DWR实现服务器端向客户端推送消息
1.简介
DWR（Direct Web Remoting）是一个用于改善web页面与Java类交互的远程服务器端Ajax开源框架，可以帮助开发人员开发包含AJAX技术的网站。它可以允许在浏览器里的代码使用运行在WEB服务器上的JAVA函数，就像它就在浏览器里一样。
它包含两个主要的部分:允许 JavaScript从 WEB服务器上一个遵循了 AJAX原则的 Servlet中获取数据.另外一方面一个JavaScript库可以帮助 网站开发人员轻松地利用获取的数据来动态改变网页的内容.
DWR采取了一个类似AJAX的新方法来动态生成基于JAVA类的JavaScript代码。这样WEB开发人员就可以在JavaScript里使用Java代码，就像它们是 浏览器的 本地代码( 客户端代码)一样；但是Java代码运行在WEB服务器端而且可以自由访问WEB 服务器的资源。出于安全的理由，WEB开发者必须适当地配置哪些Java类可以安全的被外部使用。
[1]
这个从JAVA到JavaScript的远程功能方法给DWR的用户带来非常像传统的RPC机制,就像RMI或者SOAP一样,而且拥有运行在WEB上但是不需要 浏览器插件的好处.
DWR不认为浏览器/WEB服务器协议是重要的,而更乐于保证 编程界面的简单自然.对此最大的挑战就是把AJAX的异步特性和正常JAVA方法调用的同步特性相结合.在异步模式下,结果数据在开始调用之后的一段时间之后才可以被异步访问获取到.DWR允许WEB开发人员传递一个 回调函数,来 异步处理Java 函数调用过程.
以上是百度百科中copy的废话,下面来看步骤
2.前提条件:
2.1 dwr.jar 此包可以到官网下载:http://directwebremoting.org/dwr/downloads/index.htm(必须)
2.2 commons-logging-xxxx.jar(官网说需要)
3.eclipse中new >> Dynamic Web Project 复制dwr.jar到lib目录下会自动build path
4.打开web.xml编辑:
<?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_2_5.xsd" id="WebApp_ID" version="2.5"> <display-name>dwrDemo</display-name> <welcome-file-list> <welcome-file>login.jsp</welcome-file> <welcome-file>index.jsp</welcome-file> </welcome-file-list> <servlet> <display-name>LoginServlet</display-name> <servlet-name>LoginServlet</servlet-name> <servlet-class>com.yun.study.servlet.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/loginServlet</url-pattern> </servlet-mapping> <servlet> <servlet-name>dwr-invoker</servlet-name> <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class> <init-param> <param-name>crossDomainSessionSecurity</param-name> <param-value>false</param-value> </init-param> <init-param> <param-name>allowScriptTagRemoting</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>classes</param-name> <param-value>java.lang.Object</param-value> </init-param> <init-param> <param-name>activeReverseAjaxEnabled</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>initApplicationScopeCreatorsAtStartup</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>maxWaitAfterWrite</param-name> <param-value>3000</param-value> </init-param> <init-param> <param-name>debug</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>logLevel</param-name> <param-value>WARN</param-value> </init-param> </servlet>
<!--此处必须要有 不然前端js不能自动引入-->
<servlet-mapping>
<servlet-name>dwr-invoker</servlet-name>
<url-pattern>/dwr/*</url-pattern>
</servlet-mapping>
</web-app>以上具体的 init-param可以到官网查查文档什么的搞定
5.在web.xml同级目录下新建一个文件 dwr.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN" "http://getahead.org/dwr/dwr30.dtd"> <dwr> <allow> <create creator="new" javascript="MessagePush"> <param name="class" value="com.yun.study.service.MessagePush" /> </create> <create creator="new" javascript="TestPush"> <param name="class" value="com.yun.study.service.Test" /> </create> </allow> </dwr>以上可以看出 我的class有两个
com.yun.study.service.MessagePush
com.yun.study.service.Test属性javascript的值表示是在js中用到该类的时候引用的名字
6.新建的java类如下:
bean:
package com.yun.study.model;
public class User {
private String userId;
public String getUserId() {
return userId;
}
public void setUserId(String userId) {
this.userId = userId;
}
}
package com.yun.study.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpSession;
import org.directwebremoting.Container;
import org.directwebremoting.ServerContextFactory;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.event.ScriptSessionEvent;
import org.directwebremoting.event.ScriptSessionListener;
import org.directwebremoting.extend.ScriptSessionManager;
import org.directwebremoting.servlet.DwrServlet;
import com.yun.study.model.User;
public class DwrScriptSessionManagerUtil extends DwrServlet {
private static final long serialVersionUID = 109326676726848212L;
public void init() throws ServletException {
try {
Container container = ServerContextFactory.get().getContainer();
ScriptSessionManager manager = container
.getBean(ScriptSessionManager.class);
ScriptSessionListener listener = new ScriptSessionListener() {
public void sessionCreated(ScriptSessionEvent ev) {
HttpSession session = WebContextFactory.get().getSession();
String userId = ((User) session.getAttribute("userinfo"))
.getUserId() + "";
System.out.println("======>>>a ScriptSession is created,userId="+userId);
ev.getSession().setAttribute("userId", userId);
}
public void sessionDestroyed(ScriptSessionEvent ev) {
String userId = (String) ev.getSession().getAttribute("userId");
System.out.println("======>>>userId="+userId+" ScriptSession is distroyed");
}
};
manager.addScriptSessionListener(listener);
} catch (Exception e) {
e.printStackTrace();
}
}
}
package com.yun.study.service;
import javax.servlet.ServletException;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.WebContextFactory;
import com.yun.study.servlet.DwrScriptSessionManagerUtil;
public class MessagePush {
public void onPageLoad(String userId) {
System.out.println("=====>>>>MessagePush onPageLoad invoke begin!");
ScriptSession scriptSession = WebContextFactory.get().getScriptSession();
scriptSession.setAttribute("userId", userId);
