How to Create a Gson TypeToken for an ArrayList with a Dynamic Item Type?

Gson TypeToken with Dynamic ArrayList Item Type

In Gson, TypeToken is a utility class that can be used to create type information for unknown types at runtime. It is commonly used to deserialize JSON strings into Java objects.

When working with lists, it is possible to have the ArrayList's item type be defined dynamically at runtime. This can be done using reflection.

Problem:

The following code attempts to create a TypeToken for a list with a dynamic item type:

private <T> Type setModelAndGetCorrespondingList2(Class<T> type) {
    Type typeOfObjectsListNew = new TypeToken<ArrayList<T>>() {}.getType();
    return typeOfObjectsListNew;
}

However, this approach results in a SQLException when converting the JSON string to an object due to a mismatch in type definitions.

Solution:

Starting from Gson 2.8.0, you can use TypeToken#getParameterized(Type rawType, Type... typeArguments) to create the TypeToken for a list with a dynamic item type. The solution is:

Type typeOfObjectsListNew = TypeToken.getParameterized(ArrayList.class, myClass).getType();

This creates a TypeToken for an ArrayList with the specified dynamic item type (myClass). You can then use getType() to retrieve the type information for use in deserialization.

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