一、WebSocket+Spring Boot實例

1 新建一個Spring Boot項目，選擇Web、支持Thymeleaf模板、WebSocket。

下一步，選擇依賴：Web、支持Thymeleaf模板、Websocket

完畢以後，項目目錄如下（支持支持Thymeleaf模板，會在resources文件價下自動新建static、templates文件夾。這裏放置html頁面）：

2 配置application.properties文件

server.port=9999
server.servlet.context-path=/demo

需要配置端口及路徑，才能正確使用路徑http://localhost:9999/demo/page。
否則默認是http://localhost:8080/page，因爲Spring Boot默認是8080端口。

3 pom.xml

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

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.60</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>

4 關鍵的類

4.1 啓動類DemoApplication

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

}

4.2 WebSocketConfig

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

4.3 WebSocketServer

@ServerEndpoint("/imserver/{userId}")
@Component
@Slf4j
public class WebSocketServer {
    /**靜態變量，用來記錄當前在線連接數。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，用來存放每個客戶端對應的MyWebSocket對象。*/
    private static ConcurrentHashMap<String,WebSocketServer> webSocketMap = new ConcurrentHashMap<>();
    /**與某個客戶端的連接會話，需要通過它來給客戶端發送數據*/
    private Session session;
    /**接收userId*/
    private String userId="";

    /**
     * 連接建立成功調用的方法*/
    @OnOpen
    public void onOpen(Session session, @PathParam("userId") String userId) {
        this.session = session;
        this.userId=userId;
        if(webSocketMap.containsKey(userId)){
            webSocketMap.remove(userId);
            webSocketMap.put(userId,this);
            //加入set中
        }else{
            webSocketMap.put(userId,this);
            //加入set中
            addOnlineCount();
            //在線數加1
        }

        log.info("用戶連接:"+userId+",當前在線人數爲:" + getOnlineCount());

        try {
            sendMessage("連接成功");
        } catch (IOException e) {
            log.error("用戶:"+userId+",網絡異常!!!!!!");
        }
    }

    /**
     * 連接關閉調用的方法
     */
    @OnClose
    public void onClose() {
        if(webSocketMap.containsKey(userId)){
            webSocketMap.remove(userId);
            //從set中刪除
            subOnlineCount();
        }
        log.info("用戶退出:"+userId+",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*/
    @OnMessage
    public void onMessage(String message, Session session) {
        log.info("用戶消息:"+userId+",報文:"+message);
        //可以羣發消息
        //消息保存到數據庫、redis
        if(!StringUtils.isEmpty(message)){
            try {
                //解析發送的報文
                JSONObject jsonObject = JSON.parseObject(message);
                //追加發送人(防止串改)
                jsonObject.put("fromUserId",this.userId);
                String toUserId=jsonObject.getString("toUserId");
                //傳送給對應toUserId用戶的websocket
                if(!StringUtils.isEmpty(toUserId)&&webSocketMap.containsKey(toUserId)){
                    webSocketMap.get(toUserId).sendMessage(jsonObject.toJSONString());
                }else{
                    log.error("請求的userId:"+toUserId+"不在該服務器上");
                    //否則不在這個服務器上，發送到mysql或者redis
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }

    /**
     *
     * @param session
     * @param error
     */
    @OnError
    public void onError(Session session, Throwable error) {
        log.error("用戶錯誤:"+this.userId+",原因:"+error.getMessage());
        error.printStackTrace();
    }
    /**
     * 實現服務器主動推送
     */
    public void sendMessage(String message) throws IOException {
        this.session.getBasicRemote().sendText(message);
    }


    /**
     * 發送自定義消息
     * */
    public static void sendInfo(String message,@PathParam("userId") String userId) throws IOException {
        log.info("發送消息到:"+userId+"，報文:"+message);
        if(!StringUtils.isEmpty(userId)&&webSocketMap.containsKey(userId)){
            webSocketMap.get(userId).sendMessage(message);
        }else{
            log.error("用戶"+userId+",不在線！");
        }
    }

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

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

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

4.4 DemoController

@RestController
public class DemoController {
    @GetMapping("index")
    public ResponseEntity<String> index(){
        return ResponseEntity.ok("success request");
    }

    @GetMapping("page")
    public ModelAndView page(){
        return new ModelAndView("websocket");
    }

    @RequestMapping("/push/{toUserId}")
    public ResponseEntity<String> pushToWeb(String message, @PathVariable String toUserId) throws IOException {
        WebSocketServer.sendInfo(message,toUserId);
        return ResponseEntity.ok("MSG SEND SUCCESS");
    }
}

4.5 websocket.html

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>websocket通訊</title>
</head>
<script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.js"></script>
<script>
    var socket;
    function openSocket() {
        if(typeof(WebSocket) == "undefined") {
            console.log("您的瀏覽器不支持WebSocket");
        }else{
            console.log("您的瀏覽器支持WebSocket");
            //實現化WebSocket對象，指定要連接的服務器地址與端口  建立連接
            //等同於socket = new WebSocket("ws://localhost:8888/xxxx/im/25");
            //var socketUrl="${request.contextPath}/im/"+$("#userId").val();
            var socketUrl="http://localhost:9999/demo/imserver/"+$("#userId").val();
            socketUrl=socketUrl.replace("https","ws").replace("http","ws");
            console.log(socketUrl);
            if(socket!=null){
                socket.close();
                socket=null;
            }
            socket = new WebSocket(socketUrl);
            //打開事件
            socket.onopen = function() {
                console.log("websocket已打開");
                //socket.send("這是來自客戶端的消息" + location.href + new Date());
            };
            //獲得消息事件
            socket.onmessage = function(msg) {
                console.log(msg.data);
                //發現消息進入    開始處理前端觸發邏輯
            };
            //關閉事件
            socket.onclose = function() {
                console.log("websocket已關閉");
            };
            //發生了錯誤事件
            socket.onerror = function() {
                console.log("websocket發生了錯誤");
            }
        }
    }
    function sendMessage() {
        if(typeof(WebSocket) == "undefined") {
            console.log("您的瀏覽器不支持WebSocket");
        }else {
            console.log("您的瀏覽器支持WebSocket");
            console.log('{"toUserId":"'+$("#toUserId").val()+'","contentText":"'+$("#contentText").val()+'"}');
            socket.send('{"toUserId":"'+$("#toUserId").val()+'","contentText":"'+$("#contentText").val()+'"}');
        }
    }
</script>
<body>
<p>【userId】：<div><input id="userId" name="userId" type="text" value="10"></div>
<p>【toUserId】：<div><input id="toUserId" name="toUserId" type="text" value="20"></div>
<p>【toUserId】：<div><input id="contentText" name="contentText" type="text" value="hello websocket"></div>
<p>【操作】：<div><a onclick="openSocket()">開啓socket</a></div>
<p>【操作】：<div><a onclick="sendMessage()">發送消息</a></div>
</body>

</html>

5 瀏覽器訪問

http://localhost:9999/demo/page