I'm not sure how your approach works, but since it looks like you're using
Java reflection, my guess is that it will only work with compiled-in
services.  If your code is a library, this will prevent users of that
library from using dynamic types, which is unfortunate.  If the users
provide a default instance, then they can choose to provide either a
compiled-in type or a dynamic type.

On Tue, Feb 23, 2010 at 1:55 PM, ph <pkirsa...@gmail.com> wrote:

> Thanks Kenton,
>
> I was using getRequestPrototype, but I need an actual instance of
> Service to call that method that created additional extra dependency
> in my code that why I started to look for alternatives. I know my
> method name and currently I'm just parsing response (byte array) this
> way (in Scala):
> Class.forName ( String.format ( classNameFormat, methodName ) )
>        .getDeclaredMethod ( "parseFrom", Array ( msg.getClass ) : _* )
>        .invoke ( null, Array ( msg ) : _* ).asInstanceOf
> [ com.google.protobuf.GeneratedMessage ]
> This works fine. I will try to use a Default Message or
> DynamicMessage, thanks for suggestion. From the top of your head, do
> you think DynamicMessage will be faster or slower than my approach?
>
>
> On Feb 22, 6:10 pm, Kenton Varda <ken...@google.com> wrote:
> > Right, Descriptor.toProto() returns a DescriptorProto, which is itself a
> > protobuf type.  So, calling newBuilderForType() on that is going to
> return a
> > builder for DescriptorProto, not a builder for the type described.
> >
> > What you want is com.google.protobuf.DynamicMessage.
> >
> > Note that DynamicMessage is slower than the message classes produced by
> > protoc.  So if the type in question is actually compiled in to your app,
> you
> > should use it instead.  Typically what you'd do is pass around the type's
> > default instance (MyMessageType.getDefaultInstance()) instead of passing
> > around the descriptor.
> >
> > Note that the Service interface also provides a method
> > getRequestPrototype(MethodDescriptor) which returns the default instance
> for
> > the type, on which you can then call newBuilderForType().
> >
> >
> >
> > On Sat, Feb 20, 2010 at 12:54 PM, ph <pkirsa...@gmail.com> wrote:
> > > I'm trying to build service return message using
> > > Descriptors.ServiceDescriptor.
> > > This does not work:
> > > serviceDescriptor.findMethodByName
> > > ( methodName ).getOutputType.toProto.newBuilderForType.mergeFrom
> > > ( msg ).build
> > > "msg" is byte array
> > > It builds DesscriptorProtos.DescriptorProto instead of Message.
> >
> > > Is there a way to build message from byte array using method
> > > descriptor?
> >
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