Deserializing ImmutableList using Gson

Question

I\'m using quite a few immutable collections and I\'m curious how to deserialize them using Gson. As nobody answered and I\'ve found the solution myself, I\'m simplifying th

Answer 1

Update: There's https://github.com/acebaggins/gson-serializers which covers many guava collections:

• ImmutableList
• ImmutableSet
• ImmutableSortedSet
• ImmutableMap
• ImmutableSortedMap

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How to write a single Deserializer working for all ImmutableList?

The idea is simple, transform the passed Type representing an ImmutableList into a Type representing List, use the build-in Gson's capability to create a List and convert it to an ImmutableList.

class MyJsonDeserializer implements JsonDeserializer> {
    @Override
    public ImmutableList deserialize(JsonElement json, Type type, JsonDeserializationContext context) throws JsonParseException {
        final Type type2 = ParameterizedTypeImpl.make(List.class, ((ParameterizedType) type).getActualTypeArguments(), null);
        final List list = context.deserialize(json, type2);
        return ImmutableList.copyOf(list);
    }
}

There are multiple ParameterizedTypeImpl classes in Java libraries I use, but none of them intended for public usage. I tested it with sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl.

How to register it for all ImmutableList?

That part is trivial, the first argument to register is java.lang.reflect.Type which mislead me to using ParameterizedType, where simply using Class does the job:

final Gson gson = new GsonBuilder()
    .registerTypeAdapter(ImmutableList.class, myJsonDeserializer)
    .create();