Java Type Generic as Argument for GSON

java generics gson
Rodrigo Asensio picture Rodrigo Asensio · Jan 3, 2013 · Viewed 41.3k times · Source

In GSON to get a list of objects you do

Gson gson = new Gson();
Type token = new TypeToken<List<MyType>>(){}.getType();
return gson.fromJson(json, token);

It works great, but I want to go further and have MyType parametrized so I can have a common function to parse list of objects with this code

// the common function 
public <T> List<T> fromJSonList(String json, Class<T> type) {
  Gson gson = new Gson();
  Type collectionType = new TypeToken<List<T>>(){}.getType();
  return gson.fromJson(json, collectionType);
}

// the call
List<MyType> myTypes = parser.fromJSonList(jsonString, MyType.class);

Sadly returns an array of StringMaps, not the type. T is being interpreted as another generic type, not my type. Any workaround ?

Answer

oldergod picture oldergod · Jun 1, 2017

Since gson 2.8.0, you can use TypeToken#getParametized((Type rawType, Type... typeArguments)) to create the typeToken, then getType() should do the trick.

For example:

TypeToken.getParameterized(List.class, myType).getType();

Related questions

Google Gson - deserialize list<class> object? (generic type)

I want to transfer a list object via Google Gson, but I don't know how to deserialize generic types. What I tried after looking at this (BalusC's answer): MyClass mc = new Gson().fromJson(result, new List<MyClass>(){}.getClass()); …

Read More
Multiple converters with Retrofit 2

I have a HATEOAS (HAL) REST service and managed to talk to it with the code below (using halarious as a conversion engine) but when I try to merge the converters (stallone and stallone2), the app will always pick up …

Read More
How to create a generic array in Java?

Due to the implementation of Java generics, you can't have code like this: public class GenSet<E> { private E a[]; public GenSet() { a = new E[INITIAL_ARRAY_LENGTH]; // error: generic array creation } } How can I implement this while …

Read More