SpringCloud 后端使用webSocket向前端推送消息

末蓝、 2022-09-08 11:48 446阅读 0赞

# 1、webSocket #

webSocket长连接是一种在单个tcp连接上进行全双工通信的协议，允许双向数据推送。一般微服务提供的restful API只是对前端请求做出相应。使用webSocket可以实现后端主动向前端推送消息。

## 2、springboot使用webSocket ##

### 1、pom文件添加依赖 ###

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

### 2、添加webSocket配置 ###

@Configuration
    @EnableWebSocket
    public class WebSocketAutoConfig implements WebSocketConfigurer {
    
        @Override
        public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
            // webSocket通道
            // 指定处理器和路径
            registry.addHandler(new WebSocketHandler(), "/websocket")
                     // 指定自定义拦截器
                    .addInterceptors(new WebSocketInterceptor())
                    // 允许跨域
                    .setAllowedOrigins("*");
            // sockJs通道
            registry.addHandler(new WebSocketHandler(), "/sock-js")
                    .addInterceptors(new WebSocketInterceptor())
                    .setAllowedOrigins("*")
                    // 开启sockJs支持
                    .withSockJS();
        }
    }

处理器代码：

public class WebSocketHandler extends AbstractWebSocketHandler {
    
        /**
        *  存储sessionId和webSocketSession
        *  需要注意的是，webSocketSession没有提供无参构造，不能进行序列化，也就不能通过redis存储
        *  在分布式系统中，要想别的办法实现webSocketSession共享
        */
        private static Map<String, WebSocketSession> sessionMap = new ConcurrentHashMap<>();
        private static Map<String, String> userMap = new ConcurrentHashMap<>();
    
        /**
         * webSocket连接创建后调用
         */
        @Override
        public void afterConnectionEstablished(WebSocketSession session) {
             // 获取参数
            String user = String.valueOf(session.getAttributes().get("user"));
            userMap.put(user, session.getId());
            sessionMap.put(session.getId(), session);
        }
    
        /**
         * 接收到消息会调用
         */
        @Override
        public void handleMessage(WebSocketSession session, WebSocketMessage<?> message) throws Exception {
            if (message instanceof TextMessage) {
    
            } else if (message instanceof BinaryMessage) {
                
            } else if (message instanceof PongMessage) {
               
            } else {
                System.out.println("Unexpected WebSocket message type: " + message);
            }
        }
    
        /**
         * 连接出错会调用
         */
        @Override
        public void handleTransportError(WebSocketSession session, Throwable exception) {
            sessionMap.remove(session.getId());
        }
    
        /**
         * 连接关闭会调用
         */
        @Override
        public void afterConnectionClosed(WebSocketSession session, CloseStatus status) {
            sessionMap.remove(session.getId());
        }
    
        @Override
        public boolean supportsPartialMessages() {
            return false;
        }
    
        /**
        * 后端发送消息
        */
        public void sendMessage(String user, String message){
            String sessionId = userMap.get(user);
            WebSocketSession session = sessionMap.get(sessionId);
            session.sendMessage(new TextMessage(message));
        }
    }

自定义拦截器：

public class WebSocketInterceptor implements HandshakeInterceptor {
    
        /**
         * handler处理前调用,attributes属性最终在WebSocketSession里,可能通过webSocketSession.getAttributes().get(key值)获得
         */
        @Override
        public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Map<String, Object> attributes) {
            if (request instanceof ServletServerHttpRequest) {
                ServletServerHttpRequest serverHttpRequest = (ServletServerHttpRequest) request;
                // 获取请求路径携带的参数
                String user = serverHttpRequest.getServletRequest().getParameter("user");
                attributes.put("user", user);
                return true;
            } else {
                return false;
            }
        }
    
        @Override
        public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Exception exception) {
    
        }
    }

## 3、前端连接webSocket ##

WebSocket对象是H5新增的对象，低版本浏览器可能不支持，可以使用sockJs的方式连接

### WebSocket连接 ###

// 打开一个 web socket
    var ws = new WebSocket("ws://localhost:8080/websocket?user=Tony");
    ws.onopen = function() {
        // Web Socket 已连接上，使用 send() 方法发送数据
        ws.send("测试发送");
        console.log('open');
    };
    ws.onmessage = function (e) { 
        console.log('message', e.data);
    };
    ws.onclose = function() { 
        console.log('close');
    };

### SockJs连接 ###

## 4、SpringCloud使用zuul转发webSocket连接 ##

zuul网关还需要做额外的配置，添加自定义过滤器：

@Component
    public class WebSocketFilter extends ZuulFilter {
        @Override
        public String filterType() {
            return "pre";
        }
        @Override
        public int filterOrder() {
            return 0;
        }
        @Override
        public boolean shouldFilter() {
            return true;
        }
        @Override
        public Object run() {
            RequestContext context = RequestContext.getCurrentContext();
            HttpServletRequest request = context.getRequest();
            String upgradeHeader = request.getHeader("Upgrade");
            if (null == upgradeHeader) {
                upgradeHeader = request.getHeader("upgrade");
            }
            if (null != upgradeHeader && "websocket".equalsIgnoreCase(upgradeHeader)) {
                context.addZuulRequestHeader("connection", "Upgrade");
            }
            return null;
        }
    }

配置文件添加配置：

hystrix:
      command:
        default:
          execution:
            isolation:
              thread:
                timeoutInMilliseconds: 60000  #设置API网关中路由转发请求的HystrixCommand执行超时时间
    ribbon:
      ConnectTimeout: 3000 #设置路由转发请求的时候，创建请求连接的超时时间
      ReadTimeout: 60000  #用来设置路由转发请求的超时时间

## 5、网关使用SpringCloud Gateway无需做任何处理 ##

## 6、若使用了Nginx，需要添加配置 ##

配置示例：

map $http_upgrade $connection_upgrade {
            default upgrade;
            '' close;
        }
    
        upstream websocket {
            server 127.0.0.1:8080;
        }
    
        server {
            listen 80;
            location / {
                proxy_pass http://websocket;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection $connection_upgrade;
            }
        }

## 7. SpringCloud前端连接示例： ##

### SockJs连接 ###

### WebSocket连接 ###

// 打开一个 web socket
    var ws = new WebSocket("ws://(网关路径)/(服务名称)/websocket?user=Tony");
    ws.onopen = function() {
        // Web Socket 已连接上，使用 send() 方法发送数据
        ws.send("测试发送");
        console.log('open');
    };
    ws.onmessage = function (e) { 
        console.log('message', e.data);
    };
    ws.onclose = function() { 
        console.log('close');
    };