How to Deserialize Generic Collections in Gson Using TypeToken?

Deserializing Generic Collections with Gson

You're looking to deserialize a list object using Google Gson, but you're encountering challenges due to generic types.

Alternative Approach

The error you're facing suggests that new List() {} does not implement the inherited abstract methods. Instead, you can use TypeToken to specify the generic type at runtime:

Type listType = new TypeToken<List<MyClass>>() {}.getType();
MyClass mc = new Gson().fromJson(result, listType);

Exception Handling

The NullPointerException you're encountering suggests that the list type is not properly formatted. Check the following:

• Ensure that result is not null.
• Debug the listType to verify that the parameterized type is set correctly.

TypeToken Explanation

The TypeToken class allows you to capture generic types at compile time and represent them as runtime types. Its anonymous subclass encapsulates the specific type information, enabling Gson to deserialize the corresponding object correctly.

Reference for Future Developers

• https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/TypeToken.html
• https://stackoverflow.com/questions/12112101/gson-and-multiple-type-parameters-in-generic-class

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