spring-websocket - 添加 STOMP header 而不在 ChannelInterceptorAdapter 上重新创建消息

Question

我需要向 STOMP 消息添加 header ，目前它的工作方式如下，但我正在重新创建消息，是否可以只添加 native header 而无需重新创建消息以提高性能。

public class MyChannelInterceptor extends ChannelInterceptorAdapter {


    @Override
      public Message<?> preSend(Message<?> message, MessageChannel channel) {
        StompHeaderAccessor accessor = StompHeaderAccessor.wrap(message);

        StompCommand command = accessor.getCommand();
        if(command != null) {
            log.debug("Receiving msg {} from {}",command,accessor.getUser().getName());
            if(command == StompCommand.SEND) {
                log.debug("Adding expires header to  msg {} from {}",command,accessor.getUser().getName());
                String ttlString = accessor.getFirstNativeHeader("ttl");
                long ttl = 30000;
                try {
                    ttl = Long.parseLong(ttlString);
                } 
                catch(Exception ex) {
                    log.error("TTL header received but not in correct format {}",ttlString);
                }
                accessor.addNativeHeader("expires", Long.toString(System.currentTimeMillis() + ttl));

                return MessageBuilder.createMessage(message.getPayload(), accessor.getMessageHeaders());
            }
        }
        return message;
      }

}

Answer 1

这就是我要找的

StompHeaderAccessor accessor = MessageHeaderAccessor.getAccessor(message, StompHeaderAccessor.class);

上面的代码将获取消息的实际 StompHeaderAccessor，因此如果您操作 native header ，它们会直接反射(reflect)在消息上

StompHeaderAccessor accessor = StompHeaderAccessor.wrap(message);

将获得 header 的克隆，您必须使用新的克隆 header 创建新消息

下面是完整的固定代码

@Override
      public Message<?> preSend(Message<?> message, MessageChannel channel) {

        StompHeaderAccessor accessor = MessageHeaderAccessor.getAccessor(message, StompHeaderAccessor.class);
       // StompHeaderAccessor accessor = StompHeaderAccessor.wrap(message);
        if(accessor != null) {
            StompCommand command = accessor.getCommand();
            if(command != null) {
                log.debug("Receiving msg {} from {}",command,accessor.getUser().getName());
                if(command == StompCommand.SEND) {

                    log.debug("Adding expires header to  msg {} from {}",command,accessor.getUser().getName());
                    String ttlString = accessor.getFirstNativeHeader("ttl");
                    long ttl = 30000;
                    if(ttlString != null) {
                        try {
                            ttl = Long.parseLong(ttlString);
                        } 
                        catch(Exception ex) {
                            log.error("TTL header received but not in correct format {}",ttlString);
                        }
                    }

                    accessor.addNativeHeader("expires", Long.toString(System.currentTimeMillis() + ttl));
                     // I don't need any more to create a new message
                    //return MessageBuilder.createMessage(message.getPayload(), accessor.getMessageHeaders());
                }
            }
        }
        return message;
      }