Question

我使用spring boot，使用jpa（hibernate）和postgresql

我使用复合键。

@Entity
@IdClass(SamplingsPK.class)
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class Samplings {

    @Id
    @GeneratedValue
    private Integer id;

    @Id
    private int year;

    @OneToMany(mappedBy = "sampling", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Samples> samples = new ArrayList<>();
   ...
}

public class SamplingsPK implements Serializable {

    private Integer id;

    private int year;

    public SamplingsPK(Integer id, int year) {
        this.id = id;
        this.year=year;
    }

    private SamplingsPK(){

    } 

    @PrePersist
    public void prePersist() {
        year = LocalDate.now().getYear();
    }
}   

@Entity
public class Samples {
    @Id
    @SequenceGenerator(name = "samples_id_seq", sequenceName = "samples_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "samples_id_seq")
    private Integer id;

    private String sampleLetter;

    @ManyToOne
        @JoinColumns({
            @JoinColumn(name = "sampling_id", referencedColumnName = "id"),
            @JoinColumn(name = "sampling_year", referencedColumnName = "year")
        })
private Samplings sampling;

}

工作正常

我希望有一个复合键，而不是样本中的序列...... SamplingsPK + sampleLetter。

是否可以这样做，如何保存样品？

Answer 1

这是“派生身份”，因此Samples可以使用@IdClass映射，如下所示：

@Entity
@IdClass(SamplesPK.class)
public class Samples {
    @Id
    @ManyToOne
    @JoinColumns({
        @JoinColumn(name = "sampling_id", referencedColumnName = "id"),
        @JoinColumn(name = "sampling_year", referencedColumnName = "year")
    })
    private Samplings sampling;

    @Id
    private String sampleLetter;
}

public class SamplesPK {
    SamplingsPK sampling; // matches name of attribute and type of Samplings PK
    String sampleLetter; // matches name and type of attribute
}

在第2.4.1节的JPA 2.2 spec中讨论派生身份（带示例）。

为子项+新字段重用复合键

1 个答案: