Protobuf Descriptor and Dynamic Messages

HelloProto.java

package org.hello.protobuf;

import java.util.Map;

import com.google.protobuf.*;
import com.google.protobuf.Descriptors.*;
import com.google.protobuf.DescriptorProtos.*;

public class HelloProto {

	public static void main(String[] args) throws Exception {
		final String descFile = "proto/proto.desc";
		final String proto = "Model.proto";
		final String messageTypeName = "Member";
		
		Map<String, FileDescriptorProto> fileDescProtos = ProtoUtil.getFileDescriptorProtos(descFile);
		
		FileDescriptorProto fileDescProto = fileDescProtos.get(proto);
		FileDescriptor[] dependencies = ProtoUtil.getDependencies(fileDescProtos, fileDescProto);
		FileDescriptor fileDesc = FileDescriptor.buildFrom(fileDescProto, dependencies);
		Descriptor desc = fileDesc.findMessageTypeByName(messageTypeName);
		
		
		displayFieldDetails(desc.findFieldByName("id"));
		displayFieldDetails(desc.findFieldByName("name"));
		displayFieldDetails(desc.findFieldByName("address"));
		displayFieldDetails(desc.findFieldByName("country"));
		displayFieldDetails(desc.findFieldByName("city"));
		displayFieldDetails(desc.findFieldByName("gender"));
		System.out.println();
		
		DynamicMessage dynMessage = DynamicMessage.newBuilder(desc)
				.setField(desc.findFieldByName("id"), 1)
				.setField(desc.findFieldByName("name"), "John Lao")
				.setField(desc.findFieldByName("address"), "Block 1 Happy St.")
				.setField(desc.findFieldByName("country"), createCountryCity(desc.findFieldByName("country").getMessageType()))
				.setField(desc.findFieldByName("city"), createCountryCity(desc.findFieldByName("city").getMessageType()))
				.setField(desc.findFieldByName("gender"), desc.findFieldByName("gender").getEnumType().findValueByName("MALE"))
				.build();
		
		byte[] dynMessageInBytes = dynMessage.toByteArray();
		
		DynamicMessage dynMessage2 = DynamicMessage.parseFrom(desc, dynMessageInBytes);
		
		System.out.println(dynMessage2);
	}
	
	private static DynamicMessage createCountryCity(Descriptor desc) {
		DynamicMessage dynMessage = DynamicMessage.newBuilder(desc)
				.setField(desc.findFieldByName("code"), "SG")
				.setField(desc.findFieldByName("name"), "Singapore")
				.build();
		return dynMessage;
	}
	
	private static void displayFieldDetails(FieldDescriptor fieldDesc) {
		System.out.printf("%s : %s", 
				fieldDesc.getName(), 
				fieldDesc.getJavaType().name());
		if (fieldDesc.getJavaType().name().equals("MESSAGE")) {
			System.out.printf(" (%s)", fieldDesc.getMessageType().getName());
		}
		else if (fieldDesc.getJavaType().name().equals("ENUM")) {
			System.out.printf(" (%s)", fieldDesc.getEnumType().getName());
		}
		System.out.println();
	}
}

Model.proto

package org.hello.proto;

import "Static.proto";

message Member {
	required int32 id = 1;
	required string name = 2;
	required string address = 3;
	required Country country = 4;
	required City city = 5;
	required Gender gender = 6;
}

protoc.bat

@echo off
erase /F /Q proto\proto.desc
protoc.exe --include_imports --proto_path=proto --descriptor_set_out=proto/proto.desc proto/*
@echo on

ProtoUtil.java

package org.hello.protobuf;

import java.io.InputStream;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.google.protobuf.*;
import com.google.protobuf.DescriptorProtos.*;
import com.google.protobuf.Descriptors.*;

public class ProtoUtil {
	
	public static FileDescriptorSet getFileDescriptorSet(String descFilePath) throws Exception {
		InputStream inStream = HelloProto.class.getClassLoader().getResourceAsStream(descFilePath);
		FileDescriptorSet fileDescSet = FileDescriptorSet.parseFrom(inStream);
		return fileDescSet;
	}
	
	public static Map<String, FileDescriptorProto> getFileDescriptorProtos(String descFilePath) throws Exception {
		FileDescriptorSet fileDescSet = getFileDescriptorSet(descFilePath);
		return getFileDescriptorProtos(fileDescSet);
	}
	
	public static Map<String, FileDescriptorProto> getFileDescriptorProtos(FileDescriptorSet fileDescSet) {
		Map<String, FileDescriptorProto> map = new HashMap<String, FileDescriptorProto>();
		List<FileDescriptorProto> fileDescProtos = fileDescSet.getFileList();
		for (FileDescriptorProto fileDescProto : fileDescProtos) {
			map.put(fileDescProto.getName(), fileDescProto);
		}
		return map;
	}
	
	public static FileDescriptor[] getDependencies(Map<String, FileDescriptorProto> fileDescProtos, FileDescriptorProto fileDescProto) throws Exception {
		if (fileDescProto.getDependencyCount() == 0)
			return new FileDescriptor[0];
		
		ProtocolStringList dependencyList = fileDescProto.getDependencyList();
		String[] dependencyArray = dependencyList.toArray(new String[0]);
		int noOfDependencies = dependencyList.size();
		
		FileDescriptor[] dependencies = new FileDescriptor[noOfDependencies];
		
		for (int i = 0; i < noOfDependencies; i++) {
			FileDescriptorProto dependencyFileDescProto =  fileDescProtos.get(dependencyArray[i]);
			FileDescriptor dependencyFileDesc = FileDescriptor.buildFrom(dependencyFileDescProto, getDependencies(fileDescProtos, dependencyFileDescProto));
			dependencies[i] = dependencyFileDesc;
		}
		
		return dependencies;
	}
}

Static.proto

package org.hello.proto;

message Country {
	required string code = 1;
	required string name = 2;
}

message City {
	required string code = 1;
	required string name = 2;
}

enum Gender {
	MALE = 0;
	FEMALE = 1;
}