Decoding binary data from TCP to XML in JBoss Fuse - tcp

Question

I'm new to ESBs in general, however I've been tasked to implement a TCP reader which outputs XML data in JBoss Fuse. I've tried a few methods, with limited success so far.
I started by using the Camel Blueprint ArchType (since that's what most of the Fuse tutorials are based around). I then defined a simple route beginning with a Netty4 input, running through a custom decoder class and logging the result.
blueprint.xml
<?xml version="1.0" encoding="UTF-8"?>
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.osgi.org/xmlns/blueprint/v1.0.0 http://www.osgi.org/xmlns/blueprint/v1.0.0/blueprint.xsd
http://camel.apache.org/schema/blueprint http://camel.apache.org/schema/blueprint/camel-blueprint.xsd">
<bean id="myMessageDecoder" class="com.mycompany.binaryreceiver.binaryreceiver.MyMessageDecoder" />
<camelContext allowUseOriginalMessage="false" xmlns="http://camel.apache.org/schema/blueprint">
<route>
<from uri="netty4:tcp://localhost:9999?decoder=#myMessageDecoder&sync=false"/>
<log message="Message Received: ${body}"/>
</route>
</camelContext>
</blueprint>
MyMessageDecoder.java
package com.mycompany.binaryreceiver.binaryreceiver;
import java.util.List;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.ByteToMessageDecoder;
public class MyMessageDecoder extends ByteToMessageDecoder {
#Override
protected void decode(ChannelHandlerContext context, ByteBuf buffer, List<Object> out) throws Exception {
if (buffer.readableBytes() < 3) {
return;
}
byte[] bytes = new byte[3];
buffer.readBytes(bytes);
MyMessage myMessage = new MyMessage(bytes);
out.add(myMessage);
}
}
MyMessage.java
package com.mycompany.binaryreceiver.binaryreceiver;
public class MyMessage {
protected int data1;
protected int data2;
protected int data3;
public MyMessage(byte[] data) {
data1 = data[0];
data2 = data[1];
data3 = data[2];
}
public String toString() {
return "MyMessage: { " + this.data1 + ", " + this.data2 + ", " + this.data3 + " }";
}
}
The decoder simply checks if there are three bytes on the buffer. If there is, then it pushes these bytes into MyMessage, which offers a toString interface which the logger can access.
Obviously this is just an example, and the final message is much more complex, involving variable length content, however this illustrates the basic process.
This all appears to work, if I push a stream of bytes into port 9999, the logger outputs the expected values:
INFO Message Received: MyMessage: { 1, 13, 58 }
INFO Message Received: MyMessage: { 2, 36, 63 }
INFO Message Received: MyMessage: { 3, 74, 5 }
INFO Message Received: MyMessage: { 4, 12, 92 }
INFO Message Received: MyMessage: { 5, 111, -121 }
INFO Message Received: MyMessage: { 6, 0, 0 }
INFO Message Received: MyMessage: { 7, 80, 64 }
INFO Message Received: MyMessage: { 8, 0, 0 }
INFO Message Received: MyMessage: { 9, 0, -116 }
INFO Message Received: MyMessage: { 10, -108, 111 }
INFO Message Received: MyMessage: { 11, -17, -100 }
INFO Message Received: MyMessage: { 12, -35, -28 }
However, during startup I'm getting the following message:
[Blueprint Extender: 1] NettyConfiguration WARN
The decoder com.mycompany.binaryreceiver.binaryreceiver.MyMessageDecoder#2413a0f1
is not #Shareable or an ChannelHandlerFactory instance. The decoder cannot safely be used.
After looking up the warning, I found references which seemed to suggest that I'm going around the whole process incorrectly, and that I should be going through the Netty4 ChannelHandlerFactories.
Has anyone got experience of performing a similar binary -> XML process who can comment or assist with the correct/recommended process for performing these tasks?
Is the warning a legitimate problem, or a red herring? Should I be utilising the ChannelHandlerFactories, or a completely different approach?

Answer 1

See the camel-netty4 documentation, at the section about non shareable encoders or decoders. Its all documentation what you have to do:
http://camel.apache.org/netty4

Answer 2

I was planning to implement a factory in order to try and handle the instantiation of the decoders; however, I was lucky and the functionality I actually needed could be implemented with the built-in length field decoder.
<bean id="lengthFieldDecoder"
class="org.apache.camel.component.netty4.ChannelHandlerFactories"
factory-method="newLengthFieldBasedFrameDecoder">
<argument value="10000" /> <!-- Max Frame Length -->
<argument value="0" /> <!-- Length Field Offset -->
<argument value="4" /> <!-- Length Field Length -->
<argument value="0" /> <!-- Length Adjustment -->
<argument value="4" /> <!-- Initial Bytes to Strip -->
</bean>
<camelContext trace="false" xmlns="http://camel.apache.org/schema/blueprint">
<route>
<from uri="netty4:tcp://localhost:9999?decoder=#lengthFieldDecoder&
clientMode=true&sync=false"
id="Netty4 TCP Client" />
<log message="Message (Binary): ${body}" id="Log Binary"/>
</route>
</camelContext>