Java 17: implementing Serialization of Generic Collections in JAX-RS Responses
I'm updating my dependencies and I'm working on a personal project and I'm having trouble serializing a generic collection when returning responses in my JAX-RS application. I'm using Java 17 with Jackson for JSON serialization, and I have a resource method designed to return a list of a custom generic type. However, when I try to return a `List<MyGenericType<String>>`, I receive the following behavior: `com.fasterxml.jackson.databind.JsonMappingException: want to construct instance of 'MyGenericType' (no Creators, like default constructor, exist)`. Here’s the code for my resource class: ```java @Path("items") public class ItemResource { @GET @Produces(MediaType.APPLICATION_JSON) public List<MyGenericType<String>> getItems() { List<MyGenericType<String>> items = new ArrayList<>(); items.add(new MyGenericType<>("Item1")); items.add(new MyGenericType<>("Item2")); return items; } } ``` And the `MyGenericType` class looks like this: ```java public class MyGenericType<T> { private T value; public MyGenericType(T value) { this.value = value; } // Getters and setters public T getValue() { return value; } } ``` I’ve tried adding a default constructor to `MyGenericType`, but the behavior continues. Additionally, I've confirmed that Jackson is configured in my `web.xml` for JAX-RS. Here’s the relevant part: ```xml <servlet> <servlet-name>Jersey REST Service</servlet-name> <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class> <init-param> <param-name>jersey.config.server.provider.packages</param-name> <param-value>com.example.resources</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> ``` I’ve also ensured that the Jackson dependency is included in my `pom.xml`: ```xml <dependency> <groupId>com.fasterxml.jackson.jaxrs</groupId> <artifactId>jackson-jaxrs-json-provider</artifactId> <version>2.12.5</version> </dependency> ``` What could be causing this serialization scenario with my generic type? Any insights or suggestions would be greatly appreciated! I'm working on a service that needs to handle this. Any ideas what could be causing this? This is part of a larger desktop app I'm building.