Hi again :)<div><br></div><div>Made a quick example of doing the same thing Trustin just demonstrated, by using the protobuf union type/wrapper trick. Should note that protobuf does not (and can not be made to) generate any code to provide easy handling for this approach, so its a bit cumbersome. Okay, to the example, lets say you want to send the messages Foo and Bar. The trick is to define a "union type" or a sort of a container that you put your actual message inside:</div>
<div><br></div><div><div>message Foo{</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>optional string some_field = 1;</div><div>}</div><div><br></div><div>message Bar{</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>optional string some_other_field = 1;</div>
<div>}</div><div><br></div><div><br></div><div>message MessageWrapper{</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>enum Type {FOO = 1; BAR = 2; }</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>required Type type = 1;</div>
<div><br></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>optional Foo foo = 2;</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>optional Bar bar = 3;</div><div>}</div><div><br>
</div><div><br></div><div>So when you want to send a Foo message, you construct the Foo message as usual, and then wrap it inside a MessageWrapper mesage. You then have to adhere to the convention, that always</div><div> 1) Set just one of the optional fields</div>
<div> 2) Set the Type field to the enum representing that field.</div><div><br></div><div>For example to send Foo:</div><div><br></div><div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Foo fooMsg = </div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>Foo.newBuilder().</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>setSomeField("SomeValue").</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>build();</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>MessageWrapper wrapperMsg = </div><div><span class="Apple-tab-span" style="white-space:pre"> </span>MessageWrapper.newBuilder().</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>setType(Type.FOO).</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>setFoo(fooMsg).</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>build();</div>
<div><br></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>someChannel.write(wrapperMsg);</div><div><br></div><div>Note: It's important that you always remember to wrap the messages you send, otherwise you get a very strange behavior. </div>
<div><br></div><div>You then setup your pipeline with a handler to receive this wrapper message:</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>p.addLast("protobufDecoder", new ProtobufDecoder(MessageWrapper.getDefaultInstance()));</div>
<div><br></div><div>and in your application specific handler do something like:</div><div><br></div><div><div><span class="Apple-tab-span" style="white-space:pre"> </span>public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>MessageWrapper wrapperMsg = (MessageWrapper)e.getMessage();</div><div><span class="Apple-tab-span" style="white-space:pre"> </span></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>switch (wrapperMsg.getType()){</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>case FOO:</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Foo fooMsg = wrapperMsg.getFoo();</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>//Handle a Foo message</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>break;</div><div><span class="Apple-tab-span" style="white-space:pre"> </span></div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>case BAR:</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Bar barMsg = wrapperMsg.getBar();</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>//Handle a Bar message</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>break;</div><div><span class="Apple-tab-span" style="white-space:pre"> </span></div><div><span class="Apple-tab-span" style="white-space:pre"> </span></div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span>default:</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>throw new IllegalArgumentException("..... Type: " + wrapperMsg.getType());</div>
<div><span class="Apple-tab-span" style="white-space:pre"> </span></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>}</div><div><span class="Apple-tab-span" style="white-space:pre"> </span></div><div>
<span class="Apple-tab-span" style="white-space:pre"> </span>}</div></div></div></div><div><br></div><div><br></div><div>Hope this helps. Will see if I can find time to put a complete sample together. </div><div><br></div>
<div>Regards</div><div>Jannick</div><div><br><br><div class="gmail_quote">2010/1/7 "Trustin Lee (이희승)" <span dir="ltr"><<a href="mailto:trustin@gmail.com">trustin@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Tom,<br>
