DescriptorProto.getDescriptorForType() returns the Descriptor for
DescriptorProto, not for the type which that DescriptorProto is describing.
Remember that DescriptorProto is just a protocol message like any other --
it does not have any special methods that recognize its higher-level
meaning.
To convert DescriptorProtos to Descriptors, you need to use
FileDescriptor.buildFrom().
On Sun, Mar 21, 2010 at 5:20 PM, Kevin Tambascio
<kevin.tambas...@gmail.com>wrote:
> Hi,
>
> I'm having trouble getting the following code to work. Using
> protoc.exe, I generated a file with the descriptor data using the --
> descriptor_set_out file. I've written some Java code to read the
> file, and try to instantiate a default instance of one of the objects
> in the descriptor, so that I write it out to an XML file using the
> protobuf-format-java library.
>
> Here's my code. The variable "descriptorData" contains the binary
> content of the descriptor file, without any modifications:
>
> DescriptorProtos.FileDescriptorSet fdSet =
> FileDescriptorSet.newBuilder().mergeFrom(descriptorData).build();
> FileDescriptorProto fdp = fdSet.getFile(0);
>
> List<DescriptorProto> messageTypes =
> fdp.getMessageTypeList();
> for(DescriptorProto type : messageTypes)
> {
> System.out.println("Type is: " + type.getName());
> FileDescriptor fd =
> type.getDescriptorForType().getFile();
>
> DynamicMessage dm =
> DynamicMessage.getDefaultInstance(type.getDescriptorForType());
> System.out.println(XmlFormat.printToString(dm));
> }
>
> I've tried numerous combinations of the above code, but each time I
> get the following output:
>
> Type is: Type1
> <DescriptorProto></DescriptorProto>
> Type is: Type2
> <DescriptorProto></DescriptorProto>
> Type is: Type3
> <DescriptorProto></DescriptorProto>
> Type is: Type4
> <DescriptorProto></DescriptorProto>
> Type is: Type5
> <DescriptorProto></DescriptorProto>
> Type is: Type6
> <DescriptorProto></DescriptorProto>
>
> The proto file has Type1, Type2, Type3, etc, defined as messages. The
> fact that type.getName() does return the type names from my proto
> file, leads me to believe I'm heading in the right direction.
> However, the DynamicMessage type that is created (and serialized to
> XML) seems to indicate that I'm not passing the right descriptor
> instance in to create the object.
>
> Any thoughts?
>
> Thanks,
> Kevin
>
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