Support serialization

[dcapwell]

It would be nice if my client code and my server code can both use this lib. If I try to serialize a Operation, all I get is an empty object.

[fge]

Not sure what you want here. Are you creating your operations from scratch without writing them in JSON? That sounds strange. What is your use case?

[dcapwell]

The main use-case is for testing. I have a set of jersey-test tests that will call the service which takes the json patch. My tests currently use maps to construct the json diff request. It would be nice if the tests could construct the json patch objects.

[fge]

Why not just use the JSON form of JSON patches in this case? You can easily read them from a file into a JsonNode and then into a JSON Patch...

Or do I misunderstand your problem?

[dcapwell]

I could do that. My tests create the diff, hit the endpoint, and then check the response (not in json patch format). The main reason why I would like to use the operations is for type safety.

[fge]

Can you elaborate a little more? It looks to me like you submit a JSON patch to the endpoint to modify a resource and check that the resource has effectively been modified afterwards.

But in this case, it means the resources before and after are JSON, right? If this is the case, why not just use JsonNode's equality?

[dcapwell]

Yes, the expected value and the return value could be JsonNode, but thats only the response; the input is in Json patch format.

public MyClass patch(JsonPatch value) {...}

So what I am looking to do is to create the json patch in the test and send it to the method. This will go through jetty-test so the request will serialize the json patch, then deserialize and call the patch method above. Because it goes through the serialization, I have a few options: pass in a json string (maybe from file), create an object that will serialize to json patch format (currently doing this with maps/lists), or build this with JsonNode.

Doing this by creating the string would work, but its error prone. Could also use JsonNode to do this but its more typing. Maps/Lists work but there is no safety that the attribute that I used is correct.

[fge]

And how do jetty-test {de,}serialize exactly? Does it use Serializable?

[dcapwell]

Ah, ok, sorry if there was some confusion. The serialization I was talking about was jackson serialization to json. Here is a sample that shows what I was talking about:

final ObjectMapper mapper = new ObjectMapper();
    mapper.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);

    final String jsonPatch = "[{\"op\": \"add\", \"path\": \"/foo/bar\", \"value\": \"baz\"}]";

    final JsonPatch patch = mapper.readValue(jsonPatch, JsonPatch.class);

    System.out.printf("Deserialized patch: %s\n", patch);

    final String jsonSer = mapper.writeValueAsString(patch);

    System.out.printf("Serialized Json: %s\n", jsonSer);

and the output:

Deserialized patch: [add: path = "/foo/bar", value = "baz"]
Serialized Json: {}

[fge]

Hmmm... OK, now I understand better.

I do use the reading/deserialization part in my tests, but have never used the writing/serialization part.

This can indeed be viewed as a bug. But as to how to fix it, uh... Well, as I said, I have never used the serialization part. I'll have to do some research on why it does not work... If you have some hints, I'd appreciate!

[fge]

OK, this is definitely a bug. The small test program I have made, based on your test, also shows that serializing individual patch operations fails miserably as well.

To be honest, I have never considered the serialization use case, but I believe I have made a mistake. And as I have never done, or been interested by, serialization (Jackson or otherwise) before, I need to learn fast...

[fge]

OK, making progress. I think I can now serialize all individual patch operations correctly -- I need to write test to confirm.

Now, I need to serialize a whole JsonPatch correctly...