I want to deserialize json objects to specific types of objects (using Gson library) based on type
field value, eg.:
[
{
"type": "type1",
"id": "131481204101",
"url": "http://something.com",
"name": "BLAH BLAH",
"icon": "SOME_STRING",
"price": "FREE",
"backgroundUrl": "SOME_STRING"
},
{
....
}
]
So type
field will have different (but known) values. Based on that value I need to deserialize that json object to appropriate model object, eg.: Type1Model, Type2Model etc.
I know I can easily do that before deserialization by converting it to JSONArray
, iterate through it and resolve which type it should be deserialized to. But I think it's ugly approach and I'm looking for better way. Any suggestions?
You may implement a JsonDeserializer
and use it while parsing your Json value to a Java instance. I'll try to show it with a code which is going to give you the idea:
1) Define your custom JsonDeserializer
class which creates different instance of classes by incoming json value's id property:
class MyTypeModelDeserializer implements JsonDeserializer<MyBaseTypeModel> {
@Override
public MyBaseTypeModel deserialize(final JsonElement json, final Type typeOfT, final JsonDeserializationContext context)
throws JsonParseException {
JsonObject jsonObject = json.getAsJsonObject();
JsonElement jsonType = jsonObject.get("type");
String type = jsonType.getAsString();
MyBaseTypeModel typeModel = null;
if("type1".equals(type)) {
typeModel = new Type1Model();
} else if("type2".equals(type)) {
typeModel = new Type2Model();
}
// TODO : set properties of type model
return typeModel;
}
}
2) Define a base class for your different instance of java objects:
class MyBaseTypeModel {
private String type;
// TODO : add other shared fields here
}
3) Define your different instance of java objects' classes which extend your base class:
class Type1Model extends MyBaseTypeModel {
// TODO: add specific fields for this class
}
class Type2Model extends MyBaseTypeModel {
// TODO: add specific fields for this class
}
4) Use these classes while parsing your json value to a bean:
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.registerTypeAdapter(MyBaseTypeModel.class, new MyTypeModelDeserializer());
Gson gson = gsonBuilder.create();
MyBaseTypeModel myTypeModel = gson.fromJson(myJsonString, MyBaseTypeModel.class);
I can not test it right now but I hope you get the idea. Also this link would be very helpful.