1. 项目介绍

• 客户端页面index.html可以输入消息，点击发送，通过ws协议发送到服务器端；
• 服务器端收到客户端消息后，广播给各个客户端；
• 服务器端页面server.html，可以输入消息，点击发送，通过ws双工通信推送给客户端；
• 客户端有显示服务器端广播消息的区域。

2. 项目目录结构

3. 项目代码分析

3.1 pom.xml文件添加必要依赖

   <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <!--WebSocket-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-websocket</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

        <dependency>
            <groupId>org.webjars</groupId>
            <artifactId>bootstrap</artifactId>
            <version>3.3.7-1</version>
        </dependency>
    </dependencies>

3.2 .java代码

• 新建WebSocket 的配置类WebSocketConfig.java

package com.springboot.websocket.websocket.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;

/**
 * WebSocket配置类
 *
 */
@Configuration
public class WebSocketConfig {

    @Bean
    public ServerEndpointExporter serverEndpointExporter() {
        return new ServerEndpointExporter();
    }
}

• WebSocket的服务端

package com.springboot.websocket.websocket.config;

import org.springframework.stereotype.Component;

import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.concurrent.CopyOnWriteArraySet;

/**
 * WebSocket的服务端
 * 因为WebSocket是类似客户端服务端的形式(采用ws协议)，
 * 那么这里的WebSocketServer其实就相当于一个ws协议的Controller
 * 直接@ServerEndpoint(“/websocket”)@Component启用即可，
 * 然后在里面实现@OnOpen,@onClose,@onMessage等方法
 */
@ServerEndpoint("/websocket")
@Component
public class WebSocketServer {

    //静态变量，用来记录当前在线连接数。应该把它设计成线程安全的。可选的
    private static int onlineCount = 0;
    //concurrent包的线程安全Set，用来存放每个客户端对应的MyWebSocket对象。必须要有的
    private static CopyOnWriteArraySet<WebSocketServer>
            webSocketSet = new CopyOnWriteArraySet<WebSocketServer>();

    //与某个客户端的连接会话，需要通过它来给客户端发送数据，必须
    private Session session;

    /**
     * 连接建立成功调用的方法
     */
    @OnOpen
    public void onOpen(Session session) {
        this.session = session;
        webSocketSet.add(this);     //加入set中
        addOnlineCount();           //在线数加1
        //一旦连接成功后就在控制台打印信息
        System.out.println("有新窗口开始监听,当前在线人数为" + getOnlineCount());
        try {
            //往客户端发送消息
            sendMessage("连接成功");
        } catch (IOException e) {
            System.out.println("WebSocket IO异常");
        }
    }

    /**
     * 连接关闭调用的方法
     */
    @OnClose
    public void onClose() {
        webSocketSet.remove(this);  //从set中删除
        subOnlineCount();           //在线数减1
        System.out.println("有连接关闭！当前在线人数为" + getOnlineCount());
    }

    /**
     * 收到客户端消息后调用的方法
     *
     * @param message 客户端发送过来的消息
     */
    @OnMessage
    public void onMessage(String message, Session session) {
        //message 是从客户端发送过来的消息，并在控制台打印
        System.out.println("收到客户端的信息:" + message);
        //群发消息
        for (WebSocketServer item : webSocketSet) {
            try {
                item.sendMessage(message);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * @param session
     * @param error
     */
    @OnError
    public void onError(Session session, Throwable error) {
        System.out.println("发生错误");
        error.printStackTrace();
    }

    /**
     * 实现服务器主动推送
     */
    public void sendMessage(String message) throws IOException {
        this.session.getBasicRemote().sendText(message);
    }


    /**
     * 群发自定义消息
     */
    public static void sendInfo(String message) throws IOException {
        System.out.println("推送消息内容:" + message);
        for (WebSocketServer item : webSocketSet) {
            try {
                item.sendMessage(message);
            } catch (IOException e) {
                continue;
            }
        }
    }

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

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

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

• WebSocketController.java 控制层代码

package com.springboot.websocket.websocket.controller;

import com.springboot.websocket.websocket.config.WebSocketServer;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

import java.io.IOException;

/**

 * WebSocketController
 */
@Controller
@RequestMapping("/socket")
public class WebSocketController {


    /**
     * 输入消息的页面
     * @return
     */
    @GetMapping("/send")
    public String sendMsg(){
        return "server";
    }

    /**
     * 推送数据接口
     * @Param message
     * @return
     */
    @RequestMapping("/push")
    public String pushMsg(@RequestParam("message")String message) {
        try {
            WebSocketServer.sendInfo(message);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "server";
    }
}

3.3 html页面代码

• 主页面index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>WebSocket</title>
</head>
<body>
<h1>WebScoket练习</h1>
<label>
    <input id="msg" type="text" name="message" style="width:215px;" />
    <input type="submit" id="btn" />
</label>
<br>


<div>
<ul id="message_show_ul">
</ul>
</div>
<script language="JavaScript">
    var send_message = document.getElementById("msg");
    var sub_button = document.getElementById("btn");
    var show_ul = document.getElementById("message_show_ul");
    var socket;
    if (typeof(WebSocket) == "undefined") {
        console.log("您的浏览器不支持WebSocket");
    } else {
        console.log("您的浏览器支持WebSocket");
        //实现化WebSocket对象，指定要连接的服务器地址与端口建立连接
        socket = new WebSocket("ws://localhost:8088/websocket");

        //打开事件
        socket.onopen = function () {
            console.log("Socket已打开");
            sub_button.onclick = function () {
                console.log(send_message);
                //下面这句话是往服务器发送消息
                socket.send("这是来自客户端的消息:" + send_message.value);
            };

        };

        //获得消息事件，从服务器获得消息
        socket.onmessage = function (msg) {

            var li_eme = document.createElement("li");
            li_eme.innerHTML = msg.data;
            show_ul.appendChild(li_eme);
            //控制台打印消息
            console.log(msg.data);
            //弹出框弹出消息
           // alert(msg.data);
        };

        //关闭事件
        socket.onclose = function () {
            console.log("Socket已关闭");
        };

        //发生了错误事件
        socket.onerror = function () {
            alert("Socket发生了错误");
        }
    }
</script>
</body>
</html>

• 服务器端页面server.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>WebSocketServer</title>
</head>
<body>
<h1>服务器端</h1>
<form id="login" action="/socket/push" method="get">
    <label>
        <input id="msg" type="text" name="message" style="width:215px;" />
        <input type="submit" id="btn"/>
    </label>
    <br>
</form>
</body>
</html>