JaxRs.java

package stackoverflow.generics;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;

import javax.ws.rs.core.GenericEntity;
import javax.ws.rs.core.Response;

public class JaxRs {

	public static void main(String[] args) {
		
		System.out.println(new UserResource().findAll());
	}
	
	static class UserModel {
		String name;
		UserModel(String name) {
			this.name = name;
		}
	}

	static class UserResource extends Resource<UserModel> {

		@Override
		public List<UserModel> getAll() {
			List<UserModel> ret = new ArrayList<UserModel>();
			ret.add(new UserModel("Foo"));
			ret.add(new UserModel("Bar"));
			ret.add(new UserModel("Baz"));

			return ret;
		}
	
	}	
	
	static abstract class Resource<T> {
		
		public Type getType() {
			Type type = ((ParameterizedType) getClass().getGenericSuperclass())
					.getActualTypeArguments()[0];
			return new ListOfSomething(type);
		}
		
		public Response findAll() {
			List<T> data = getAll();
			return Response.ok(new GenericEntity<List<T>>(data, getType())).build();
		}
		
		public abstract List<T> getAll();
	}

	static class ListOfSomething implements ParameterizedType {

		ListOfSomething(Type type) {
			this.type = type;
		}
		
		Type type;
		
		@Override
		public Type[] getActualTypeArguments() {
			return new Type[] { type };
		}

		@Override
		public Type getRawType() {
			return List.class;
		}

		@Override
		public Type getOwnerType() {
			return JaxRs.class;
		}
	}
}