带有连接 table 的双向 @ManyToOne 创建重复键

Question

我正在实施 @ManyToOne 双向关系与 join table 使用 hibernate，但是当我保留一些数据时，hibernate 声称关系 table 中的记录被插入两次，违反了唯一约束，因为错误下面的消息显示：

ERROR: org.hibernate.engine.jdbc.spi.SqlExceptionHelper - ERROR: duplicate key value violates unique constraint "tillage_sample_pkey"
Detail: Key (id_tillage, id_sample)=(82, 110) already exists.

我有以下 tables:

Tillage(id,其他一些数据)(一个Tillage可以有多个样本)
Sample (id, some other data) (一个Sample只能有一个Tillage)
tillage_sample (id_tillage, id_sample) PK (id_tillage, id_sample)

当我创建一个 Tillage 对象时，我填充了一个 Sample。在 Sample 对象中，我指向 Tillage 对象，创建一个 "double binding"。

我猜是这个“double bind”造成了麻烦，因为 Tillage/Sample 关系在保存耕作时由 hibernate 保留并重复该步骤尝试将耕作保留在样本中（这是同一个耕作对象）。

这是我的代码，以帮助您理解我的问题：

Tillage.java

@Entity
@Table(name = "tillage")
public class Tillage implements Serializable {

private static final long serialVersionUID = 3605331584324240290L;

@Id
@GeneratedValue(generator = "tillage_id_seq", strategy = GenerationType.SEQUENCE)
@SequenceGenerator(name = "tillage_id_seq", sequenceName = "tillage_id_seq", allocationSize = 1)
private Integer id;

@Column(name = "name")
private String name;
// Other simple attributes

@ManyToOne
@JoinColumn(name = "id_farm")
@JsonBackReference
private Farm farm;

// This relation is the problematic one
@OneToMany(cascade=CascadeType.ALL, fetch = FetchType.EAGER)
@JoinTable(name = "tillage_sample",
           joinColumns = { @JoinColumn(name = "id_tillage") }, 
           inverseJoinColumns = {@JoinColumn(name = "id_sample") })
private List<Sample> sampleList;

// Although similar, this one is doing OK
@ManyToMany(fetch = FetchType.EAGER)
@JoinTable(name = "tillage_owner", 
           joinColumns = { @JoinColumn(name = "id_tillage") }, 
           inverseJoinColumns = {@JoinColumn(name = "id_owner") })
private List<Owner> ownerList;

// getters & setters
}

Sample.java

@Entity
@Table(name = "sample")
public class Sample implements Serializable {

private static final long serialVersionUID = 7064809078222302493L;

@Id
@GeneratedValue(generator = "sample_id_seq", strategy = GenerationType.SEQUENCE)
@SequenceGenerator(name = "sample_id_seq", sequenceName = "sample_id_seq", allocationSize = 1)
private Integer id;

@Column(name = "name")
private String name;
// Other simple attributes

// This completes the relation Tillage-Sample
@ManyToOne(cascade=CascadeType.ALL, fetch = FetchType.EAGER)
@JoinTable(name = "tillage_sample", 
   joinColumns = { @JoinColumn(name = "id_sample") }, 
   inverseJoinColumns = {@JoinColumn(name = "id_tillage") })
private Tillage tillage = new Tillage();

@OneToMany(cascade=CascadeType.ALL, fetch=FetchType.EAGER)
@JoinTable(name = "sample_sample_item", 
           joinColumns = { @JoinColumn(name = "id_sample") }, 
           inverseJoinColumns = {@JoinColumn(name = "id_sample_item") })
private List<SampleItem> sampleItemList;


// Getters and Setters  
}

SomeService.java

...
@Override
public Tillage toTillage(TillageDTO dto) {

    Tillage tillage = new Tillage();
    tillage.setName(dto.getNameTillage());

    // Fill the samples of the tillage
    for(ArrSample sample : dto.getSamples().getArrSample()){

        Sample s = new Sample();
        s.setName(sample.getName());

        // Setting the tillage in the Sample object
        s.setTillage(tillage);

        // Fill the items of the sample
        for(Array arr : sample.getAreas().getArray()){

            SampleItem si = new SampleItem();

            si.setProduction(Double.parseDouble(arr.getProduction()));

            // Double binding between sample and sampleItem
            si.setSample(s);
            s.getSampleItemList().add(si);
        }
        // Adding a sample to Tillage
        tillage.getSampleList().add(s);
    }
    return tillage;
}


public void save(TillageDTO dto){
    Tillage t = this.toTillage(dto);

    // The error occurs when we persist the data
    // The entityManager is Autowired by Spring and works in other places
    entityManager.persist(tillage);

}

Answer 1

这不是双向 OneToMany。使用相同的联接 table.

的单向关联太独立了

在双向关联中，一侧必须与另一侧相反。对于 OneToMany，单边必须是反面：

@OneToMany(mappedBy = "tillage", cascade=CascadeType.ALL, fetch = FetchType.EAGER)
private List<Sample> sampleList;

带有连接 table 的双向 @ManyToOne 创建重复键

Bidirectional @ManyToOne with join table creates duplicate key

java

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hibernate-onetomany