dwr进行消息推送示例
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<?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="PushMessage"> <param name="class" value="com.manhui.push.controller.PushMessage"/> </create> </allow> </dwr>
关于dwr的介绍可自行度娘,这里主要做一个dwr进行消息推送的demo
第一步:这里使用maven项目,先引入jar的仓库地址:
1 <dependency> 2 <groupId>org.directwebremoting</groupId> 3 <artifactId>dwr</artifactId> 4 <version>3.0.0-RELEASE</version> 5 </dependency>
第二步:web.xml配置
<!-- dwr相关配置 --> <servlet> <servlet-name>dwr-invoker</servlet-name> <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class> <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> <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>6000</param-value> </init-param> <load-on-startup>2</load-on-startup> </servlet> <servlet-mapping> <servlet-name>dwr-invoker</servlet-name> <url-pattern>/dwr/*</url-pattern> </servlet-mapping>
第三步:后台编码
package com.manhui.push.controller; import java.util.Collection; import org.apache.log4j.Logger; import org.directwebremoting.Browser; import org.directwebremoting.ScriptBuffer; import org.directwebremoting.ScriptSession; import org.directwebremoting.ScriptSessionFilter; import org.directwebremoting.WebContextFactory; /** * 推送消息控制层,这里主要是进行消息的精确推送,当然如果要进行所有推送,则不需要进行过滤处理即可 * @author hq * */ public class PushMessage { private Logger log = Logger.getLogger(PushMessage.class); // 载入页面时调用,传入name值作为推送的标识 public void onPageLoad(String name) { ScriptSession session = WebContextFactory.get().getScriptSession(); session.setAttribute("name", name); } public void addMessage(String userid, String message) { final String userId = userid; final String autoMessage = message; ScriptSession session = WebContextFactory.get().getScriptSession(); String from =(String) session.getAttribute("name"); // 获取所有scriptsession并通过ScriptSessionFilter筛选符合条件的ScriptSession Browser.withAllSessionsFiltered(new ScriptSessionFilter() { // 实现match方法,条件为真为筛选出来的session public boolean match(ScriptSession session) { String name = session.getAttribute("name").toString(); return name == null ? false : userId.equals(name); } }, new Runnable() { private ScriptBuffer script = new ScriptBuffer(); public void run() { // 设定前台接受消息的方法和参数 script.appendCall("receiveMessages", autoMessage); Collection<ScriptSession> sessions = Browser .getTargetSessions();//获取有效的scriptsession // 向所有符合条件的页面推送消息 for (ScriptSession scriptSession : sessions) { if (scriptSession.getAttribute("name").equals(userId)) { scriptSession.addScript(script); } } } }); } }
第四步:在web.xml同级目录下创建dwr.xml文件
<?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="PushMessage"> <param name="class" value="com.manhui.push.controller.PushMessage"/> </create> </allow> </dwr>
第五步:在需要推送消息的页面引入相关js,并在页面初始化之前加载相关方法
<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/PushMessage.js"></script>
<script type="text/javascript" src="dwr/interface/PushMessage.js"></script>该js文件是根据dwr.xml自行生成的,前面的是dwr.jar里面的
页面初始化加载调用:
dwr.engine.setActiveReverseAjax(true);// 开启逆向Ajax,也可写在body标签的onload方法中 dwr.engine.setNotifyServerOnPageUnload(true); dwr.engine.setErrorHandler(function(){});//" 这个方法 防止项目已经关闭,客户页面还未关闭,页面会谈Error的问题 onPageLoad();
var chatlog = ""; var name = \'${name}\'; function sendMessage() { var message = $("#message").val(); var user = $("#user").val(); // 通过代理调用后台的addMessage方法发送消息 PushMessage.addMessage(user, message); } // 前台接受消息的方法,由后台调用 function receiveMessages(messages) { var lastMessage = messages; chatlog = "<p>" + lastMessage + "</p>" + chatlog; $("#list").html(chatlog); } //读取name值作为推送的唯一标示 function onPageLoad(){ // 获取URL中的name属性为唯一标识符 var userId = name; $("#myName").html(userId); // 通过代理,传入区别本页面的唯一标识符 PushMessage.onPageLoad(userId); }
第六步:效果如下
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