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我正在使用 Hibernate 和 OneToMany 关系，我今天遇到了一个奇怪的行为，虽然我是故意这样做的，但我没想到这种行为

学院.java

@Entity
@Table(name="COLLEGE")
public class College implements Serializable{
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="COLLEGE_XID")
    private Long collegeId;

    @Column(name="COLLEGE_NAME")
    private String collegeName;

    @OneToMany(mappedBy="college",cascade = CascadeType.ALL) 
    private List<Student> studentList = new ArrayList<Student>();
    //... with get and setters
}

学生.java

@Entity
@Table(name = "STUDENT")
public class Student implements Serializable    {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Column(name="STUDENT_XID")
    private Long studentId;

    @Column(name="STUDENT_NAME")
    private String studentName;

    @ManyToOne
    @JoinColumn(name="COLLEGE_XID",nullable=false)
    private College college;
    //... with get and setters
}

应用程序.java

    College college1 = new BdCollege();
    college1.setCollegeName("C_1");

    College college2 = new BdCollege();
    college2.setCollegeName("C_2");

    Student student1 = new BdStudent();
    student1.setStudentName("S_1_C_2");

    CollegeDAO collegeDAO = new  CollegeDAO();

    // setting student 1 Parent to College 1        
    student1.setCollege(college1);   // <---- Here the Issue  ... student 1 as college 1 child

    // BUT assigning Student 1 as Child of Collge 2 in List 
    // i did it purposely to test the behaviour
    college2.getStudentList().add(student1);  // <---- Here the Issue ... but assigning it in the list of College 2 ... ws expecting Exception 

     // Saved College 1 & 2
     collegeDAO.save(college1);
     collegeDAO.save(college2);

      // Saved Successfully BUT

结果学院表

 COLLEGE_XID     COLLEGE_NAME    
 --------------  --------------- 
 1               C_1             
 2               C_2

学生桌

 STUDENT_XID     STUDENT_NAME     COLLEGE_XID    
 --------------  ---------------  -------------- 
 1               S_1_C_2          1

我期待一些例外，因为孩子和父母在大学里的分配不匹配 - 学生的例子和另一个让我困扰的事情是hibernate生成的查询

Hibernate: insert into COLLEGE (COLLEGE_NAME) values (?)
Hibernate: insert into COLLEGE (COLLEGE_NAME) values (?)
Hibernate: insert into STUDENT (COLLEGE_XID, STUDENT_NAME) values (?, ?)

即它首先保存College 1，然后是College 2，然后将学生保存为College 2 的子级，但结果显示为College 1 的子级

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1 回答 1

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这是因为您添加了 mappedBy 属性并使学生成为关联的所有者。由于 Student 实体是所有者，它将保持关系，hibernate 将忽略 College 方面的变化。

于 2014-07-17T06:47:21.067 回答