dwr comet 方式实现不用前台请求，后台直接精确推送消息

最新推荐文章于 2020-03-01 23:19:07 发布

最新推荐文章于 2020-03-01 23:19:07 发布 · 151 阅读

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#dwr comet 后台消息精确推送

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本文详细介绍了一种使用DWR实现客户端与服务器双向通信的方法，包括DWR的配置、消息监听器的实现、消息实体定义等内容。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

突然发现我出书的可能性太小了，写了几篇小博文直接就是代码，没有啥文字修饰，好吧，

综合从网上看的资料，得出以下总结。

step.1 首先下载 dwr.jar 并在 web.xml 中整合 DWR 及添加用户登入、登出监听器

<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>activeReverseAjaxEnabled</param-name>

<param-value>true</param-value>

</init-param>

<init-param>

<param-name>pollAndCometEnabled</param-name>

<param-value>true</param-value>

</init-param>

<load-on-startup>1</load-on-startup>

</servlet>

<servlet-mapping>

<servlet-name>dwr-invoker</servlet-name>

<url-pattern>/dwr/*</url-pattern>

</servlet-mapping>

<servlet>

<servlet-name>initScriptSessionListener</servlet-name>

<servlet-class>

com.success.platform.component.messages.init.InitScriptSession

</servlet-class>

<load-on-startup>1</load-on-startup>

</servlet>

step.2

· 建立 dwr.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN" "http://www.getahead.ltd.uk/dwr/dwr30.dtd">

<dwr>

<allow>

</create>

</allow>

</dwr>

1. javascript="DwrHelper" web 页内引用的 JS 文件名 .

2. name="beanName" value="messageHelper" spring 中 beanName

step.3

· 建立 InitScriptSession.java

· 用户登入、登出监听器

public class InitScriptSession extends GenericServlet {

/**

private static final long serialVersionUID = 1L;

private static final Logger logger = Logger.getLogger(InitScriptSession.class);

ServletContext application;

public void init() {

Container container = ServerContextFactory.get().getContainer();

ScriptSessionManager manager = container.getBean(ScriptSessionManager.class);

ScriptSessionListener listener = new ScriptSessionListener() {

public void sessionCreated(ScriptSessionEvent ev) {

try {

HttpSession session = WebContextFactory.get().getSession();

ScriptSession scriptSession = ev.getSession();

String userId = session.getAttribute("userId").toString();

scriptSession.setAttribute("userId", userId);

logger.info("add " + scriptSession.getId()+ ", put userid into scriptSession");

} catch (Exception e) {

logger.warn(" 会话失效 ");

}

public void sessionDestroyed(ScriptSessionEvent ev) {

ev.getSession().removeAttribute("userId");

logger.info("destroy ScriptSession: " + ev.getSession().getId());

}

};

manager.addScriptSessionListener(listener);

}

public void service(ServletRequest req, ServletResponse res) {

init();

}

step.4

· MessageEvent.java

· 消息监听

public class MessageEvent extends ApplicationEvent {

/**

private static final long serialVersionUID = 9103980818480475235L;

public MessageEvent(Object source) {

super(source);

}

step.5

· Message.java 消息实体

public class Message {

private String receiverId;// 接收人

private String sender; // 发送人

private String content; // 内容

private Date sendTime; // 发送时间

public Message(String receiverId, String sender, String content) {

super();

this.receiverId = receiverId;

this.sender = sender;

this.content = content;

}

public String getSendTime() {

String sdate="";

try {

if(null == sendTime)sendTime=DateUtil.currentDate();

sdate=DateUtil.dateToSting(sendTime);

} catch (Exception e) {

}

return sdate;

}

public void setSendTime(Date sendTime) {

this.sendTime = sendTime;

}

public String getReceiverId() {

return receiverId;

}

public void setReceiverId(String receiverId) {

this.receiverId = receiverId;

}

public String getSender() {

return sender;

}

public void setSender(String sender) {

this.sender = sender;

}

public String getContent() {

return content;

}

public void setContent(String content) {

this.content = content;

}

step.6

MessageHelper.java 消息助手

@Service("messageHelper") // 要和 dwr.xml 的 beanName 保持一致

@Scope("singleton")

public class MessageHelper implements ApplicationContextAware {

private static ApplicationContext applicationContext;

public void setApplicationContext(ApplicationContext ctx) {

MessageHelper.applicationContext = ctx;

}

public static void sendMessage(Message mes){

if(applicationContext != null){

applicationContext.publishEvent(new MessageEvent(mes));

}

step.7

NotifyClient.java 消息监听器

package com.success.platform.component.messages;

import java.util.Collection;
import org.directwebremoting.Browser;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ScriptSessionFilter;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Service;
import com.success.platform.util.WebConfig;

@Service
public class NotifyClient implements ApplicationListener<MessageEvent> {
	
	public void onApplicationEvent(MessageEvent event) {
		if (event instanceof MessageEvent) {
			send((Message) event.getSource());
		}
	}

	private void send(final Message msg) {
		
		Browser.withAllSessionsFiltered(new ScriptSessionFilter() {
			
			public boolean match(ScriptSession session) {
				 
				if (session.getAttribute("UserId") == null)
					return false;
				else 
					return (session.getAttribute("UserId"
)).equals(msg.getReceiverId());
			}
		}, new Runnable() {
			public void run() {
				Collection<ScriptSession> colls = Browser.getTargetSessions();
				for (ScriptSession scriptSession : colls) {
					scriptSession.addScript(initFunctionCall("showMessage",  msg.getContent(),msg.getSender(),msg.getSendTime()));
				}
			}
		});
	}
	
	private ScriptBuffer initFunctionCall(String funcName, Object... params) {
		ScriptBuffer script = new ScriptBuffer();
		script.appendCall(funcName, params);
		return script;
	}
}

step.8

index.jsp
这个页面，最好是个frameset 的主页面

<%@ page contentType="text/html; charset=UTF-8"%> <%@taglib prefix="s" uri="/struts-tags"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=GB18030"> <title>DWR's HelloWorld</title> <script type='text/javascript' src='${path}/dwr/engine.js'></script> <script type='text/javascript' src='${path}/dwr/util.js'></script> <script type='text/javascript' src='${path}/scripts/common/MessageHelper.js'></script> <script type='text/javascript'> window.onload=activeReverseAjax; function activeReverseAjax(){ dwr.engine.setActiveReverseAjax(true); dwr.engine.setNotifyServerOnPageUnload(true);//页面销毁或刷新时销毁当前ScriptSession dwr.engine.setErrorHandler(null); } function showMessage(content,sender,sendtime) { $.messager.show({ title:sender + ' ' +sendtime, msg:content, timeout:0, showType:'slide' }); } </script> </head> <body> </body> </html>

step.9

测试的话，可在运行后台 servie 调用

MessageHelper.sendMessage(new Message("消息发送人的ID，对应Session内的userId","系统消息", "你好触摸不到的狂野怎么样收到信息了吗？。" ));