The generated gson type adaptor deserialize json with unknown fields

[wolfjiang]

There is a request that deserialize json put the unknown fields on a specified fields, how I do it ? for example, entity is Contact:

@Gson.TypeAdapters
@Value.Immutable
public Contact {
    Long getId();
    String getName();
    JsonObject getOtherFields();
}

The json string is :

{
    "id": 1,
    "name": "my name",
    "custField1": "cust string field",
   "custField2": 2
}

After gson deserialized, the expected Contact Object is(Json format):

    {
        "id": 1,
       "name": "my nqme",
      "otherFields": {
           "custField1": "cust string field",
           "custField2": 2
      }
    }

I dig into the generated GsonAdaptorsContact.java, found that in method eachAttribute(JsonReader in, ImmutableDepartment.Builder builder) , the unknown fields is skip by in.skipValue();. is there a configable feature than put unknows fields to a specified fields, or give me a unknown fields handler to do it myself?

Sorry for my poor Englisth, any advice is welcome, thanks.

[elucash]

Thank you for raising this! I thought that something like that should be supported, but it seems that it is not implemented for Gson. For Jackson it is supported using @JsonAnyGetter, but not for Gson. I can think of creating a custom adapter to do this, but this would skip any advantages of using auto-generated type adapters. I'm marking this as a feature request.

[wolfjiang]

@elucash thanks for reply so soon :d, I expected the auto-generated type adapter have a parameter, ig. @Gson.TypeAdapters(unknowFiledHander=UnknowFieldhander.class), and UnknowFieldhander implemt a interface with method handleUnkownField(Builder builder, String fieldName, Object fieldValue) , and if annotation with unknowFiledHander then auto-generate code new UnknowFieldhander().handleUnkownField(...) replace orginal code in.skipValue() in eachAttribute method. so we can also using auto generated type adaptor other than custom adaptor.

Sorry, I forgot there is a precondition that Entity must be implement Builder interface in order to use for UnknowFieldhander , ig:

@Gson.TypeAdapters
@Value.Immutable
public Contact {
    Long getId();
    String getName();
    JsonObject getOtherFields();
    public static interface Builder {}
}

[elucash]

@wolfjiang having worked with smth similar, I think it will be somewhat problematic to introduce fine-grained API to consume unknown properties, this would require handling stream, managing state and then try to apply these fields to immutable object's builder. A more tractable solution would be to discover special catch-all attributes for unknown fields and generate code in adapter to populate those. To make things clear it would look like this:

@Value.Immutable interface Obj {
  int knownAttribute();
  String andThisOne();
  @Gson.Other Map<String, Object> allTheRestAttributes();
 // this could be `com.google.gson.JsonObject` or map as shown
}

But if a structure of mapping is completely custom/special, I would suggest to just create custom Gson TypeAdapter to handle it instead of introducing complex binding rules.

[wolfjiang]

@elucash cool! @Gson.Other is a good idea to consume unknown properties, it's enough for me, I expected it . thanks!

[wolfjiang]

Hello @elucash, glade to see that 2.6.0-alpha3 is available , but i didn't found how to handle unknown fields in alpha3, can you give me some idea? Thanks!

[elucash]

This is not implemented yet in 2.6.0-alpha3, will be in the next milestone, currently working on completing issues for the next release, stay tuned )

[elucash]

implemented, will be in next release

[wolfjiang]

@elucash , got it. thank you very much!