SpringBoot中使用WebSocket的教程分享

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

@Component
public class WebSocketAPI extends TextWebSocketHandler {
    @Override //该方法会在websocket连接成功后被调用
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        //WebSocketSession是websocket连接对应的会话
        System.out.println("建立连接了");
    }
    @Override //该方法是在websocket收到消息的时候自动调用
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
        //message 为收到的消息
        System.out.println("发送消息："+message.toString());
        //session是个会话，里面记录了通信双方,通过session对象调用send方法实现服务器推送消息
        session.sendMessage(message);
        message.getPayload(); //获取的message字符串
    }
    @Override //该方法是在websocket连接出现异常的时候自动调用的
    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        //exception记录了异常信息
        System.out.println("连接出现异常了");
    }
    @Override //该方法是在websocket连接关闭后自动调用的
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        //status 为关闭的状态
        System.out.println("连接关闭了");
    }
}

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
    @Autowired
    private WebSocketAPI webSocketAPI;
    @Override //通过该方法，把创建好的Handler类注册到具体的路径上
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        //当浏览器，websocket的请求路径是/test的时候，就会调用到webSocketTest中的方法
        registry.addHandler(webSocketAPI,"/websocketMessage");
    }
}

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
    @Autowired
    private WebSocketAPI webSocketAPI;
    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(webSocketAPI,"/websocketMessage").
                // 通过注册特定的HttpSession拦截器，就可以把
                // 用户给HttpSession中添加的Attribute键值对，往WebSocketSession中也添加一份
                addInterceptors(new HttpSessionHandshakeInterceptor());
    }
}

    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        User user = (User)session.getAttributes().get("user");
        System.out.println("建立连接");
    }

@Component
public class WebSocketSessionManage {
    private ConcurrentHashMap<Integer, WebSocketSession> websocketSessions = new ConcurrentHashMap<>();
    //用户连接，添加连接关系
    public void addWebSocketSession(Integer userId,WebSocketSession webSocketSession){
        //用户已经上线，防止多开
        if(websocketSessions.containsKey(userId)){
            return;
        }
        websocketSessions.put(userId,webSocketSession);
    }
    //用户掉线，删除连接关系
    public void delWebSocketSession(Integer userId,WebSocketSession webSocketSession){
        WebSocketSession get = websocketSessions.get(userId);
        //只有关系中存在自己的连接信息，才删除
        if(get == webSocketSession){
            websocketSessions.remove(userId);
        }
    }
    //根据用户id获取WebSocketSession
    public WebSocketSession getWebSocketSession(Integer userId){
        return websocketSessions.get(userId);
    }
}

 //websocket传输消息
	 //创建websocket实例
	let websocket = new WebSocket("ws://" + location.host + "/websocketMessage");
	//绑定一些函数
	websocket.onopen = function(){
	    console.log('建立连接')
	}
	websocket.onmessage = function(e){
	    //e.data为收到服务端推送的消息
	    //e.data为一个json字符串，可以使用JSON.prase(e.data)转换为js对象
	    let resp = JSON.prase(e.data);
	    console.log('收到消息：'+resp)
	}
	websocket.onerror = function(){
	    console.log('出现异常')
	}
	websocket.onclose = function(){
	    console.log('关闭连接')
	}
	//使用websocket实例调用send方法即可向服务器发送消息
	//注意：参数为字符串，不能为js对象
	//要发送json格式的数据，将json对象序列化为字符串，JSON.stringfy(json)
	websocket.send("hehe");