使用谓词查询 dsl 并获取连接

Question

是否有机会使用谓词获取连接实体？

    @Entity
public class Student {

    @Id
    private int id;

    private String hobby;

    private String favouriteColor;

    private String name;

    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.REFRESH)
    @JoinColumn(name = "CLASS_ID", referencedColumnName = "ID")
    private Classroom classroom;
}

@Entity
public class Classroom {

    @Id
    private int id;

    private String classRoom;

    private List<Student> students;

}

我有一些谓词

public class StudentPredicate {

    private StudentPredicate() {}

    public static Predicate createPredicate(final Student filter) {
        QStudent student = QStudent.student;

        BooleanBuilder builder = new BooleanBuilder();

        if (isNotBlank(filter.getHobby())) {
            builder.and(student.hobby.eq(filter.getHobby());
        }
        if (isNotBlank(filter.getFavouriteColor())) {
            builder.and(student.favouriteColor.eq(filter.getFavouriteColor()));
        }


        return builder.getValue();
    }

}

和存储库

@Repository
public interface StudentRepository extends CrudRepository<Student, Integer>, QueryDslPredicateExecutor<Student> {

}

现在我怎样才能找到所有已获取教室的学生？

studentRepository.findAll(predicate)

查询dsl这些findAll应该取教室怎么说？

Answer 1

由于 Student 类中的教室字段有 FetchType.LAZY，所以当您调用 getClassRoom() 时，实际上会从 db 中获取相关实体，或者您可以使用FetchType.EAGER。