[置顶] springmvc实现long-pulling技术
背景介绍：
项目中有一个通讯模块，本来是用websocket全双工技术实现的，但IE10以下不支持websocket，而国内的360、2345浏
览器封装的全部是IE10以下的内核，考虑到网站在国内的客户，不得不在不支持websocket时候也要提供通讯支持，于
是决定在不支持websocket的浏览器上用long-pulling技术替代。
可行性分析：
Servlet 3.0已经开始支持async，Spring MVC 3.2也开始对异步提供支持，于是结合DeferredResult来实现聊天技术。
具体实现：
1 文件配置：
假设你已经有了spring+springmvc框架，我们只需对配置文件做微小改动，要在web.xml中的所有的filter及servlet中需要声明使用async：
<async-supported>true</async-supported>web.xml完整配置如下：
<?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" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0"> <!-- 配置spring-mybatis.xml --> <context-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring-mybatis.xml</param-value> </context-param> <filter> <filter-name>encodingFilter</filter-name> <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class> <async-supported>true</async-supported> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>encodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!-- 配置spring-mvc --> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <listener> <listener-class>org.springframework.web.util.IntrospectorCleanupListener</listener-class> </listener> <servlet> <servlet-name>SpringMVC</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring-mvc.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> <async-supported>true</async-supported> </servlet> <servlet-mapping> <servlet-name>SpringMVC</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>文件配置搞定。
2 建立控制器Controller
/**
* @作者 yyp
* @文件名 ChatController.java
* @作用 处理聊天消息
* @Blog http://blog.csdn.net/gisredevelopment
*/
@Controller
public class ChatController {
//存放所有的用户请求
private final Map<String, DeferredResult<Message>> chatRequests = new ConcurrentHashMap<String, DeferredResult<Message>>();
//时间格式化
private final SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
/**
* @作者 yyp
* @作用 登录
* @param name 用户名
* @param session 会话
* @return 聊天室页面
*/
@RequestMapping(value = "/login", method = RequestMethod.POST)
public String login(@RequestParam String name, HttpSession session){
session.setAttribute("user", name);
Message msg = new Message();
msg.setUser("系统");
msg.setDate(sdf.format(new Date()));
msg.setContent(name + "已加入");
//通知所有用户有人进入聊天室
processMessage(msg);
return "room";
}
/**
*
* @作者 yyp
* @作用 读取最新消息
* @param session 会话
* @return DeferredResult<Message>
*/
@RequestMapping(value = "/getMessages", method = RequestMethod.GET)
@ResponseBody
public DeferredResult<Message> getMessages(HttpSession session){
//取出当前登录用户
final String user = (String)session.getAttribute("user");
//创建DeferredResult<Message>
DeferredResult<Message> dr = new DeferredResult<Message>();
//若用户不存在则直接返回，否则将其放入用户请求列表中然后返回
if(null == user){
return dr;
}else{
//当DeferredResult对客户端响应后将其从列表中移除
dr.onCompletion(new Runnable() {
@Override
public void run() {
// TODO 自动生成的方法存根
chatRequests.remove(user);
}
});
chatRequests.put(user, dr);
return dr;
}
}
/**
* @作者 yyp
* @作用 接收客户端消息
* @param session 会话
* @param content 消息内容
* @return Map<String, String>
*/
@RequestMapping(value = "/setMessage", method = RequestMethod.POST)
@ResponseBody
public Map<String, String> setMessage(HttpSession session, @RequestParam String content){
Message msg = new Message();
msg.setContent(content);
msg.setDate(sdf.format(new Date()));
msg.setUser((String)session.getAttribute("user"));
//发布消息给所有用户
processMessage(msg);
Map<String, String> map = new HashMap<String, String>(1);
map.put("success", "true");
return map;
}
/**
* @作者 yyp
* @作用 退出聊天室
* @param session 会话
* @return Map<String, String>
*/
@RequestMapping(value = "/logout", method = RequestMethod.GET)
@ResponseBody
public Map<String, String> logout(HttpSession session){
Message msg = new Message();
String user = (String)session.getAttribute("user");
msg.setContent("已离开");
msg.setDate(sdf.format(new Date()));
msg.setUser(user);
chatRequests.remove(user);
//通知所有用户有人离开聊天室
processMessage(msg);
Map<String, String> map = new HashMap<String, String>(1);
map.put("success", "true");
return map;
}
/**
* @作者 yyp
* @作用 将消息信息发布给所有在线用户
* @param msg 消息
*/
private void processMessage(Message msg){
Set<String> keys = chatRequests.keySet();
for(String key : keys){
chatRequests.get(key).setResult(msg);
}
}
}
3 建立消息实体
/**
* @作者 yyp
* @文件名 Message.java
* @作用 封装用户的聊天内容
* @Blog http://blog.csdn.net/gisredevelopment
*/
public class Message {
private String user;
private String date;
private String content;
}
4 页面代码-登录
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录</title>
</head>
<body>
<form action="login" method="post">
name: <input type="text" name="name"/>
<input value="登录" type="submit"/>
</form>
</body>
</html>
5 页面代码-聊天
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<% String user =(String)session.getAttribute("user"); %>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>聊天室</title>
<script type="text/javascript" src="/imgr?src=http%3A%2F%2Fwww.ineeke.com%2Farchives%2F1486%2Fjquery-1.10.1.min.js"></script>
<script type="text/javascript">
$(function(){
(function getMessages(){
$.ajax({
dataType: "json",
url: 'getMessages',
cache: false,
success: function(data){
var v = $('#text').val();
v += '\r\n' + data.date + ' ' + data.user + '：' + data.content;
$('#text').val(v);
}
}).always(function(){
getMessages();
});
})();
$('#form').submit(function(event){
event.preventDefault();
var values = $(this).serialize();
$.post('setMessage', values, function(data){
$('#form>[name=content]').val('');
}, 'json');
});
$('#logout').click(function(){
$.ajax({
dataType: "json",
url: 'logout',
cache: false,
success: function(data){
window.location.href = 'index.jsp';
}
});
});
});
</script>
</head>
<body>
欢迎：<%=user %><br/>
<textarea id="text" rows="20" style="width: 500;"></textarea>
<form id="form" action="sendMessage" method="post">
<input type="text" name="content" />
<input value="发送" type="submit"/>
<input id="logout" value="离开" type="button"/>
</form>
</body>
</html>