外键必须具有与多对一映射所引用的主键相同的列数 | 外键必须具有与多对一映射所引用的主键相同的列数

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问题描述

您好，下面是我的实体，它们之间具有多音素关联

Hi below is my entities with manytoone association between them

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 );


}

下面是我的2个表格中的列

below are the columns in my 2 table

student:

UserID
userrole

student_details:

VALUE
DESCRIPTION

"student_details"中的值"应输入到学生表的用户"中

the "value" in "student_details" should enter into "userrole" of student table

但是当我执行我的appmain时，我遇到了错误

but when I execute my appmain I am getting below error

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，但显示相同的错误请建议我如何解决这个问题

I tried to solve this but it showing same errorplease suggest me how to solve this

推荐答案

要解决此问题，请像这样更改代码:

To fix the issue, change your code like this:

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

    })
    private studentdetails userrole;

问题的原因:在映射中:

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

    })

您要告诉休眠在Student实体表中创建外键，该表称为userrole，该外键引用StudentDetails实体表中称为VALUE的列.

You are telling hibernate to create a foreign key in Student entity table called userrole that refers to the column called VALUE in StudentDetails entity table.

然后在下一行中，您再次告诉hibernate为StudentDetails中的列DESCRIPTION使用与FKey相同的列名-userrole，因此此行将覆盖上一行.

Then in next line you are again telling hibernate to use the same colum name - userrole as FKey for the column DESCRIPTION in StudentDetails, so this line overrides the previous one.

因此hibernate看到您正在尝试在Student实体表中将单个列作为外键映射到StudentDetails实体表.但是StudentDetails表具有由2列组成的复合键，因此休眠会抛出异常.

So hibernate sees that you are trying to have a single column as foreign key in Student entity table that maps to StudentDetails entity table. But the StudentDetails table has composite key made of 2 columns so hibernate throws an exception.

org.hibernate.MappingException: Foreign key (FK6D56043A4415BDB5:student [userrole])) must have same number of columns as the referenced primary key (student_details [VALUE,DESCRIPTION])

其他信息:

您正试图为实体StudentDetails声明一个复合ID，因此该实体应实现Serializable接口，这是强制性的.现在，此复合Id类应覆盖equals()和hashcode()方法.

You are trying to declare a composite Id for the entity StudentDetails, so this entity should implelemt Serializable interface and this is mandatory.Now this composite Id class should override equals() and hashcode() methods.

只是一个建议，请尝试为您的实体和字段遵循Java命名约定.

Just a suggestion, try to follow Java naming conventions for your entities and fields.

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