WebSocket教程(二)

時間 2019-12-14

標籤 websocket 教程简体版

原文原文鏈接

運行環境：jdk8 tomcat8   無須其餘jar包。

package com.reach.socketController;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CopyOnWriteArraySet;

import javax.annotation.Resource;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint(value ="/newwebsocket/{userId}")
public class Webcomment {
    @Resource
    private Webcomment webcomment;
    
    //靜態變量，用來記錄當前在線鏈接數。應該把它設計成線程安全的。
    private static int onlineCount = 0;
    //concurrent包的線程安全Set，用來存放每一個客戶端對應的MyWebSocket對象。若要實現服務端與單一客戶端通訊的話，能夠使用Map來存放，其中Key能夠爲用戶標識
    private static CopyOnWriteArraySet<Webcomment> webSocketSet = new CopyOnWriteArraySet<Webcomment>();  
　　//線程安全的Map  
    private static ConcurrentHashMap<String,Session> webSocketMap = new ConcurrentHashMap<String,Session>();//創建鏈接的方法
    @OnOpen
    public void onOpen(Session session,@PathParam("userId")String  userId){
        /*獲取從/websocket開始的整條連接，用於獲取userId？***=***的參數
        String uri = session.getRequestURI().toString();*/
    webSocketMap.put(userId, session);
    addOnlineCount(); //在線數加
    System.out.println(userId+"進入聊天室");
    System.out.println("有新鏈接加入！當前在線人數爲" + getOnlineCount());
    }
    
    /**
    * 鏈接關閉調用的方法
    */
    @OnClose
    public void onClose(Session session){
    Map<String, String> map = session.getPathParameters();
    webSocketMap.remove(map.get("userId")); //從set中刪除
    for(String user:webSocketMap.keySet()){
    System.out.println(user);
    }
    subOnlineCount(); //在線數減
    System.out.println("有一鏈接關閉！當前在線人數爲" + getOnlineCount());
    }
    
    /**
    * 收到客戶端消息後調用的方法
    * @param message 客戶端發送過來的消息
    * @param session 可選的參數
    */
    @OnMessage
    public void onMessage(String message, Session session) {
    System.out.println("來自客戶端的消息:" + message);
    //獲取用戶ID
    Map<String, String> map = session.getPathParameters();
    String userId = map.get("userId");
    for(String user:webSocketMap.keySet()){
        try {
            sendMessage(user+"你好，我是"+userId+"   "+message,webSocketMap.get(user));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    }
    
    /**
    * 發生錯誤時調用
    * @param session
    * @param error
    */
    @OnError
    public void onError(Session session, Throwable error){
    System.out.println("發生錯誤");
    error.printStackTrace();
    }
    
    public void sendMessage(String message,Session session) throws IOException{
        if(session.isOpen()){
        session.getAsyncRemote().sendText(message);
        }
        //this.session.getAsyncRemote().sendText(message);
        }
    
    
    
    public static synchronized int getOnlineCount() {
        return onlineCount;
        }
    public static synchronized void addOnlineCount() {
        Webcomment.onlineCount++;
        }
    public static synchronized void subOnlineCount() {
        Webcomment.onlineCount--;
        }
}

html代碼，能夠單獨創建html，無須放在項目中javascript

<!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>
  <title> new document </title>
  <meta name="generator" content="editplus" />
  <meta name="author" content="" />
  <meta name="keywords" content="" />
  <meta name="description" content="" />
  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  <script src="jquery-1.8.3.min.js" type="text/javascript"></script>
 </head>

 <body>


  <center>
Welcome<br/><input id="text" type="text"/>
<button onclick="send()">發送消息</button>
<hr/>
<button onclick="closeWebSocket()">關閉WebSocket鏈接</button>
<hr/>
<div id="message"></div>




 </body>
 <script type="text/javascript">
var websocket = null;
//判斷當前瀏覽器是否支持WebSocket
if ('WebSocket' in window) {
alert('當前瀏覽器支持 websocket');
websocket = new WebSocket("ws://localhost:8080/Y-websocket/newwebsocket/234");
}
else {
alert('當前瀏覽器 Not support websocket')
}
//鏈接發生錯誤的回調方法
websocket.onerror = function () {
setMessageInnerHTML("WebSocket鏈接發生錯誤");
};
//鏈接成功創建的回調方法
websocket.onopen = function () {
setMessageInnerHTML("WebSocket鏈接成功");
}
//接收到消息的回調方法
websocket.onmessage = function (event) {
setMessageInnerHTML(event.data);
}
//鏈接關閉的回調方法
websocket.onclose = function () {
setMessageInnerHTML("WebSocket鏈接關閉");
}
//監聽窗口關閉事件，當窗口關閉時，主動去關閉websocket鏈接，防止鏈接還沒斷開就關閉窗口，server端會拋異常。
window.onbeforeunload = function () {
closeWebSocket();
}
//將消息顯示在網頁上
function setMessageInnerHTML(innerHTML) {
document.getElementById('message').innerHTML += innerHTML + '<br/>';
}
//關閉WebSocket鏈接
function closeWebSocket() {
websocket.close();
}
//發送消息
function send() {
var message = document.getElementById('text').value;
websocket.send(message);
}
</script>
</html>