decoding a PUT request in Netty

Question

I have created an HTTPServer in Netty with the following handler:

public class HttpRouterServerHandler extends SimpleChannelInboundHandler<HttpRequest> {

public void channelRead0(ChannelHandlerContext ctx, HttpRequest req) {
  if (HttpUtil.is100ContinueExpected(req)) {
     ctx.writeAndFlush(new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.CONTINUE));
     return;
  }

  System.out.println(req.toString());
  HttpResponse res = /* create the response here */      
  flushResponse(ctx, req, res);
}

I send the PUT request in Python using http.client:

     json_data = /* constructJSON content */
     connection = http.client.HTTPConnection("localhost", 8080)
     connection.request("PUT", "/proto/api/send", json_data)     
     response = self.connection.getresponse()
     connection.close()

For some reason, I can't get the BODY of the request (the json content). The reason seems to be that my HttpRequest is not a FullHttpRequest, so I can't get its content()

It I print the content of my request, I have something like:

DefaultHttpRequest(decodeResult: success, version: HTTP/1.1)
PUT /proto/api/send HTTP/1.1
Host: localhost:8080
Accept-Encoding: identity
content-length: 47

Also I tried to replace the HttpRequest by FullHttpRequest for my handler, but in this case the Netty server does not respond anymore, which lead to an exception in Python:

public class HttpRouterServerHandler extends SimpleChannelInboundHandler<FullHttpRequest> {

  public void channelRead0(ChannelHandlerContext ctx, FullHttpRequest req) {
    if (HttpUtil.is100ContinueExpected(req)) {
       ctx.writeAndFlush(new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.CONTINUE));
    return;
  } 

   System.out.println(req.toString());
   HttpResponse res = /* create the response here */      
   flushResponse(ctx, req, res);
}

Where is my mistake?

score 1 · Answer 1 · answered Jul 23 '21 at 17:04

1

If you do not use FullHttpRequest, you will get the following messages:

One HttpRequest message
Zero or more HttpContent messages
One LastHttpContent message

The issue with the first code snippet is that it is only accepting HttpRequest, if you want to get all the above messages, you should accept HttpObject.

I am not sure what is wrong with the second snippet, most likely you are not receiving the entire content hence FullHttpRequest is not created and emitted. I will suggest adding a LoggingHandler to the pipeline and see what you receive on the wire.

answered Jul 23 '21 at 17:04

Nitesh Kant

136
3

Thanks, I will do that ASAP!! – Hervé Girod Jul 23 '21 at 17:15
Thanks again, your remarks helped me to understand my mistake (see the answer below). – Hervé Girod Jul 27 '21 at 14:05

score 0 · Accepted Answer · answered Jul 27 '21 at 14:04

My error was in the initializer. I did:

public class HttpRouterServerInitializer extends ChannelInitializer<SocketChannel> {
  private final HttpRouterServerHandler handler;

  public HttpRouterServerInitializer(HttpPythonModule module) {
     handler = new HttpRouterServerHandler(moduler);
  }

  public void initChannel(SocketChannel ch) {
     ch.pipeline()
        .addLast(new HttpServerCodec())
        .addLast(handler)
  }
}

where I should have done:

public class HttpRouterServerInitializer extends ChannelInitializer<SocketChannel> {
  private final HttpRouterServerHandler handler;

  public HttpRouterServerInitializer(HttpPythonModule module) {
     handler = new HttpRouterServerHandler(moduler);
  }

  public void initChannel(SocketChannel ch) {
     ch.pipeline()
        .addLast(new HttpServerCodec())
        .addLast(new HttpObjectAggregator(Integer.MAX_VALUE))
        .addLast(handler)
  }
}

The Netty documentation says about the HttpObjectAggregator class:

A ChannelHandler that aggregates an HttpMessage and its following HttpContents into a single FullHttpRequest or FullHttpResponse (depending on if it used to handle requests or responses) with no following HttpContents.

For information I did not show this part of the code before because I did not think this was remotely connected to my problem. Turned out it was the reason of my problem :) — Hervé Girod, Jul 28 '21 at 10:44

decoding a PUT request in Netty

2 Answers2