CODEWITHSUNDEEP
javaprotocol-buffersproto
rascio
rascio

Reputation: 9279

Protobuf java create a Descriptor from DescriptorProto

I was looking for a way to create from a com.google.protobuf.DescriptorProtos.DescriptorProto a com.google.protobuf.Descriptors.Descriptor

Like doing:

var descProto = DescriptorProtos.DescriptorProto.newBuilder()
            .setName("MyDynamicType")
            .addField(DescriptorProtos.FieldDescriptorProto.newBuilder()
                .setName("my_dynamic_field")
                .setType(DescriptorProtos.FieldDescriptorProto.Type.TYPE_STRING)
            )
            .build()
Descriptors.Descriptor descriptor = theResponseToThisQuestion(descProto)

P.S. I'm start to thinking that it is not possible, as this function would be the protobuf compiler itself, and it is built to output .java files, so cannot be called at runtime

Upvotes: 2

Views: 3402

Answers (1)

Rafael Lerm
Rafael Lerm

Reputation: 1400

The issue is that message descriptors often depend on other messages, possibly defined in other files. So the top-level entry point for the library is FileDescriptor and FileDescriptorProto.

In the case where the message is self-contained (only primitive fields), it should be easy to just wrap the DescriptorProto using something like:

Descriptor standaloneMessage(DescriptorProto message) 
    throws DescriptorValidationException {
  FileDescriptorProto file = FileDescriptorProto.newBuilder()
      .setName("synthetic_file.proto")
      .addMessageType(message)
      .build();
  FileDescriptor file = FileDescriptor.buildFrom(file, new FileDescriptorProto[]{});
  return file.findMessageTypeByName(message.getName());
}

Upvotes: 5

Related Questions