Mapowanie z DTO an encję

@Entity
public class Screening {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "screening_gen")
    @SequenceGenerator(name = "screening_gen", sequenceName = "sc_seq", initialValue = 1001)
    private Long id;
    @NotNull
    @OneToOne
    private Movie movie;
}

public class ScreeningDTO {
    private Long id;
    private Movie movie;
}

List of constraint violations:[
	ConstraintViolationImpl{interpolatedMessage='must not be null', propertyPath=movie, rootBeanClass=class model.Screening, messageTemplate='{javax.validation.constraints.NotNull.message}'}]]
2020-01-13 10:20:22.931 ERROR 28418 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.transaction.TransactionSystemException: Could not commit JPA transaction; nested exception is javax.persistence.RollbackException: Error while committing the transaction] with root cause

{
	"movie": {
		"id": 1,
		"title": "The Shawshank Redemption",
		"category": "drama"
	}
}

@Entity
public class Movie {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @NotNull
    @Size(min = 3)
    private String title;
    @Size(min = 3)
    @NotEmpty
    private String category;
}