SpringBoot + WebSocket 开发笔记

1. 服务端的实现，我尝试了两种方式：

• 第一种是用“@ServerEndPoint”注解来实现，实现简单；
• 第二种稍显麻烦，但是可以添加拦截器在WebSocket连接建立和断开前进行一些额外操作。

　　不管用哪种实现方式，都需要先导入jar包（如下），其中version根据实际springboot版本选择，避免冲突

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-websocket</artifactId>
    <!-- <version>1.3.5.RELEASE</version> -->
</dependency>

1.1 第一种实现方法

（1）WebSocket 业务逻辑实现。参数传递采用路径参数的方法，通过以下方式获取参数：

• @ServerEndpoint("/testWebSocket/{id}/{name}")
  

• public void onOpen(Session session, @PathParam("id") long id, @PathParam("name") String name)

import java.util.concurrent.CopyOnWriteArraySet;

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

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.RestController;

@ServerEndpoint("/testWebSocket/{id}/{name}")
@RestController
public class TestWebSocket {

    // 用来记录当前连接数的变量
    private static volatile 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
    private static CopyOnWriteArraySet<TestWebSocket> webSocketSet = new CopyOnWriteArraySet<TestWebSocket>();

    // 与某个客户端的连接会话，需要通过它来与客户端进行数据收发
    private Session session;
    
    private static final Logger LOGGER = LoggerFactory.getLogger(TestWebSocket.class);
    
　　@OnOpen
    public void onOpen(Session session, @PathParam("id") long id, @PathParam("name") String name) throws Exception {
        this.session = session;
        System.out.println(this.session.getId());
        webSocketSet.add(this);
        LOGGER.info("Open a websocket. id={}, name={}", id, name);
    }
    
    @OnClose
    public void onClose() {
        webSocketSet.remove(this);
        LOGGER.info("Close a websocket. ");
    }
    
    @OnMessage
    public void onMessage(String message, Session session) {
        LOGGER.info("Receive a message from client: " + message);
    }
    
    @OnError
    public void onError(Session session, Throwable error) {
        LOGGER.error("Error while websocket. ", error);
    }
    
    public void sendMessage(String message) throws Exception {
        if (this.session.isOpen()) {
            this.session.getBasicRemote().sendText("Send a message from server. ");
        }
    }
    
    public static synchronized int getOnlineCount() {
        return onlineCount;
    }

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

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

（2）配置ServerEndpointExporter，配置后会自动注册所有“@ServerEndpoint”注解声明的Websocket Endpoint

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

@Configuration
public class WebSocketConfig {

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

1.2 第二种实现方法

（1）WebSocket 业务逻辑实现。参数传递采用类似GET请求的方式传递，服务端的参数在拦截器中获取之后通过attributes传递给WebSocketHandler。

import java.util.ArrayList;
import java.util.concurrent.atomic.AtomicInteger;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.socket.CloseStatus;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.WebSocketMessage;
import org.springframework.web.socket.WebSocketSession;

@RestController
public class TestWebSocketController implements WebSocketHandler {
    
    private static AtomicInteger onlineCount = new AtomicInteger(0);
    
    private static final ArrayList<WebSocketSession> sessions = new ArrayList<>();
    
    private final Logger LOGGER = LoggerFactory.getLogger(TestWebSocketController.class);
    
    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        sessions.add(session);
        int onlineNum = addOnlineCount();
        LOGGER.info("Oprn a WebSocket. Current connection number: " + onlineNum);
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        sessions.remove(session);
        int onlineNum = subOnlineCount();
        LOGGER.info("Close a webSocket. Current connection number: " + onlineNum);
    }

    @Override
    public void handleMessage(WebSocketSession wsSession, WebSocketMessage<?> message) throws Exception {
        LOGGER.info("Receive a message from client: " + message.toString());
    }

    @Override
    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        LOGGER.error("Exception occurs on webSocket connection. disconnecting....");
        if (session.isOpen()) {
            session.close();
        }
        sessions.remove(session);
        subOnlineCount();
    }

    /*
     * 是否支持消息拆分发送：如果接收的数据量比较大，最好打开(true), 否则可能会导致接收失败。
     * 如果出现WebSocket连接接收一次数据后就自动断开，应检查是否是这里的问题。
     */
    @Override
    public boolean supportsPartialMessages() {
        return true;
    }

    
    public static int getOnlineCount() {
        return onlineCount.get();
    }
    
    public static int addOnlineCount() {
        return onlineCount.incrementAndGet();
    }
    
    public static int subOnlineCount() {
        return onlineCount.decrementAndGet();
    }

}

（2）HandShake 拦截器实现

import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.http.server.ServletServerHttpRequest;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.server.support.HttpSessionHandshakeInterceptor;

public class TestHandShakeInterceptor extends HttpSessionHandshakeInterceptor {
    
    private final Logger LOGGER = LoggerFactory.getLogger(TestHandShakeInterceptor.class);
    
    /*
     * 在WebSocket连接建立之前的操作，以鉴权为例
     */
    @Override
    public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, 
            WebSocketHandler wsHandler, Map<String, Object> attributes) throws Exception {
        
        LOGGER.info("Handle before webSocket connected. ");
        
        // 获取url传递的参数，通过attributes在Interceptor处理结束后传递给WebSocketHandler
        // WebSocketHandler可以通过WebSocketSession的getAttributes()方法获取参数
        ServletServerHttpRequest serverRequest = (ServletServerHttpRequest) request;
        String id = serverRequest.getServletRequest().getParameter("id");
        String name = serverRequest.getServletRequest().getParameter("name");

        if (tokenValidation.validateSign()) {
            LOGGER.info("Validation passed. WebSocket connecting.... ");
            attributes.put("id", id);
            attributes.put("name", name);
            return super.beforeHandshake(request, response, wsHandler, attributes);
        } else {
            LOGGER.error("Validation failed. WebSocket will not connect. ");
            return false;
        }
    }
    
