如何使用本机查询在JPA中执行嵌套连接
我有现有的桌位学生、临时演员和这个结构的地址。
Table student
------------------------------------------
id | name
------------------------------------------
1 | John
------------------------------------------
Table extras
-----------------------------------------------------------------
id | student_id | extras_key | extras_value
-----------------------------------------------------------------
1 | 1 | class | X3
2 | 1 | address_id | addr-2
-----------------------------------------------------------------
Table address
--------------------------------------------
addr_id | name | city
--------------------------------------------
addr-2 | Office | San Jose
--------------------------------------------如何在上连接这些表？我目前的代码是
学生实体班
@Entity
@Table(name = "student")
@Data
public class Student implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id", nullable = false)
private Integer id;
@Column(name = "name", nullable = false, columnDefinition = "TEXT")
private String name;
// @OneToOne
// @JoinColumn(name = "id", referencedColumnName = "student_id")
// private Extras extras;
@OneToMany(mappedBy = "studentId")
private Set<Extras> extras;
}额外实体类：
@Data
@Entity
@Table(name="extras")
public class Extras implements Serializable {
@Id
@Column(name="id")
private int id;
@Column(name="student_id", nullable = false)
private int studentId;
@Column(name="extras_key", nullable = false)
private String extrasKey;
@Column(name="extras_value", nullable = false)
private String extrasValue;
@OneToOne(optional = false)
@NotFound(action = NotFoundAction.IGNORE)
@JoinColumn(name = "extras_value", referencedColumnName = "addr_id", insertable = false, updatable = false)
private Address address;
}和地址实体类
@Entity
@Table(name="address")
@Data
public class Address implements Serializable {
@Id
@Column(name="addr_id")
private String addrId;
@Column(name="name")
private String name;
@Column(name="city")
private String city;
}这是我的存储库类
@Repository
public interface StudentRepository extends CrudRepository<Student, Integer> {
@Query(value = "select * from student " +
"JOIN extras ON student.id=extras.student_id " +
"JOIN address ON address.addr_id = extras.extras_value", nativeQuery = true)
List<Student> findAllData();
}但是，当我在“学生”实体中使用OneToMany时，我发现异常OneToMany无法延迟初始化角色集合: com.jpa.belajarjpa.enitities.Student.extras，无法初始化代理-没有会话“”。但是当我在“学生”实体中使用OneToOne时，我没有遇到异常，而是得到了错误的结果，“学生”(id=1，name=john，extras=null)，当我执行这个查询时，它会显示正确的结果 SELECT *来自address.addr_id = extras.extras_value上student.id=extras.student_id连接地址的student.id=extras.student_id连接附加地址。
回答 2
Stack Overflow用户
发布于 2020-11-12 08:14:24
您需要在HQL查询中使用join获取，如下所示：
@Repository
public interface StudentRepository extends CrudRepository<Student, Integer> {
@Query("FROM Student s " +
"JOIN FETCH s.extras e " +
"JOIN FETCH e.address")
List<Student> findAllData();
}spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true是一种反模式.如果我是你我就不会用了。
Stack Overflow用户
发布于 2020-11-12 04:31:34
通过在属性中添加spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true来解决
https://stackoverflow.com/questions/64784914
复制相似问题
腾讯云开发者
Copyright © 2013 - 2026 Tencent Cloud. All Rights Reserved. 腾讯云 版权所有
深圳市腾讯计算机系统有限公司 ICP备案/许可证号：粤B2-20090059 
粤公网安备44030502008569号
腾讯云计算（北京）有限责任公司 京ICP证150476号 | 京ICP备11018762号