Could you explain the role of Mapper in data transformation for DTO classes?

In the context of data transformation for DTO (Data Transfer Object) classes, a Mapper is responsible for converting between application layers — usually between database entities and DTOs used for data transfer, for example, in APIs.

The role of the Mapper includes:

• Isolating business logic from data presentation details.
• Simplifying and standardizing the data transformation process.
• Ensuring security by excluding the transfer of unnecessary or sensitive fields.

An example of a simple Mapper in Java:

public class UserMapper {
    public static UserDTO toDTO(UserEntity entity) {
        UserDTO dto = new UserDTO();
        dto.setId(entity.getId());
        dto.setName(entity.getName());
        // other fields
        return dto;
    }

    public static UserEntity toEntity(UserDTO dto) {
        UserEntity entity = new UserEntity();
        entity.setId(dto.getId());
        entity.setName(dto.getName());
        // other fields
        return entity;
    }
}

Thus, the Mapper simplifies support and development of the code, separating data transformation from business logic.