Websocket實現Java后台主動推送消息到前台

寫在前面

需求: 項目測試, 缺少用戶登錄失敗給admin推送消息, 想到這個方式, 當用戶登錄失敗時, admin用戶會在頁面看到咣咣亂彈的alert. 

正文

pom.xml

        <!-- webSocket 開始-->
        <dependency>
            <groupId>javax.websocket</groupId>
            <artifactId>javax.websocket-api</artifactId>
            <version>1.1</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>
        <!-- webSocket 結束-->

Websocket.java

package com.jeecg.webSocket;

import net.sf.json.JSONObject;

import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

@ServerEndpoint("/webSocket/{username}")
public class WebSocket {
    private static int onlineCount = 0;
    private static Map<String, WebSocket> clients = new ConcurrentHashMap<String, WebSocket>();
    private Session session;
    private String username;

    @OnOpen
    public void onOpen(@PathParam("username") String username, Session session) throws IOException {

        this.username = username;
        this.session = session;

        addOnlineCount();
        clients.put(username, this);
        System.out.println("已連接");
    }

    @OnClose
    public void onClose() throws IOException {
        clients.remove(username);
        subOnlineCount();
    }

    @OnMessage
    public void onMessage(String message) throws IOException {

        JSONObject jsonTo = JSONObject.fromObject(message);
        String mes = (String) jsonTo.get("message");

        if (!jsonTo.get("To").equals("All")){
            sendMessageTo(mes, jsonTo.get("To").toString());
        }else{
            sendMessageAll("給所有人");
        }
    }

    @OnError
    public void onError(Session session, Throwable error) {
        error.printStackTrace();
    }

    public void sendMessageTo(String message, String To) throws IOException {
        for (WebSocket item : clients.values()) {
            if (item.username.equals(To) )
                item.session.getAsyncRemote().sendText(message);
        }
    }

    public void sendMessageAll(String message) throws IOException {
        for (WebSocket item : clients.values()) {
            item.session.getAsyncRemote().sendText(message);
        }
    }

    public static synchronized int getOnlineCount() {
        return onlineCount;
    }

    public static synchronized void addOnlineCount() {
        WebSocket.onlineCount++;
    }

    public static synchronized void subOnlineCount() {
        WebSocket.onlineCount--;
    }

    public static synchronized Map<String, WebSocket> getClients() {
        return clients;
    }
}

fineui_home.jsp

<script>
    var websocket = null;
    var host = document.location.host;

    // 獲得當前登錄人員的userName
    var username = '${loginUserName}';

    // 獲取項目名
    var webName = '${webName}';

    //判斷當前瀏覽器是否支持WebSocket
    if ('WebSocket' in window) {
        // 瀏覽器支持Websocket
        websocket = new WebSocket('ws://' + host + '/' + webName + '/webSocket/' + username);
    } else {
        // 瀏覽器 Not support websocket
    }

    //WebSocket連接發生錯誤的回調方法
    websocket.onerror = function () {
        setMessageInnerHTML("WebSocket連接發生錯誤");
    };

    //WebSocket連接成功建立的回調方法
    websocket.onopen = function () {
        setMessageInnerHTML("WebSocket連接成功");
    };

    //接收到消息的回調方法
    websocket.onmessage = function (event) {
        alertTip(event.data);
        // websocket.close();
        // alert("webSocket已關閉！")
    };

    //監聽窗口關閉事件，當窗口關閉時，主動去關閉websocket連接，防止連接還沒斷開就關閉窗口，server端會拋異常。
    window.onbeforeunload = function () {
        closeWebSocket();
    };

    //關閉WebSocket連接
    function closeWebSocket() {
        websocket.close();
    }

    //連接關閉的回調方法
    websocket.onclose = function () {
        setMessageInnerHTML("WebSocket連接關閉");
    };

    //將消息顯示在網頁上
    function setMessageInnerHTML(innerHTML) {
        // document.getElementById('message').innerHTML += innerHTML + '<br/>';
    }
</script>

業務調用

WebSocket ws = new WebSocket();
JSONObject jo = new JSONObject();
jo.put("message", "這個比密碼不對還想登錄!");
jo.put("To", "admin");// 給用戶名為admin的用戶推送
try {
    ws.onMessage(jo.toString());
} catch (IOException e) {
    e.printStackTrace();
}

感謝

• https://www.cnblogs.com/best/p/5695570.html

• https://www.cnblogs.com/freud/p/8397934.html