best practices for ClassCastException When Using Spring Data JPA with Projections in Java 17?
I'm trying to debug I'm deploying to production and I've searched everywhere and can't find a clear answer..... I've looked through the documentation and I'm still confused about I'm working with a `ClassCastException` while trying to use projections with Spring Data JPA in my Java 17 application... Specifically, I'm trying to retrieve a list of custom DTOs from my repository, but I'm getting an behavior when casting the result. Here's the relevant part of my code: ```java // DTO class public class UserDTO { private String username; private String email; public UserDTO(String username, String email) { this.username = username; this.email = email; } // Getters and Setters } // Repository interface public interface UserRepository extends JpaRepository<User, Long> { @Query("SELECT new com.example.UserDTO(u.username, u.email) FROM User u") List<UserDTO> findAllUserDTOs(); } ``` When I call this method from my service, I receive the following exception: ``` java.lang.ClassCastException: class com.example.User want to be cast to class com.example.UserDTO ``` I have verified that my `User` entity and `UserDTO` class are correctly defined. I also made sure to use the correct package name in the JPQL query. However, I'm still getting this behavior. I've tried cleaning and rebuilding the project, and I've ensured that my dependencies are up to date, including Spring Boot version 2.5.4. Is there something I am missing in my setup, or is there a best practice for using projections with Spring Data JPA that I should be aware of? Any help would be greatly appreciated! My development environment is Windows. What's the best practice here? This is part of a larger API I'm building. What am I doing wrong? I'm open to any suggestions. For reference, this is a production service. Am I approaching this the right way?