    @Override
    public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response,
            WebSocketHandler wsHandler, Exception ex) {
        // 省略
    }

}

（3）WebSocket 配置类实现（注册WebSocket实现类，绑定接口，同时将实现类和拦截器绑定）

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;

import TestWebSocketController;
import TestHandShakeInterceptor;

@Configuration
@EnableWebMvc
@EnableWebSocket
public class WebSocketConfig extends WebMvcConfigurerAdapter implements WebSocketConfigurer {

    @Autowired
    private TestWebSocketController testWebSocketController;

    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(TestWebSocketController, "/testWebSocket")
                .addInterceptors(new TestHandShakeInterceptor()).setAllowedOrigins("*");
    }

}

1.3 补充说明

（1）在WebSocket实现过程中，尤其是通过“@ServerEndpoint”实现的时候，可能会出现注入失败的问题，即注入的Bean为null的问题。可以通过手动注入的方式来解决，需要改造实现类和SpringBoot启动类，如下：

@ServerEndpoint("testWebsocket")
@RestController
public class WebSocketController {

    private TestService testService;
    
    private static ApplicationContext applicationContext;
    
    @OnOpen
    public void onOpen(Session session) {
        testService = applicationContext.getBean(TestService.class);
    }

    @OnClose
    public void onClose() {}

    @OnMessage
    public void onMessage(String message, Session session) {}

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

    public static void setApplicationContext(ApplicationContext applicationContext) {
        WebSocketController.applicationContext = applicationContext;
    }
    
}

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

import WebSocketController;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
//        SpringApplication.run(Application.class, args);
        SpringApplication springApplication = new SpringApplication(Application.class);
        ConfigurableApplicationContext configurableApplicationContext = springApplication.run(args);
        WebSocketController.setApplicationContext(configurableApplicationContext);  // 解决WebSocket不能注入的问题
    }

}

2. 客户端的实现，我尝试了html和java WebSocketClient两种方式

2.1 html实现

<!DOCTYPE html>
<html>
<head>
    <title>WebSocket示例</title>
    <meta content='width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no' name='viewport' />
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>
    <input id="text" type="text"/>
    <button onclick="send()">发送消息</button>
    <hr/>
    <button onclick="closeWebSocket()">关闭WebSocket连接</button>
    <hr/>
    <div id="message"></div>
</body>

<script type="text/javascript">
    var websocket = null;
    //判断当前浏览器是否支持WebSocket
    if ('WebSocket' in window) {
        // 不带参数的写法
        websocket = new WebSocket("ws://127.0.0.1:18080/testWebsocket");
        // 通过路径传递参数的方法（服务端采用第一种方法"@ServerEndpoint"实现）
        websocket = new WebSocket("ws://127.0.0.1:18080/testWebsocket/23/Lebron");
        // 通过类似GET请求方式传递参数的方法（服务端采用第二种方法"WebSocketHandler"实现）
        websocket = new WebSocket("ws://127.0.0.1:18080/testWebsocket?id=23&name=Lebron");
    }
    else {
        alert('当前浏览器 Not support websocket')
    }

    //连接发生错误的回调方法
    websocket.onerror = function () {
        setMessageInnerHTML("WebSocket连接发生错误");
    };

    //连接成功建立的回调方法
    websocket.onopen = function () {
        setMessageInnerHTML("WebSocket连接成功");
    }

    //接收到消息的回调方法
    websocket.onmessage = function (event) {
        setMessageInnerHTML(event.data);
    }

    //连接关闭的回调方法
    websocket.onclose = function () {
        setMessageInnerHTML("WebSocket连接关闭");
    }

    //监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。
    window.onbeforeunload = function () {
        closeWebSocket();
    }

    //将消息显示在网页上
    function setMessageInnerHTML(innerHTML) {
        document.getElementById('message').innerHTML += innerHTML + '<br/>';
    }

    //关闭WebSocket连接
    function closeWebSocket() {
        websocket.close();
    }

    //发送消息
    function send() {
        var message = document.getElementById('text').value;
        websocket.send(message);
    }
</script>
</html>

2.2 Java WebSocketClient实现

（1）WebSocketClient 实现类

import java.net.URI;

import org.java_websocket.client.WebSocketClient;
import org.java_websocket.drafts.Draft;
import org.java_websocket.handshake.ServerHandshake;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class TestWebSocketClient extends WebSocketClient {
    
    private final Logger LOGGER = LoggerFactory.getLogger(TestWebSocketClient.class);
    
    public TestWebSocketClient(URI serverUri) {
        super(serverUri);
    }
    
    public TestWebSocketClient(URI serverUri, Draft protocolDraft) {
        super(serverUri, protocolDraft);
    }

    @Override
    public void onOpen(ServerHandshake serverHandshake) {
        LOGGER.info("Open a WebSocket connection on client. ");
    }
    
    @Override
    public void onClose(int arg0, String arg1, boolean arg2) {
        LOGGER.info("Close a WebSocket connection on client. ");
    }

    @Override
    public void onMessage(String msg) {
        LOGGER.info("WebSocketClient receives a message: " + msg);
    }

    @Override
    public void onError(Exception exception) {
        LOGGER.error("WebSocketClient exception. ", exception);
    }

}

（2）WebSocketClient 发送数据

String serverUrl = "ws://127.0.0.1:18080/testWebsocket"
URI recognizeUri = new URI(serverUrl);
client = new TestWebSocketClient(recognizeUri, new Draft_6455());
client.connect();
client.send("This is a message from client. ");