06/07 02:31

Server-Sent Events（简称SSE）也是H5的新特性，除了IE之外，其他的主流浏览器都支持。这个技术不需要服务端的特别支持，只需要服务端输出的时候设置内容类型为text/event-stream即可。

下面是具体的代码实现（我用java实现的）。

一、jsp页面

<%@ 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>Server-Sent Events Demo</title>
<%
request.setAttribute("ctx", request.getContextPath());
%>
</head>
<body>
<h1>Server-Sent Events</h1>
<div>
<form action="">
<input onclick="startSend()" value="开启服务端消息单向推送" type="button">
<br>
</form>
</div>
<div id="output"></div>
</body>
<script type="text/javascript">
function startSend() {
if(typeof(EventSource)!=="undefined"){
var eventSource = new EventSource("${ctx}/sse");
eventSource.onmessage = function(event) {
document.getElementById('output').innerHTML+=event.data+"<br/>";
};
}else{
alert("您的浏览器版本过低，不支持SSE！");
}

}
</script>
</html>

二、Servlet处理请求

package cn.remotejob.web;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Date;
import java.util.concurrent.TimeUnit;

import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class SseServlet extends HttpServlet {

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
long start = System.currentTimeMillis();
resp.setContentType("text/event-stream");
resp.setCharacterEncoding("UTF-8");
resp.setHeader("Cache-Control", "no-cache");
resp.setHeader("Pragma","no-cache");
resp.setDateHeader("Expires",0);

PrintWriter writer = resp.getWriter();
// writer.print("retry: 10000\n"); //设置请求间隔时间
// writer.print("data: " + System.currentTimeMillis()+"\n\n");
writer.println("retry: 10000"); //设置请求间隔时间
writer.println("data: " + System.currentTimeMillis()+"\n");

writer.flush();

System.out.println("耗时======"+(System.currentTimeMillis()-start));
}

}

注意：输出的数据是有格式要求的，这里只是给出个可以跑通的例子，具体的SSE知识可以参考这篇文章 http://www.cnblogs.com/wishyouhappy/p/3733570.html

三、在web.xml配置servlet

<servlet>
<servlet-name>sse</servlet-name>
<servlet-class>cn.remotejob.web.SseServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>sse</servlet-name>
<url-pattern>/sse</url-pattern>
</servlet-mapping>

阅读全文

0 0