io.netty.util.Attribute#compareAndSet ( )源码实例Demo

@Override
public <T> T getAttribute(final String key, final Function<String, T> function) {
    if (key == null) {
        return null;
    }
    Attribute<T> attribute = channel.attr(AttributeKey.valueOf(key));
    T result = attribute.get();
    if (result == null && function != null) {
        T target = function.apply(key);
        if (target != null) {
            if (attribute.compareAndSet(null, target)) {
                return target;
            } else {
                return attribute.get();
            }
        }
    }
    return result;
}
 

@Override public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise prm) {
  Attribute<Span> spanAttr = ctx.channel().attr(NettyHttpTracing.SPAN_ATTRIBUTE);
  Span span = spanAttr.get();
  spanAttr.compareAndSet(span, null);
  if (span == null || !(msg instanceof HttpResponse)) {
    ctx.write(msg, prm);
    return;
  }

  HttpResponse response = (HttpResponse) msg;

  Scope scope = currentTraceContext.maybeScope(span.context());
  Throwable error = null;
  try {
    ctx.write(msg, prm);
  } catch (Throwable t) {
    error = t;
    throw t;
  } finally {
    HttpServerRequest request = ctx.channel().attr(NettyHttpTracing.REQUEST_ATTRIBUTE).get();
    handler.handleSend(new HttpResponseWrapper(request, response, error), span);
    scope.close();
  }
}
 

public void put(UUID recId, ChannelHandlerContext ctx) {
   if(ctx == null) {
      return;
   }
   Attribute<UUID> recIdAttr = ctx.attr(REC_KEY);
   if(!recIdAttr.compareAndSet(null, recId)) {
      throw new IllegalStateException("attempt to set existing non-null ctx recId [" + recIdAttr.get() + "] to [" + recId + "]");
   }
   sessions.put(recIdAttr.get(), ctx);
}
 

public static ChannelTransport getOrNewTransport(Channel channel, RequestBarrier requestBarrier) {
    Attribute<ChannelTransport> attr = channel.attr(TRANSPORT_CACHE_ATTR);
    ChannelTransport transport = attr.get();

    if (transport == null) {
        transport = newTransport(channel, requestBarrier);
        if (!attr.compareAndSet(null, transport)) {
            transport = attr.get();
        }
    }

    return transport;
}
 

/**
 * 添加新的会话
 * @param channel
 * @param session
 * @return
 */
public static boolean addChannelSession(Channel channel, IdSession session) {
	Attribute<IdSession> sessionAttr = channel.attr(SESSION_KEY);
	return sessionAttr.compareAndSet(null, session);
}