ChannelInterceptor 攔截器攔截 ws 協議的請求/響應(`send/subscribe`)，不攔截 http 協議的請求/響應。 [TOC] # 1. ChannelInterceptor使用步驟 攔截器使用步驟如下： **1. 實現攔截器接口** ```java //方法調用順序：preSend -> postSend -> afterSendCompletion public class SocketChannelInterceptor implements ChannelInterceptor { /** * 消息發送到目標方法之前被調用 * * @param message * @param channel * @return */ @Override public Message<?> preSend(Message<?> message, MessageChannel channel) { System.out.println("preSend->"); return ChannelInterceptor.super.preSend(message, channel); } /** * 消息正在發送過程中被調用，主要用這個方法就行 * * @param message * @param channel * @param sent */ @Override public void postSend(Message<?> message, MessageChannel channel, boolean sent) { StompHeaderAccessor header = StompHeaderAccessor.wrap(message); System.out.println("postSend->" + header.getDestination()); } /** * 消息發送完成之后被調用，一般用來做資源釋放等工作。 * * @param message * @param channel * @param sent * @param ex */ @Override public void afterSendCompletion(Message<?> message, MessageChannel channel, boolean sent, Exception ex) { System.out.println("afterSendCompletion->"); ChannelInterceptor.super.afterSendCompletion(message, channel, sent, ex); } } ``` **2. 配置類中添加攔截器** ```java @Configuration @EnableWebSocketMessageBroker public class WebSocketConfig implements WebSocketMessageBrokerConfigurer { @Override public void configureClientInboundChannel(ChannelRegistration registration) { registration.interceptors(new SocketChannelInterceptor()); } @Override public void configureClientOutboundChannel(ChannelRegistration registration) { registration.interceptors(new SocketChannelInterceptor()); } } ``` <br/> # 2. 攔截器實現用戶上線下線通知功能 ```java public class SocketChannelInterceptor implements ChannelInterceptor { @Override public void postSend(Message<?> message, MessageChannel channel, boolean sent) { StompHeaderAccessor header = StompHeaderAccessor.wrap(message); if (header.getCommand() == null) return; if (header.getCommand().equals(StompCommand.CONNECT)) { System.out.println("用戶上線了"); } if ( header.getCommand().equals(StompCommand.DISCONNECT)) { System.out.println("用戶下線了"); } } } ```