DwrScriptSessionManagerUtil dwrScriptSessionManagerUtil = new DwrScriptSessionManagerUtil();
try {
dwrScriptSessionManagerUtil.init();
System.out.println("=====>>>>MessagePush onPageLoad invoke end!");
} catch (ServletException e) {
e.printStackTrace();
}
}
}
package com.yun.study.service;
import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.Date;
import org.directwebremoting.Browser;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ScriptSessionFilter;
public class Test {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
public void sendMessageAuto(String userid) {
System.out.println("======>>>sendMessageAuto invoke begin!");
final String userId = userid;
final String sendMessage = "长江长江,我是黄河,收到请回答!当前时间是:"+sdf.format(new Date());
Browser.withAllSessionsFiltered(new ScriptSessionFilter() {
public boolean match(ScriptSession session) {
if (session.getAttribute("userId") == null)
return false;
else
return (session.getAttribute("userId")).equals(userId);
}
}, new Runnable() {
private ScriptBuffer script = new ScriptBuffer();
public void run() {
System.out.println("====>>>invoke client browser task run.......");
script.appendCall("showMessage", sendMessage);
Collection<ScriptSession> sessions = Browser.getTargetSessions();
for (ScriptSession scriptSession : sessions) {
System.out.println("===>>>loop execute sessions userId:"+scriptSession.getAttribute("userId"));
scriptSession.addScript(script);
}
}
});
System.out.println("======>>>sendMessageAuto invoke end!");
}
}
package com.yun.study.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.yun.study.model.User;
/**
* Servlet implementation class ServerPushMessageServlet
*/
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public LoginServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String pageName = request.getParameter("pageName");
String sessionId = request.getSession().getId();
User u = new User();
u.setUserId(sessionId);
request.getSession().setAttribute("userinfo", u);
response.sendRedirect(pageName);
}
}
以下是界面:
登录:login.jsp
<?xml version="1.0" encoding="UTF-8" ?> <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/"; %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <base href="<%=basePath%>"></base> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>dwr test</title> </head> <body> <form action="<%=basePath%>/loginServlet" method="post"> <p>请点击以下button 将会模拟登录得到一个sessionKey设置到你的session中用于表示您的身份,</p> <p style="color: red;">界面将跳转到一个客户端页面(用于接收服务器推送消息的)!</p> <br/><input type="hidden" name="pageName" value="index.jsp"/> <input type="submit" value="跳转到客户端"/> </form> <br/><br/><br/> <hr/> <form action="<%=basePath%>/loginServlet" method="post"> <p>请点击以下button 将会模拟登录得到一个sessionKey设置到你的session中用于表示您的身份,</p> <p style="color: red;">界面将跳转到一个触发服务端推送消息的界面(用于通知服务器推送消息给客户端的)!</p><br/> <input type="hidden" name="pageName" value="clientPush.jsp"/> <input type="submit" value="跳转到通知服务发送界面"/> </form> </body> </html>
:index.jsp:
<?xml version="1.0" encoding="UTF-8" ?>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<base href="<%=basePath%>"></base>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>dwr client test</title>
<script type="text/javascript" src="<%=basePath%>/js/jquery-1.7.2.min.js"></script>
<script type="text/javascript" src="dwr/engine.js"></script>
<script type="text/javascript" src="dwr/util.js"></script>
<script type="text/javascript"
src="<%=basePath%>/dwr/interface/MessagePush.js"></script>
<script type="text/javascript">
//通过该方法与后台交互，确保推送时能找到指定用户
function onPageLoad() {
var userId = '${userinfo.userId}';
MessagePush.onPageLoad(userId);
}
//服务器向客户端推送信息的方法
function showMessage(autoMessage) {
$("#serverSay").html(autoMessage);
}
</script>
</head>
<body
onload="onPageLoad();dwr.engine.setActiveReverseAjax(true);dwr.engine.setNotifyServerOnPageUnload(true);;">
This is my DWR DEOM page.please copy this userId <span style="color: red;">${userinfo.userId}</span>
to clientPush.jsp page to trigger a event,server will send message to client......
<hr/><br/>
<div id="DemoDiv">demo</div>
<h2 style="color: red;" id="serverSay"></h2>
</body>
</html>
clientPush.jsp:
<?xml version="1.0" encoding="UTF-8" ?>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<base href="<%=basePath%>"></base>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>server push message trigger</title>
<script type="text/javascript" src="<%=basePath%>/js/jquery-1.7.2.min.js"></script>
<script type='text/javascript' src='dwr/engine.js'></script>
<script type='text/javascript' src='dwr/util.js'></script>
<script type='text/javascript' src='dwr/interface/TestPush.js'></script>
<script type="text/javascript">
function test() {
var userId = $("#userId").val();
TestPush.sendMessageAuto(userId);
}
</script>
</head>
<body>
client userId <input type="text" name="userId" id="userId" />
<br />
<input type="button" value="Send" onclick="test()" />
</body>
</html>
ok!
注意:以上测试 客户端和通知服务端的页面请使用两个不同的浏览器测试,以免session存在覆盖的问题
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