Java Spring数据JPA-规范查询

有一个使用属性表达式的查询：：

我做错了什么或忘记添加了什么

查询：按教师姓名显示所有学生

基本实体：

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
abstract class BaseModel {

@Id
@Column(name = "id")
@Getter
@GeneratedValue(strategy = GenerationType.AUTO)
private long id;

protected BaseModel() {
  }
}

实体教师：

@Entity
@Table(name = "teacher")
public final class Teacher extends BaseModel {

@OneToOne
@JoinColumn(name = "teacher_id")
private PupilInClassRoom pupilInClassRoom;

@Column(nullable = false)
@Getter
@Setter
private String name;

@Column(nullable = false)
@Getter
@Setter
private String surname;

@Column(nullable = false)
@Getter
@Setter
private String discipline;

public Teacher() {
  }
}

实体学生：

@Entity
@Table(name = "pupil")
public final class Pupil extends BaseModel {

@OneToOne
@JoinColumn(name = "pupil_id")
private PupilInClassRoom pupilInClassRoom;

@Column(nullable = false)
@Getter
@Setter
private String name;

@Getter
@Setter
@Column(nullable = false)
private String surname;

public Pupil() {

  }
}

实体教室：

@Entity
@Table(name = "class_room")
public final class ClassRoom extends BaseModel {

@OneToOne
@JoinColumn(name = "class_Room_id")
private PupilInClassRoom pupilInClassRoom;

@Column(nullable = false)
@Getter
@Setter
private String name;

public ClassRoom() {
   }
}

@Entity
@Table(name = "pupil_in_class_room")
public final class PupilInClassRoom  extends BaseModel {

@OneToOne(mappedBy = "pupilInClassRoom")
@Getter
@Setter
private Pupil pupil;

@OneToOne(mappedBy = "pupilInClassRoom")
@Getter
@Setter
private ClassRoom classRoom;

@OneToOne(mappedBy = "pupilInClassRoom")
@Getter
@Setter
private Teacher teacher;

public PupilInClassRoom() {

}

实体教室：

@Entity
@Table(name = "class_room")
public final class ClassRoom extends BaseModel {

@OneToOne
@JoinColumn(name = "class_Room_id")
private PupilInClassRoom pupilInClassRoom;

@Column(nullable = false)
@Getter
@Setter
private String name;

public ClassRoom() {
   }
}

@Entity
@Table(name = "pupil_in_class_room")
public final class PupilInClassRoom  extends BaseModel {

@OneToOne(mappedBy = "pupilInClassRoom")
@Getter
@Setter
private Pupil pupil;

@OneToOne(mappedBy = "pupilInClassRoom")
@Getter
@Setter
private ClassRoom classRoom;

@OneToOne(mappedBy = "pupilInClassRoom")
@Getter
@Setter
private Teacher teacher;

public PupilInClassRoom() {

}

Join瞳孔\u瞳孔classroomjoin=
root.join（“pupilin教室”）；
加入教师\学生班级加入=
学生们在教室里加入。加入（“老师”）；

root.join（“学生id”）

->

root.join（“学生id”）

加入

->

加入

pupliClassRoomJoin.join（“教师id”）

->

pupliClassRoomJoin.join（“教师”）

---

上面的更新是我猜做你想做的事情所需要的。可以尝试吗？

问题的解决方案：

public final class PupilSpecification {
        public static Specification<Pupil> findPupilByTeacherSpecification(String name) {
            return new Specification<Pupil>() {
                @Override
                public Predicate toPredicate(Root<Pupil> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                    root = criteriaQuery.from(Pupil.class);
                    Join<Pupil, PupilInClassRoom> pupil_PupilInClassRoomJoin = root.join("pupilInClassRoom");
                    Join<PupilInClassRoom, Teacher> teacher_PupilInClassRoomJoin = pupil_PupilInClassRoomJoin.join("teacher");
                    return criteriaBuilder.equal(teacher_PupilInClassRoomJoin.get(Teacher_.Name),name);
                }
            };
        }
    }

---

是的，你的回答解决了我的问题）谢谢。你做得怎么样。加入（课堂）和。加入（老师）？我添加了元模型）

Join<Pupil, PupilInClassRoom>   pupil_PupilInClassRoomJoin   =
        root.join("pupilInClassRoom");
Join<PupilInClassRoom, Teacher> teacher_PupilInClassRoomJoin = 
        pupil_PupilInClassRoomJoin.join("teacher");

public final class PupilSpecification {
        public static Specification<Pupil> findPupilByTeacherSpecification(String name) {
            return new Specification<Pupil>() {
                @Override
                public Predicate toPredicate(Root<Pupil> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                    root = criteriaQuery.from(Pupil.class);
                    Join<Pupil, PupilInClassRoom> pupil_PupilInClassRoomJoin = root.join("pupilInClassRoom");
                    Join<PupilInClassRoom, Teacher> teacher_PupilInClassRoomJoin = pupil_PupilInClassRoomJoin.join("teacher");
                    return criteriaBuilder.equal(teacher_PupilInClassRoomJoin.get(Teacher_.Name),name);
                }
            };
        }
    }

@Generated(value = "org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor")
@StaticMetamodel(Teacher.class)
public abstract class Teacher_ {
    public static volatile SingularAttribute<Teacher,String> name;
    public static volatile SingularAttribute<Teacher,String> surmane;
    public static volatile SingularAttribute<Teacher,String> discipline;
    public static volatile SingularAttribute<BaseModel,Integer> id;

    public static final String Name = "name";
    public static final String Surname = "surname";
    public static final String Discipline = "discipline";
    public static final String Id = "id";
}

pupilRepository.findAll(PupilSpecification.findPupilByTeacherSpecification("Alla"))