如何在JPA中Map复合主键

dzhpxtsq 于 2023-10-19 发布在其他

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@Table(name = "student")
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private long id;
    @Column(name = "roll_no", nullable = false)
    private long rollNo;
    @Column(name = "enrollment_no", nullable = false, unique = true)
    private String enrollmentNo;
}
   @Entity
   @Table(name = "subject")
   public class Subject {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private long id;
    @Column(name = "subject_code", nullable = false, unique = true)
    private String code;// course code
}

我有以上两个班级。我想为下面的数据库表student_marks（student_id，marks_id，marks，passing_status）创建一个StudentMarks类;
我尝试了这个

@Embeddable
public class StudentMarksId implements Serializable {
    private Long studentId;
    private Long subjected;
     //getter and setter
}
@Entity
@Table(name = "student_marks")
public class StudentMarks implements Serializable {
    private static final long serialVersionUID = 4428298147790767663L;
    @EmbeddedId
    @Id
    @JoinColumns({ 
        @JoinColumn(name = "subject_id", referencedColumnName = "id"),
            @JoinColumn(name = "student_id", referencedColumnName = "id") })
    private StudentMarksId id;
    
    private List<Subject> subjects;
    private List<Student> students;
    @Column(name = "marks", nullable = false)
    private int marks;
    @Column(name = "passing_status", nullable = false)
    private String passingStatus;// pass or fail
 }```
I want to map student and subjects to student_marks.

jpa

来源：https://stackoverflow.com/questions/77076019/how-to-map-composite-primary-key-in-jpa

1条答案

按热度按时间

owfi6suc1#

有几种方法可以Map这一点。一个是：

public class StudentMarksId implements Serializable {
    private Long studentId;
    private Long subjected;
     //getter and setter
}
@Entity
@Table(name = "student_marks")
@IdClass(StudentMarksId.class)
public class StudentMarks implements Serializable {
    private static final long serialVersionUID = 4428298147790767663L;
    @Id
    @ManyToOne
    @JoinColumn(name = "subject_id", referencedColumnName = "id")
    private Subject subject;
    @Id
    @ManyToOne
    @JoinColumn(name = "student_id", referencedColumnName = "id")
    private Student student;
    @Column(name = "marks", nullable = false)
    private int marks;
    @Column(name = "passing_status", nullable = false)
    private String passingStatus;// pass or fail
}

另一种可能是将StudentMarksId也Map为实体中的嵌入式：

@Embeddable
public class StudentMarksId implements Serializable {
    private Long studentId;
    private Long subjected;
     //getter and setter
}
@Entity
@Table(name = "student_marks")
@IdClass(StudentMarksId.class)
public class StudentMarks implements Serializable {
    private static final long serialVersionUID = 4428298147790767663L;
    @EmbeddedId
    private StudentMarksId id;
    @MapsId("subjected")
    @ManyToOne
    @JoinColumn(name = "subject_id", referencedColumnName = "id")
    private Subject subjects;
    @MapsId("studentId")
    @ManyToOne
    @JoinColumn(name = "student_id", referencedColumnName = "id")
    private Student student;
    @Column(name = "marks", nullable = false)
    private int marks;
    @Column(name = "passing_status", nullable = false)
    private String passingStatus;// pass or fail
}

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