Gson parse to POJO with custom key

问题

I have json data like this:

meds:
[
  {
     MedsID: 8063,
     updated_at: "2015-11-04T06:59:55",
     treatment_date: "2015-11-04T00:00:00",
     name: "name"
  }
],
scores: 
[
 {
   ScoreID: 75820,
   updated_at: "2015-11-04T06:59:55"
   dialysis_flow: 233,
 }
],
 dias: 
[
 {
   DiasID: 75820,
   updated_at: "2015-11-04T06:59:55"
   name: "K",
 }
]

And here is my Entities:

  public class BaseData{
      public long id;
  }

  public class Med extends BaseData{
      public String name;
      public String updated_at;
      public String treatment_date;
  }

  public class Score extends BaseData{
      public String updated_at;
      public int dialysis_flow;
  }

  public class Dias extends BaseData{
      public String name;
      public String updated_at;
      public String treatment_date;
  }

Because all entities are mapped from database with the id key (as I use orm db, it's loaded by property name ). So I need to parse all other keys MedsID, DiasID, ScoreID into id when mapping by gson.
Is there any way to achieve that?

Update:
I use registerTypeHierarchyAdapter instead of registerTypeAdapter and it can work. But this way is extremely slow as my json data is very large.

public class DataDeserializer implements JsonDeserializer<BaseData>      {
@Override
public BaseData deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
    JsonObject ja = json.getAsJsonObject();
    Gson gson = new Gson();
    final String[] mapIds = {"ScoreID", "MedsID", "DiasID"};
    BaseData data = gson.fromJson(ja, typeOfT);

    for (String idKey:mapIds){
        if(ja.has(idKey)){
            data.id = ja.get(idKey).getAsLong();
            break;
        }
    }

    return data;
    } 
}

 Gson gson = new GsonBuilder().registerTypeHierarchyAdapter( BaseData.class, new DataDeserializer() ).create();

Does anyone know other way to achieve that?

回答1:

The only way to achieve this is writing a custom de-serializer. Please see below example:

public class CustomDeserializer implements JsonDeserializer<Dias>{

    public Dias deserialize( JsonElement json, Type typeOfT, JsonDeserializationContext context ) throws JsonParseException{
        JsonObject ja = json.getAsJsonObject();

        Dias dias = new Gson().fromJson( ja, Dias.class );
        dias.id = ja.get( "DiasID" ).getAsLong();

        return dias;
    }

}

Register it;

 String dias = "{'DiasID':75820,'updated_at':'2015-11-04T06:59:55','name':'K'}";
 Gson gson = new GsonBuilder().registerTypeAdapter( Dias.class, new CustomDeserializer() ).create();
 Dias dias2 = gson.fromJson( dias, Dias.class );

 System.out.println( dias2.id );

Output:

75820

This is just an example, you can extend it by writing a deserializer for your own base class.

来源：https://stackoverflow.com/questions/33760396/gson-parse-to-pojo-with-custom-key