Typecasting Problem Using Netty and Google Protobuf

["이희승 (Trustin Lee)"]

Hi Akash,

Could you show us the bootstrap code (e.g. main()) of the receiving 
part?  I suspect that your pipeline does not have proper decoders.

HTH

Akash Gangil wrote:
> *
> Hi,
>
> Explaining the problem in nutshell when I typecast the message (received
> by the client) to the message type (of protocol buffer class) in the
> server I get this error WARNING: Unexpected exception from downstream.
> java.lang.ClassCastException:
> org.jboss.netty.buffer.BigEndianHeapChannelBuffer cannot be cast to
> org.jboss.netty.example.echo.MessageProtos$Packet
> **
> *
> Packet p = (Packet) e.getMessage() ,
> *
> **
> where Packet is the Message class generated via google Proc Buffers
> **
>
> *
> *
> *
> *SGClienthandler.java : *
> *
> *
>
>     public void send(String message_type, String message_to_send, int
>     message_id){
>     Packet p = Packet.newBuilder()
>     .setPacketId(message_id)
>     .setPacketType(message_type)
>             .setPacketContent(message_to_send).build();
>     try {
>                  channel.write(p);
>                  System.out.print("Message was sent to this channel : "
>     + channel);
>     }
>     catch (Exception e) {
>     System.out.println(" In send() ");
>     e.printStackTrace();
>     }
>     }
>
> *EchoServerhandler.java :*
>
>       @Override
>            public void messageReceived(
>                    ChannelHandlerContext ctx, MessageEvent e) {
>       System.out.print("Message Received : " + e.getMessage());
>       Packet req = (Packet) e.getMessage();
>       System.out.print("Packet Id received  : " + req.getPacketId());
>       System.out.print("Packet Type received  : " + req.getPacketType());
>       System.out.print("Packet Content received  : " +
>     req.getPacketContent());
>     }
>
>
>
> The Pipeline factory of both the client and server namely  :
> *SGPipelineFactory and EchoServerPipelineFactory *have same
> encoding and decoding handlers apart from the specific handlers related
> to their logic.
>
>           // Decoders
>              pipeline.addLast("frameDecoder", new
>     ProtobufVarint32FrameDecoder());
>              pipeline.addLast("protobufDecoder", new
>     ProtobufDecoder(Packet.getDefaultInstance()));
>
>              // Encoder
>              pipeline.addLast("frameEncoder", new
>     ProtobufVarint32LengthFieldPrepender());
>              pipeline.addLast("protobufEncoder", new ProtobufEncoder());
>
>
>
>
> *Error :*
>
>     WARNING: Unexpected exception from downstream.
>     java.lang.ClassCastException:
>     org.jboss.netty.buffer.BigEndianHeapChannelBuffer cannot be cast to
>     org.jboss.netty.example.echo.MessageProtos$Packet
>     at
>     org.jboss.netty.example.echo.EchoServerHandler.messageReceived(EchoServerHandler.java:63)
>
>     The line 63 is in red.
>
>
>     Would be great if I can get some pointers.
>
> --
> Akash
>
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-- 
Trustin Lee, http://gleamynode.net/