How to Deserialize a JSON String to a Generic Class in Jackson

How can I deserialize a JSON string to a generic class using Jackson, specifically when I need to specify the type parameter?

// Sample JSON String
String jsonString = "{\"found\": 1, \"hits\": [{\"name\": \"item1\"}]}";

Deserializing a JSON string to a generic class in Jackson requires specifying the type parameter since Java's generics are erased during runtime. We'll utilize Jackson's TypeReference for this purpose.

ObjectMapper mapper = new ObjectMapper();
TypeReference<Data<MyType>> typeRef = new TypeReference<Data<MyType>>() {};
Data<MyType> data = mapper.readValue(jsonString, typeRef);

Causes

• Java's type erasure means generic type information is not available at runtime, making it impossible to directly use a regular class deserialization method for generics.
• When using Data.class, the specific type of T is lost.

Solutions

• Use a custom TypeReference for the generic type when deserializing.
• Define a specific type for T in the TypeReference to maintain type safety.

Mistake: Forgetting to provide the TypeReference when deserializing a generic class.

Solution: Always define a TypeReference for the expected type when deserializing generic classes.

Mistake: Using Data.class without a TypeReference leading to runtime errors or incorrect type information.

Solution: Make sure to create and pass a TypeReference that includes the specific type.