Question

下面是我的实体，他们之间有很多关联

student.java

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

    @Id
    @Column(name = "UserID")
    private String userid;

    @ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.LAZY)
    @JoinColumns({
       @JoinColumn(name = "userrole", referencedColumnName = "VALUE"),
       @JoinColumn(name = "userrole", referencedColumnName = "DESCRIPTION")

    })
    private studentdetails userrole;

//setters and getters 
//constructor

}

studentdetails.java

@Data
@Entity
@Table(name = "student_details")
public class studentdetails {

    @Id
    @Column(name = "VALUE")
    private String value;

    @Id
    @Column(name = "DESCRIPTION")
    private String description;

   //setters and getters 
   //constructor
}

appmain.java

public static void main()
{

//session configuration

studentdetails  sd = new studentdetails();
sd.setvalue("abc");
sd.setdescription("abcdef");

student student1 = new student();
student.setuserid("1");
student.userrole(sd);

student student2 = new student();
student.setuserid("2");
student.userrole(sd);

session.save(student1 );
session.save(student2 );


}

下面的

是我的2表中的列

student: 

UserID
userrole

student_details:

VALUE
DESCRIPTION

“student_details”中的“value”应该输入学生表的“userrole”

但是当我执行我的appmain时，我收到了错误

org.hibernate.MappingException: Foreign key (FK6D56043A4415BDB5:student [userrole])) must have same number of columns as the referenced primary key (student_details [VALUE,DESCRIPTION])
    at org.hibernate.mapping.ForeignKey.alignColumns(ForeignKey.java:113)
    at org.hibernate.mapping.ForeignKey.alignColumns(ForeignKey.java:96)
    at org.hibernate.cfg.Configuration.secondPassCompileForeignKeys(Configuration.java:1354)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1261)
    at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:383)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1377)
    at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:954)

我试图解决此问题，但它显示相同的错误请建议我如何解决这个问题

Answer 1

要解决此问题，请更改以下代码：

 @ManyToOne(cascade = CascadeType.ALL,fetch = FetchType.LAZY)
    @JoinColumns({
       @JoinColumn(name = "userrole_value", referencedColumnName = "VALUE"),
       @JoinColumn(name = "userrole_desc", referencedColumnName = "DESCRIPTION")

    })
    private studentdetails userrole;

问题原因：在映射中：

@JoinColumns({
       @JoinColumn(name = "userrole", referencedColumnName = "VALUE"),
       @JoinColumn(name = "userrole_desc", referencedColumnName = "DESCRIPTION")

    })

您告诉hibernate在名为Student的{{1}}实体表中创建一个外键，该表引用userrole实体表中名为VALUE的列。

然后在下一行中，您再次告诉hibernate使用相同的列名称StudentDetails作为userrole中DESCRIPTION列的FKey，因此该行会覆盖前一行。< / p>

所以hibernate看到你试图在映射到StudentDetails实体表的Student实体表中将单个列作为外键。但StudentDetails表的复合键由2列组成，因此hibernate会抛出异常。

StudentDetails

其他信息：

您正在尝试为实体org.hibernate.MappingException: Foreign key (FK6D56043A4415BDB5:student [userrole])) must have same number of columns as the referenced primary key (student_details [VALUE,DESCRIPTION])声明一个复合ID，因此该实体应该实现StudentDetails接口，这是必需的。现在，此复合Id类应覆盖Serializable和equals()方法。

只是一个建议，尝试遵循您的实体和字段的Java命名约定。

对于manytoone映射，外键必须具有与引用的主键相同的列数

1 个答案: