Pipeline configuration: Decoder, Handler, Encoder - throws: UnsupportedOperationException: unsupported message type: DefaultHttpResponse (expected: ByteBuf, FileRegion)

Expected behavior

The pipeline configuration:

• Decoder
• Handler
• Encoder should not throw exception when a client sends HTTP request.

By reading the documentation, the order should be executed like so:

Inbound: Decoder, Handler

Outbound: Encoder

Actual behavior

The pipeline thorws exception:

Aug 14, 2022 2:14:04 PM io.netty.channel.DefaultChannelPipeline onUnhandledInboundException
WARNING: An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception.
java.lang.UnsupportedOperationException: unsupported message type: DefaultHttpResponse (expected: ByteBuf, FileRegion)

Steps to reproduce

• Clone my repo: https://github.com/ShlomiRex/netty-pipeline-test
• Run the code with the pipeline configuration:
• Send dummy HTTP request: curl -v 127.0.0.1:8080
• The program throws exception.
• Uncomment the ‘Works’ section, and comment the ‘Doesn’t work’ section and see that it works, but not the other way around.

Minimal yet complete reproducer code (or URL to code)

https://github.com/ShlomiRex/netty-pipeline-test

Netty version

4.1.10.Final

JVM version (e.g. java -version)

11

OS version (e.g. uname -a)

• macOS 12.6, macbook pro 16 M1
• Linux CentOS

[chrisvest]

If your handler does a write to the ChannelHandlerContext it’s passed in, say, channelRead, then the write will propagate up from the handlers position in the pipeline. Otherwise handlers wouldn’t have a way to pass the write through.

If you do a write to the Channel, then it’ll propagate from the bottom of the pipeline.

[ShlomiRex]

If your handler does a write to the ChannelHandlerContext it’s passed in, say, channelRead, then the write will propagate up from the handlers position in the pipeline. Otherwise handlers wouldn’t have a way to pass the write through.

If you do a write to the Channel, then it’ll propagate from the bottom of the pipeline.

Thanks a lot! If I change ctx.write() to ctx.channel.write() it propogates to the next pipeline as expected! And so the code:

                            pipeline.addLast(new HttpRequestDecoder());
                            pipeline.addLast(new MyHandler());
                            pipeline.addLast(new HttpResponseEncoder());

works! (it didn’t work before because I was writing to context, and not channel).

Your a life savior!