implementing Custom Object Mapping in Spring Boot while Using Hibernate and JPA
I'm dealing with Could someone explain Could someone explain I'm working on a Spring Boot application with Hibernate and JPA for ORM, and I'm working with an scenario when trying to map my custom DTO to an entity... I have a `UserDTO` that I'd like to map to a `User` entity, but when I attempt to do this, I get the following behavior: ``` org.hibernate.MappingException: No identifier specified for entity: com.example.User ``` I have the following classes: ```java @Entity public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String username; private String email; // getters and setters } ``` ```java public class UserDTO { private String username; private String email; // getters and setters } ``` In my service layer, I am trying to convert the `UserDTO` to a `User` entity: ```java public User convertToEntity(UserDTO userDTO) { User user = new User(); user.setUsername(userDTO.getUsername()); user.setEmail(userDTO.getEmail()); return user; } ``` I thought this would work, but when I save the `User` entity using my repository: ```java userRepository.save(user); ``` I get the aforementioned `MappingException`. I checked that my database table is set up correctly and has an `id` column. I've also made sure that I have the correct database connection configurations. I tried adding the `@Table` annotation to the `User` entity as well, but the behavior continues. I'm using Spring Boot 2.5.0, Hibernate 5.4.32.Final, and JPA 2.2. Is there something I might be missing in my entity mapping or in the configuration? Any help would be greatly appreciated! Could someone point me to the right documentation? Any ideas how to fix this? This issue appeared after updating to Java 3.9. Am I approaching this the right way? My team is using Java for this application. Any suggestions would be helpful.