Java 双向@ManyToOne与联接表一起创建重复键

我使用hibernate实现了一个@ManyToOne双向关系和一个连接表，但是当我保存一些数据时，hibernate声称关系表中的记录被插入了两次，违反了唯一约束，如下面的错误消息所示：

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.

我有以下表格：

• 耕作（id，其他一些数据）（一次耕作可以有多个样本）
• 样本（id，一些其他数据）（一个样本只能进行一次耕作）
• 耕作样本（id_耕作，id_样本）PK（id_耕作，id_样本）

当我创建一个耕作对象时，我会填充一个样本。在示例对象中，我指向耕作对象，创建一个“双绑定”

我猜这个“双绑定””是造成问题的原因，因为当hibernate保存耕作时，耕作/样本关系由hibernate保持，当它试图在样本（即同一耕作对象）内保持耕作时，重复该步骤

下面是我的代码，以帮助您了解我的问题：

tilling.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
}

@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  
}

...
@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);

}

---

那不是一个双向的单亲家庭。使用同一个联接表的单向关联太多了

在双向关联中，一侧必须与另一侧相反。对于单面婚姻，单面必须是反面：

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

@OneToMany（mappedBy=“tillage”，cascade=CascadeType.ALL，fetch=FetchType.EAGER）
私人名单样本名单；

完美！我认为mappedBy仅用于使用联接列的关联。谢谢