<br>
I would write a custom decoder instead of using ProtobufDecoder in such<br>
a case; something like the following, which prepends the message type<br>
and the message length field:<br>
<br>
public class MyProtobufDecoder extends FrameDecoder {<br>
<br>
boolean waitingForHeader;<br>
int msgType;<br>
int msgLength;<br>
<br>
Message prototypeA =<br>
MessageA.getDefaultInstance().getDefaultInstanceForType();<br>
Message prototypeB =<br>
MessageB.getDefaultInstance().getDefaultInstanceForType();<br>
Message prototypeC =<br>
MessageC.getDefaultInstance().getDefaultInstanceForType();<br>
<br>
@Override<br>
protected Object decode(ctx, msg) {<br>
ChannelBuffer buf = (ChannelBuffer) msg;<br>
if (waitingForHeader) {<br>
// Wait until at least 5 bytes are received in the buffer<br>
if (buf.readableBytes() < 5) {<br>
return null;<br>
}<br>
msgType = buf.readByte();<br>
msgLength = buf.readInt();<br>
waitingForHeader = false;<br>
}<br>
<br>
if (!waitingForHeader) {<br>
ChannelBuffer pbmsg = buf.readBytes(msgLength);<br>
Message prototype;<br>
switch (msgType) {<br>
case 0: prototype = prototypeA; break;<br>
case 1: prototype = prototypeB; break;<br>
case 2: prototype = prototypeC; break;<br>
<br>
// This is a user defined exception.<br>
// Handle this exception in exceptionCaught()<br>
// in your terminal handler<br>
default: throw new ProtocolViolationException();<br>
}<br>
<br>
try {<br>
return prototype.newBuilderForType().mergeFrom(<br>
new ChannelBufferInputStream(pbmsg)).build();<br>
} finally {<br>
waitingForHeader = true;<br>
}<br>
}<br>
}<br>
}<br>
<br>
You will have to learn how to write a decoder eventually to customize<br>
the protocol to meet your need. The user guide and the factorial<br>
example is a good starting point.<br>
<br>
However, I would still recommend the solution Jannick provided.<br>
<br>
HTH,<br>
<font color="#888888">Trustin<br>
</font><div><div></div><div class="h5"><br>
ritom wrote:<br>
> Thanks for very much for the insight. If you do have multiple messages how to<br>
> you handle them in the decoder. In the example looks like everything is<br>
> based on one object what if you have two message type Foo and Bar instead of<br>
> LocalTimeProtocol alone. Can you please give a example. Thanks a lot in<br>
> advance.<br>
><br>
> p.addLast("protobufDecoder", new<br>
> ProtobufDecoder(LocalTimeProtocol.Locations.getDefaultInstance()));<br>
><br>
><br>
> Thingfish wrote:<br>
>> Hi<br>
>><br>
>> The easiest solution is to wrap all your messages in a 'union type' as<br>
>> described in this protobuf tutorial:<br>
>> <a href="http://code.google.com/intl/da-DK/apis/protocolbuffers/docs/techniques.html#union" target="_blank">http://code.google.com/intl/da-DK/apis/protocolbuffers/docs/techniques.html#union</a><br>
>><br>
>> Alternatively you will have to manually prepend some kind of command id to<br>
>> identity the kind of protobuf message being sent, but unlikely to be worth<br>
>> the trouble.<br>
>><br>
>><br>
>> Regards<br>
>> Jannick<br>
>> <<a href="http://code.google.com/intl/da-DK/apis/protocolbuffers/docs/techniques.html#union" target="_blank">http://code.google.com/intl/da-DK/apis/protocolbuffers/docs/techniques.html#union</a>><br>
>><br>
>> 2010/1/2 ritom <<a href="mailto:ritom@hotmail.com">ritom@hotmail.com</a>><br>
>><br>
>>> Can somebody please help me understand the google protobuf support within<br>
>>> Netty.<br>
>>> In the LocalTimeServerPipelineFactory example we have<br>
>>><br>
>>> p.addLast("protobufDecoder", new<br>
>>> ProtobufDecoder(LocalTimeProtocol.Locations.getDefaultInstance()));<br>
>>><br>
>>> That would mean we can now receive the Locations message in<br>
>>> TimeServerHandler.<br>
>>><br>
>>> public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) {<br>
>>> Locations locations = (Locations) e.getMessage();<br>
>>><br>
>>> How would I implement support for multiple incoming message types where<br>
>>> you<br>
>>> might be receiving different types of request from the client. Lets say<br>
>>> you<br>
>>> are receiving Logon first then BalanceRequest, TransferRequest and so on.<br>
>>> Also server will reply with multiple Message Types depending on the<br>
>>> request.<br>
>>> Can somebody please please help.<br>
>>><br>
>>> Tom<br>
>>> --<br>
>>> View this message in context:<br>
>>> <a href="http://n2.nabble.com/Google-protocol-Buffer-Codec-tp4241485p4241485.html" target="_blank">http://n2.nabble.com/Google-protocol-Buffer-Codec-tp4241485p4241485.html</a><br>
>>> Sent from the Netty User Group mailing list archive at Nabble.com.<br>
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>><br>
>><br>
><br>
<br>
--<br>
</div></div><div><div></div><div class="h5">what we call human nature in actuality is human habit<br>
<a href="http://gleamynode.net/" target="_blank">http://gleamynode.net/</a><br>
<br>
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