C# protobuf-net serialized object to java

Question

So I have a small problem:

A message is sent using MQTT, it consists of a series of serialized objects using protobuf-net in C# (I can't modify this code, but I have access to the source). At the other end i receive the serialized objects in Java, the problem is I can't seem to be able to deserialize the objects using protobuf, if anyone ever had this problem and solved it, please help :)

Example of object from C#:

using ProtoBuf;

namespace Concentrator.Services
{
[ProtoContract]
public class MeterID
{
    private byte[] _id;

    [ProtoMember(1)]
    public byte[] ID
    {
        get { return _id; }
        set { _id = value.Length == 16 ? value : null; }
    }

    [ProtoMember(2)] public string MeterType;
}
}

My attempt at recreating the same object in Java (the .proto file):

syntax = "proto2";

 package mqtt.entity;

 option java_package = "mqtt.entity";
 option java_outer_classname = "ProtoMeter";
 message Meter {
    optional bytes ID = 1;
     optional string MeterType = 2;
  }

  message MeterID {
     repeated Meter mid = 1;
 }

A solution to this example would be a huge help, Thanks a lot.

The code where the object is deserialized in C#:

var ms = new MemoryStream(data, 7, data.Length - 9)
var res = Serializer.Deserialize<List<MeterID>>(ms);

this works in C#, I'm trying to achieve the same thing in java

You say "I can't seem to be able to deserialize the objects", but what happens when you try? Compilation errors? Runtime errors? Data corruption? — Joachim Isaksson, Apr 08 '13 at 12:49

Marc Gravell · Accepted Answer · 2013-04-08T13:31:14.403

3

The message in your C# code matches just:

message MeterID {
    optional bytes ID = 1;
    optional string MeterType = 2;
}

There is no need for a 2-level model (unless you're using *WithLengthPrefix in the C# code). You can also get that output by using:

var proto = Serializer.GetProto<MeterID>();

With your edit, a List<MeterID> could be mapped as

message List_MeterID {
    repeated MeterID items = 1;
}

to be used in combination with the previous MeterID fragment. Which is what you have in the question. So it comes down to "what currently happens?".

edited Apr 08 '13 at 13:31

answered Apr 08 '13 at 12:50

Marc Gravell

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I'm trying to deserialize in java, the objects comes in a list, I'll update the first post to add the code where they are deserialized in C# – cosmin.danisor Apr 08 '13 at 13:09
@cdanisor you didn't mention the `List` :p With that, the .proto from your original question is fine. So that then prompts the question - what happens now? what doesn't work? do you get an exception...? or...? – Marc Gravell Apr 08 '13 at 13:32
There is another problem now :) Exception in thread "MQTT Client Callback" java.lang.VerifyError: class mqtt.entity.ProtoMeter$MeterID overrides final method getUnknownFields.()Lcom/google/protobuf/UnknownFieldSet; at java.lang.ClassLoader.defineClass1(Native Method) The class generated by protoc seems to be bugged, it overrides a final method. – cosmin.danisor Apr 08 '13 at 13:37
2

@cdanisor first check you have the current build of the google protobuf (not protobuf-net) package; if `protoc` still emits illegal java, then I would suggest to report it on the [protobuf list](https://groups.google.com/forum/?fromgroups#!forum/protobuf) or on the protobuf (not protobuf-net) [issue tracker](https://code.google.com/p/protobuf/issues/list) – Marc Gravell Apr 08 '13 at 13:42
You were right, I used a wrong version of protoc, different from the jar, it works flawlessly now. Thanks a lot. – cosmin.danisor Apr 08 '13 at 13:59
Hi Cosmin, i am trying to achieve the same thing, trying to de-serialize the .bin file created in C# to object in JAVA.How have you achieved ? – Aada Aug 05 '13 at 11:58
@Aada it should *just work*. What problems have you encountered? – Marc Gravell Aug 05 '13 at 12:03

score 1 · Answer 2 · answered Apr 08 '13 at 12:50

1

try regenerate proto-file by GetProto<T>

answered Apr 08 '13 at 12:50

burning_LEGION

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Be more specific please I never used protobuf before – cosmin.danisor Apr 08 '13 at 13:11
1

`var res = Serializer.GetProto>;` and use `res` – burning_LEGION Apr 08 '13 at 13:15
Ok getting that in C# it's a good step but how do I export it in java? – cosmin.danisor Apr 08 '13 at 13:21
http://stackoverflow.com/questions/7947277/protocol-buffer-how-to-import https://developers.google.com/protocol-buffers/docs/proto – burning_LEGION Apr 08 '13 at 13:23
GetProto method is great, because this was the simplest example other objects are way bigger and this makes my life a lot easier – cosmin.danisor Apr 08 '13 at 13:38
1

@cdanisor the re-implementation of `GetProto` is relatively recent compared to most of the code - I think it handles most scenarios, but if you get any problems with it, let me know – Marc Gravell Apr 08 '13 at 13:40

C# protobuf-net serialized object to java

2 Answers2