DTO projections via JPQL with Hibernate lazy initialization

DTO projections are very important to doing abstraction over model and data processing. Most common interests are fecthing data with a spesific partition and/or different format other than model. Also DTOs can be very usefull for partial database updates. In JPQL, query results can be transfered into DTOs with new keyword as following:

 

SELECT new org.module.submodule.ExampleDTO(b) FROM Book b

Also you can send parameters via constructor separately. But this approach provide you to control DTO flow and lazy initializations.

 

@Getter
@Setter
public class ExampleDTO {

    private String bookName;
    private Set<BookOwner> bookOwners;

    public ExampleDTO (Boob b) {
    
    	this.bookName = b.getName();
        this.bookOwners = b.getBookOwners();
        
        Hibernate.initialize(b.getBookOwners());
    }
}

In the constructor block, you can manage all initialization, property inclusions, property exclusions and customizations.