Dynamic protobuf builder

gistfile1.scala

object Protobufs {

  def newBuilder() : Builder = {
    return new Builder()
  }

  class Builder {

    private val desBuilder : DescriptorProtos.DescriptorProto.Builder = DescriptorProtos.DescriptorProto.newBuilder()
    private val values = new mutable.HashMap[String, Any]()
    private var i = 1
    private var canBuild = true

    def addField[T](fieldName : String, fieldValue : T, fieldType : FieldDescriptorProto.Type) : Builder = {
     require(canBuild, "Builder is no longer valid!")
     val fieldBuilder = DescriptorProtos.FieldDescriptorProto.newBuilder()
       .setName(fieldName).setNumber(i).setType(fieldType)
     desBuilder.addField(fieldBuilder.build())
     values.put(fieldName, fieldValue)
     i+=1
     return this
    }

    def build(messageName : String) : Message = {
      desBuilder.setName(messageName)
      val dsc = desBuilder.build()
      val fileDescP = DescriptorProtos.FileDescriptorProto.newBuilder().addMessageType(dsc).build()
      val fileDecs = new Array[Descriptors.FileDescriptor](0)
      val dynamicDescriptor = Descriptors.FileDescriptor.buildFrom(fileDescP, fileDecs)
      val msgDescriptor = dynamicDescriptor.findMessageTypeByName(messageName)
      val dmBuilder = DynamicMessage.newBuilder(msgDescriptor)
      values.foreach({ case (key, value) =>
        dmBuilder.setField(msgDescriptor.findFieldByName(key), value)
      })
      canBuild = false
      return dmBuilder.build()
    }
  }

  def main(args : Array[String]) {
    val msg = Protobufs.newBuilder()
      .addField("foo", "bar", DescriptorProtos.FieldDescriptorProto.Type.TYPE_STRING)
      .addField("foo2", "bar", DescriptorProtos.FieldDescriptorProto.Type.TYPE_STRING)
      .addField("foo3", "bar", DescriptorProtos.FieldDescriptorProto.Type.TYPE_STRING).build("TestMessage")
    println(msg)
  }
}