How to get protobuf extension field in ProtobufAnnotationSerializer - protocol-buffers

Question

I am a new to protocol-buffers and try to figure out how to extend a message type in the Stanford CoreNLP library as described here: https://nlp.stanford.edu/nlp/javadoc/javanlp/edu/stanford/nlp/pipeline/ProtobufAnnotationSerializer.html
The problem: I can set the extension field but i can't get it. I boiled the problem down to the code below. In the original message the field name is [edu.stanford.nlp.pipeline.myNewField] but is replaced by the field number 101 in the deserialized message.
How can i get the value of myNewField?
PS: This post https://stackoverflow.com/questions/28815214/how-to-set-get-protobufs-extension-field-in-go suggests that it should be as easy as calling getExtension(MyAppProtos.myNewField)
custom.proto
syntax = "proto2";
package edu.stanford.nlp.pipeline;
option java_package = "com.example.my.awesome.nlp.app";
option java_outer_classname = "MyAppProtos";
import "CoreNLP.proto";
extend Sentence {
optional uint32 myNewField = 101;
}
ProtoTest.java
import com.example.my.awesome.nlp.app.MyAppProtos;
import com.google.protobuf.ExtensionRegistry;
import com.google.protobuf.InvalidProtocolBufferException;
import edu.stanford.nlp.pipeline.CoreNLPProtos;
import edu.stanford.nlp.pipeline.CoreNLPProtos.Sentence;
public class ProtoTest {
static {
ExtensionRegistry registry = ExtensionRegistry.newInstance();
registry.add(MyAppProtos.myNewField);
CoreNLPProtos.registerAllExtensions(registry);
}
public static void main(String[] args) throws InvalidProtocolBufferException {
Sentence originalSentence = Sentence.newBuilder()
.setText("Hello world!")
.setTokenOffsetBegin(0)
.setTokenOffsetEnd(12)
.setExtension(MyAppProtos.myNewField, 13)
.build();
System.out.println("Original:\n" + originalSentence);
byte[] serialized = originalSentence.toByteArray();
Sentence deserializedSentence = Sentence.parseFrom(serialized);
System.out.println("Deserialized:\n" + deserializedSentence);
Integer myNewField = deserializedSentence.getExtension(MyAppProtos.myNewField);
System.out.println("MyNewField: " + myNewField);
}
}
Output:
Original:
tokenOffsetBegin: 0
tokenOffsetEnd: 12
text: "Hello world!"
[edu.stanford.nlp.pipeline.myNewField]: 13
Deserialized:
tokenOffsetBegin: 0
tokenOffsetEnd: 12
text: "Hello world!"
101: 13
MyNewField: 0
Update
Because this question was about extending CoreNLP message types and using them with the ProtobufAnnotationSerializer, here is what my extended serializer looks like:
import java.io.IOException;
import java.io.InputStream;
import java.util.Set;
import com.example.my.awesome.nlp.app.MyAppProtos;
import com.google.protobuf.ExtensionRegistry;
import edu.stanford.nlp.pipeline.Annotation;
import edu.stanford.nlp.pipeline.CoreNLPProtos;
import edu.stanford.nlp.pipeline.CoreNLPProtos.Sentence;
import edu.stanford.nlp.pipeline.CoreNLPProtos.Sentence.Builder;
import edu.stanford.nlp.pipeline.ProtobufAnnotationSerializer;
import edu.stanford.nlp.util.CoreMap;
import edu.stanford.nlp.util.Pair;
public class MySerializer extends ProtobufAnnotationSerializer {
private static ExtensionRegistry registry;
static {
registry = ExtensionRegistry.newInstance();
registry.add(MyAppProtos.myNewField);
CoreNLPProtos.registerAllExtensions(registry);
}
#Override
protected Builder toProtoBuilder(CoreMap sentence, Set<Class<?>> keysToSerialize) {
keysToSerialize.remove(MyAnnotation.class);
Builder builder = super.toProtoBuilder(sentence, keysToSerialize);
builder.setExtension(MyAppProtos.myNewField, 13);
return builder;
}
#Override
public Pair<Annotation, InputStream> read(InputStream is)
throws IOException, ClassNotFoundException, ClassCastException {
CoreNLPProtos.Document doc = CoreNLPProtos.Document.parseDelimitedFrom(is, registry);
return Pair.makePair(fromProto(doc), is);
}
#Override
protected CoreMap fromProtoNoTokens(Sentence proto) {
CoreMap result = super.fromProtoNoTokens(proto);
result.set(MyAnnotation.class, proto.getExtension(MyAppProtos.myNewField));
return result;
}
}

Answer 1

The mistake was that i didn't provide the parseFrom call with the extension registry.
Changing Sentence deserializedSentence = Sentence.parseFrom(serialized); to Sentence deserializedSentence = Sentence.parseFrom(serialized, registry); did the job!