javax.websocket.DeploymentException: The HTTP response from the server [404] did not permit the HTTP

解决办法：少两个文件：

WebSocketConfig.java  

@Configuration
public class WebSocketConfig {/*** 注入一个ServerEndpointExporter,该Bean会自动注册使用@ServerEndpoint注解申明的websocket endpoint*/@Beanpublic ServerEndpointExporter serverEndpointExporter() {return new ServerEndpointExporter();}}

和 

WebSocketManager.java 

@Component
public class WebSocketManager {private static final Map<String, List<Session>> sessionsMap = new ConcurrentHashMap<>();public static void addSession(String sid, Session session) {sessionsMap.computeIfAbsent(sid, k -> new CopyOnWriteArrayList<>()).add(session);}public static void removeSession(String sid, Session session) {List<Session> sessionList = sessionsMap.get(sid);if (sessionList != null) {sessionList.remove(session);if (sessionList.isEmpty()) {sessionsMap.remove(sid);}}}public static List<Session> getSessions(String sid) {return sessionsMap.getOrDefault(sid, Collections.emptyList());}public static void sendToAll(String sid, String message) throws IOException {for (Session session : getSessions(sid)) {session.getBasicRemote().sendText(message);}}
}

加上这两个文件，就可以了