Dwr java伺服器反推技術（伺服器推送到頁面）
阿新 • • 發佈：2018-12-22
原始碼及展示
展示
簡介
簡略的實現了伺服器反向通知到前臺頁面, 在輸入框輸入文字，點擊發送按鈕，訊息會被通知到所有線上的使用者。
實現
依賴
- dwr.jar
- commons-logging-1.0.4.jar
- jquery-3.2.1.min.js
jar包可以直接在我gitee下載
目錄結構
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app dwr.xml
<!DOCTYPE dwr PUBLIC
"-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN"
"http://getahead.org/dwr/dwr30.dtd">
<dwr>
<allow>
<!-- javascript="Java類名" -->
<create creator="new" javascript="DwrPush">
<param name="class">util.DwrPush</param>
</create>
</allow>
</dwr>index.jsp
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%
// 用於獲取專案根目錄
String path = request.getContextPath();
String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<!-- 需要引入的dwr的三個重要js 路徑要和web.xml server-mapping內配置的路徑一致-->
<script type="text/javascript" src="<%=path%>/js/dwr/util.js"></script>
<script type="text/javascript" src="<%=path%>/js/dwr/engine.js"></script>
<script type="text/javascript"
src="<%=path%>/js/dwr/interface/DwrPush.js"></script>
<script type="text/javascript" src="<%=path%>/js/jquery-3.2.1.min.js"></script>
<title>Clannad聊天室</title>
</head>
<body>
<ul id="ul" style="color: red; font-size: 15px;"></ul>
<input type="text" name="msg" id="msg" size="30">
<input type="button" name="button" id="send" value="傳送">
</body>
<script type="text/javascript">
/* 開啟ajax反推技術 並給按鈕繫結推送方法 */
$(document).ready(function() {
dwr.engine.setActiveReverseAjax(true);
$('#send').click(function() {
DwrPush.push($('#msg').val());
});
});
// 回撥方法
function callback(msg) {
$('#ul').html($('#ul').html() + "</br>" + msg);
}
</script>
</html>DwrPush.java
package util;
import java.util.ArrayList;
import java.util.List;
import org.directwebremoting.Container;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ServerContextFactory;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.event.ScriptSessionEvent;
import org.directwebremoting.event.ScriptSessionListener;
import org.directwebremoting.extend.ScriptSessionManager;;
/***
* Dwr反向推送類
* @author liaot
* @time 2017/12/09
*/
public class DwrPush {
// 記錄所有線上的ScriptSession
private final static List<ScriptSession> SESSIONS = new ArrayList<ScriptSession>();
static {
// 得到DWR容器
Container container = ServerContextFactory.get().getContainer();
// 從DWR中得到會話管理器
ScriptSessionManager manager = container.getBean(ScriptSessionManager.class);
// 建立一個會話監聽器
ScriptSessionListener ssl = new ScriptSessionListener() {
@Override
public void sessionCreated(ScriptSessionEvent e) {
SESSIONS.add(e.getSession());
System.out.println("user login " + SESSIONS.size());
}
@Override
public void sessionDestroyed(ScriptSessionEvent e) {
SESSIONS.remove(e.getSession());
System.out.println("user exit " + SESSIONS.size());
}
};
// 給管理器新增監聽器
manager.addScriptSessionListener(ssl);
}
public void push(String msg) {
// 得到當前使用者的ScriptSession
ScriptSession seft = WebContextFactory.get().getScriptSession();
System.out.println(seft);
for (ScriptSession session : SESSIONS) {
// 建立指令碼 快取 執行指定function 傳遞msg引數
ScriptBuffer sb = new ScriptBuffer();
//呼叫 jsp頁面上 callback 方法
sb.appendCall("callback", seft.getCreationTime() + " : " + msg);
//將指令碼新增到回話中
session.addScript(sb);
}
}
}參考資料
- dwr 官網: http://directwebremoting.org/dwr/
- imooc: https://www.imooc.com/learn/784