generate_descriptor.scala

import com.google.protobuf.DescriptorProtos.FileDescriptorSet
import java.io.FileInputStream
import scala.collection.JavaConverters._

val descriptorFile = new FileInputStream("path/to/descriptorfile/descriptorfilename.desc")
val descriptorSetObject = FileDescriptorSet.parseFrom(descriptorFile)

//DescriptorSet contains multiple file descriptors including the dependencies
//To get a particular file descriptor, just filter out using the file's name

val abcProtoFileDescriptor = FileDescriptor.buildFrom(descriptorSetObject.getFileList.asScala.filter(_.getName.contains("abc")).head, Array())

//Once you have the file descriptor, you can extract message descriptors from it using message names
//e.g. suppose the message name is TestProtoMessage
val messageDescriptor = abcProtoFileDescriptor.getMessageTypes.iterator().asScala.filter(_.getName=="TestProtoMessage").toList.head

//To Parse a byte-array to proto object using dynamic messages
val protoObject = DynamicMessage.parseFrom(messageDescriptor, inputByteArray)