JPA 和 Hibernate 在第一次尝试使用 JSON 时不会更新一对多关系答案

【问题标题】：JPA and Hibernate dosnt update one to many relation in first try in spring rest with JSONJPA 和 Hibernate 在第一次尝试使用 JSON 时不会更新一对多关系
【发布时间】：2018-03-26 22:54:06
【问题描述】：

我已经尝试过使用休眠、JPA 和 JSON 进行 spring rest。我必须像下面这样的实体：

大学.java

@Entity()
@Table(name = "university")
public class University extends BaseEntity {
    private String uniName;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval = true)
    @JoinColumn(name = "university_id", foreignKey = @ForeignKey(name = "university_id"))
    private Collection<Student> students;

    //setters and getters
}

学生.java

@Entity
@Table(name = "student")
public class Student extends BaseEntity {
    private String stuName;

    @ManyToOne(fetch = FetchType.EAGER)
    @JsonIgnoreProperties("students")
    private University university;

    //setters and getters
}

我的数据库中有这个虚拟值。

[
  {
    "id": 1,
    "uniName": "uni1",
    "students": [
      {
        "id": 1,
        "stutName": "st1",
        "university": {
          "id": 1,
          "uniName": "uni1"
        }
      },
      {
        "id": 2,
        "stutName": "st2",
        "university": {
          "id": 1,
          "uniName": "uni1"
        }
      }
    ]
  }
]

第一次尝试：当我尝试用学生更新大学时，没有成功这是我的休眠日志

Hibernate:
    select
        university0_.id as id1_5_1_,
        university0_.uniName as uniName2_5_1_,
        students1_.university_id as universi3_4_3_,
        students1_.id as id1_4_3_,
        students1_.id as id1_4_0_,
        students1_.stuName as stuName2_4_0_,
        students1_.university_id as universi3_4_0_
    from
        university university0_
    left outer join
        student students1_
            on university0_.id=students1_.university_id
    where
        university0_.id=?
Hibernate:
    update
        student
    set
        stuName=?,
        university_id=?
    where
        id=?
Hibernate:
    update
        university
    set
        uniName=?
    where
        id=?
Hibernate:
    update
        student
    set
        stuName=?,
        university_id=?
    where
        id=?

第二次尝试：但是当我第二次发布相同的数据时它是成功的并且休眠日志是

Hibernate:
    select
        university0_.id as id1_5_1_,
        university0_.uniName as uniName2_5_1_,
        students1_.university_id as universi3_4_3_,
        students1_.id as id1_4_3_,
        students1_.id as id1_4_0_,
        students1_.stuName as stuName2_4_0_,
        students1_.university_id as universi3_4_0_
    from
        university university0_
    left outer join
        student students1_
            on university0_.id=students1_.university_id
    where
        university0_.id=?
Hibernate:
    select
        student0_.id as id1_4_0_,
        student0_.stuName as stuName2_4_0_,
        student0_.university_id as universi3_4_0_
    from
        student student0_
    where
        student0_.id=?
Hibernate:
    select
        student0_.id as id1_4_0_,
        student0_.stuName as stuName2_4_0_,
        student0_.university_id as universi3_4_0_
    from
        student student0_
    where
        student0_.id=?
Hibernate:
    update
        student
    set
        university_id=?
    where
        id=?
Hibernate:
    update
        student
    set
        university_id=?
    where
        id=?

和第一个不一样！！

我在休眠注释中做错了什么，或者如果我的 JSON 注释中缺少某些内容，为什么第二个尝试工作。

更新：这是我的编辑服务。

@Override
@Transactional/*(propagation = Propagation.NESTED)*/
public T edit(T entity) throws Exception {
    return entityManager.merge(entity);
}

感谢任何帮助和建议。

【问题讨论】：

发布持久化数据的代码。
@Abdullah Khan 我更新了我的问题
您的映射错误。阅读 Hibernate 手册，了解如何正确映射双向 OneToMany 关联。
我在 hibernate 手册中有 JSON 序列化问题，我找不到解决方案来给我关于 JSON 序列化的正确解决方案，我已经问过这个stackoverflow.com/questions/46684015/…
JSON 序列化与 Hibernate 持久性完全无关。

标签： java spring hibernate spring-mvc jpa

【解决方案1】：

尝试像这样更新您的实体

@Entity
@Table(name = "university")
public class University extends BaseEntity {

    private String uniName;

    @OneToMany(mappedBy = "university", ...) // Check the mappedBy property
    private Collection<Student> students;

    //setters and getters

}

@Entity
@Table(name = "student")
public class Student extends BaseEntity {

    private String stuName;

    @ManyToOne(fetch = FetchType.EAGER)
    @JsonIgnoreProperties("students")
    private University university; // university is bidirectionally mapped to Student 

    //setters and getters
}

【讨论】：

我需要双方都急切地使用 JSON 序列化它有循环，如果我添加 @JsonIdentity 信息 json 序列化不符合我的要求
对于这个问题，使用不同的 DTO 类将您的 JSON 映射到方法参数。
请更具体一点
创建一个UserDTO.java 类，并在UserDTO.java 类中只包含您要序列化的特定用户字段。将您的 JSON 映射到 UserDTO.java 类而不是原始的 User 类。查看this 和this。
你的问题解决了吗？

【解决方案2】：

像下面这样更改我的实体后，它工作得很好。

大学.java

@Entity()
@Table(name = "university")
public class University extends BaseEntity {
    private String uniName;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval = true)
    @JoinColumn(name = "university_id")
    private Collection<Student> students;

    //setters and getters
}

学生.java

 @Entity
    @Table(name = "student")
    public class Student extends BaseEntity {
        private String stuName;

        @ManyToOne(fetch = FetchType.EAGER)
        @JoinColumn(name = "university_id",updatable = false,insertable = false)
        @JsonIgnoreProperties(value = "students", allowSetters = true)
        private University university;

        //setters and getters
    }

我希望这可以帮助遇到同样问题的其他人。

【讨论】：