Hi Kenton,

That seems to be working well. I used mergeFrom(inputStream) on the
builder as below which looks the simplest way (I will add in an
isInitialized check)


Thanks for the help,


On Nov 1, 8:55 pm, Kenton Varda <ken...@google.com> wrote:
> What you want to do is create a Map<Descriptor, Message> which maps from
> descriptors to default instances of each of your generated classes.  For
> example:
>   Map<Descriptor, Message> myMap = new ...;
>   myMap.put(FooMessage.getDescriptor(), FooMessage.getDefaultInstance());
>   myMap.put(BarMessage.getDescriptor(), BarMessage.getDefaultInstance());
>   myMap.put(BazMessage.getDescriptor(), BazMessage.getDefaultInstance());
> Now when you have a descriptor desc and you want to create a Builder for
> that type, you do:
>   Message.Builder builder = myMap.get(desc).newBuilderForType();
> When you call builder.build(), you will end up with a Message that can be
> down-cast to your generated type.
> DynamicMessage is meant to be used for types that aren't compiled in at all.
>  So of course you can't cast from DynamicMessage to a generated class -- the
> generated classes are not subclasses of DynamicMessage.
> On Sat, Oct 31, 2009 at 7:57 AM, Martin Gilday <martingil...@gmail.com>wrote:
> > I am trying to write a service in Java which will convert back and
> > forth using protobufs.  The docs say that this should be easy as
> > "Reflection is provided as part of the Message and Message.Builder
> > interfaces".  However I cannot seem to find what this is referring to.
> > I would like have a generic method which takes a Descriptor and a
> > stream which gives back an instance of message which I can later cast
> > to my desired type.  I have tried DynamicMessage from =
> > DynamicMessage.parseFrom(descriptor, inputStream); but I get an
> > exception when I attempt to cast this as my generate proto class.
> > Is there a solution to this?
> > Thanks,
> > Martin.
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