Springboot使用WebSocket发送消息

1. 创建springboot项目，引入spring-boot-starter-websocket依赖

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

完整项目依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.5.9</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.mutest</groupId><artifactId>websocket-demo</artifactId><version>0.0.1-SNAPSHOT</version><name>websocket-demo</name><description>websocket demo</description><properties><java.version>8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-websocket</artifactId></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency></dependencies><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

2. 对websocket进行配置config
registerWebSocketHandlers()方法参数是WebSocketHandlerRegistry 。调用WebSocketHandlerRegistry 的addHandler方法传递处理器和路径。处理器参数是上一步创建的TextWebSocketHandler 的子类。路径是客户端调用时跟在端口后的路径。再调用WebSocketHandlerRegistry 的setAllowedOrigins方法传递星号，允许跨域访问。

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {@Autowiredprivate MyWsHandler myWsHandler;@Overridepublic void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {registry.addHandler(myWsHandler, "myWs")//允许跨域.setAllowedOrigins("*");}
}

WebSocketHandlerRegistry
addHandler()方法第一个传输传递处理器，第一个参数传递路径
setAllowedOrigins()方法设置允许源，传递星号，否则跨域。

3.定义处理器MyWsHandler

@Component
@Slf4j
public class MyWsHandler extends AbstractWebSocketHandler {@Overridepublic void afterConnectionEstablished(WebSocketSession session) {log.info("建立ws连接");WsSessionManager.add(session.getId(), session);}@Overrideprotected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {// 接收客户端/浏览器端的消息 message.getPayload()消息体String payload = message.getPayload();log.info("server 接收到客户端/浏览器端的消息 " + payload);log.info("发送文本消息");//服务端准备给客户端/浏览器端发送消息session.sendMessage(new TextMessage("server 发送给的消息 " + payload + "，发送时间:" + LocalDateTime.now().toString()));}@Overrideprotected void handleBinaryMessage(WebSocketSession session, BinaryMessage message) throws Exception {log.info("发送二进制消息");}@Overridepublic void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {log.error("异常处理");WsSessionManager.removeAndClose(session.getId());}@Overridepublic void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {log.info("关闭ws连接");WsSessionManager.removeAndClose(session.getId());}
}

4. 单播/多播发送消息
在MyWsHandler中，handleTextMessage方法使用的是单播发送消息，如果要给客户端/浏览器端发送广播消息该如何发送呢，只需遍历所有客户端/浏览器端的Session即可，通过Session广播消息。

@Service
@Slf4j
public class WsService {/*** 发送消息** @param session 连接信息* @param text    消息*/public void sendMsg(WebSocketSession session, String text) throws IOException {session.sendMessage(new TextMessage(text));}/*** 广播消息** @param text 消息*/public void broadcastMsg(String text) throws IOException {for (WebSocketSession session : WsSessionManager.SESSION_POOL.values()) {session.sendMessage(new TextMessage(text));}}
}

5. 设置定时任务发送广播消息

@Slf4j
@Component
public class MessageJob {@AutowiredWsService wsService;/*** 每5s发送*/@Scheduled(cron = "0/5 * * * * *")public void run() {try {log.info("推送消息===>" + LocalDateTime.now().toString());wsService.broadcastMsg("自动生成消息 " + LocalDateTime.now().toString());} catch (IOException e) {e.printStackTrace();}}
}

6. 管理客户端/浏览器端的Session工具类

@Slf4j
public class WsSessionManager {/*** 保存连接 session 的地方*/public static ConcurrentHashMap<String, WebSocketSession> SESSION_POOL = new ConcurrentHashMap<>();/*** 添加 session** @param key key*/public static void add(String key, WebSocketSession session) {// 添加 sessionSESSION_POOL.put(key, session);}/*** 删除 session,会返回删除的 session** @param key key* @return WebSocketSession*/public static WebSocketSession remove(String key) {// 删除 sessionreturn SESSION_POOL.remove(key);}/*** 删除并同步关闭连接** @param key key*/public static void removeAndClose(String key) {WebSocketSession session = remove(key);if (session != null) {try {// 关闭连接session.close();} catch (IOException e) {// todo: 关闭出现异常处理e.printStackTrace();}}}/*** 获得 session** @param key key* @return WebSocketSession*/public static WebSocketSession get(String key) {// 获得 sessionreturn SESSION_POOL.get(key);}
}