GSON generics serialization

Question

Possible Duplicate:
deserializing generics with gson

So I need to do:

Type fluentType = new TypeToken<BruteForceFluentImpl<GtlDigestor.Data>>() {}.getType();

instead of

Type fluentType = new TypeToken<Fluent<T>>() {}.getType(); // <-- i want to be able to do something like this.

String json = gson.toJson(fluent, fluentType);

This means that every time I have to specify a different type parameter for the Fluent class, I need to change my code in order to specify it. Right now, the type parameter is GtlDigestor.Data.

How do I do this? (the second line of code won't work)

Answer 1

You need to tell Gson the actual parameterized type (e.g. BruteForceFluentImpl<GtlDigestor.Data>, including the actual runtime raw type and the actual type parameter value) at runtime, because Gson needs to save this information.

Using TypeToken is the easiest way to get a Type, but to use it you must hard-code the exact type in the source (no type parameters like T). If you would like to put the code in a method that will be re-used with different types, then perhaps this method should accept the Type as a parameter, which the caller needs to pass in. The type can then be hard-coded at the caller's location, each of which presumably only uses a fixed type.

Or, if you need to generate the Type completely dynamically at runtime based on the raw type and type parameters, see my answer for the question here.