外键未存储在子实体中(一对多) [英] Foreign key not stored in child entity (one-to-many)

问题描述

我对 hibernate 很陌生，偶然发现了这个问题，我找不到解决方案.

I'm quite new to hibernate and have stumbled on this problem, which I can't find solution for.

在持久化父对象时(与子对象具有一对多关系)，此父对象的外键不会存储在子对象表中.

When persisting parent object (with one-to-many relationship with child), the foreign-key to this parent is not stored in child's table.

我的课程:

@javax.persistence.Table(name = "PARENT")
@Entity
public class PARENT {
  private Integer id;

  @javax.persistence.Column(name = "ID")
  @Id
  @GeneratedValue(strategy=GenerationType.AUTO)
  public Integer getId() {
    return id;
  }

  public void setId(Integer id) {
    this.id = id;
  }

  private Collection<Child> children;

  @OneToMany(mappedBy = "parent", fetch = FetchType.EAGER, cascade = {CascadeType.ALL})
  @Cascade({org.hibernate.annotations.CascadeType.ALL})
  public Collection<Child> getChildren() {
    return children;
  }

  public void setChildren(Collection<Child> children) {
    this.children = children;
  }
}

Child.java

@javax.persistence.Table(name = "CHILD")
@Entity
@IdClass(Child.ChildId.class)
public class Child {
  private String childId1;

  @Id
  public String getChildId1() {
    return childId1;
  }

  public void setChildId1(String childId1) {
    this.childId1 = childId1;
  }

  private String childId2;

  @Id
  public String getChildId2() {
    return childId2;
  }

  public void setChildId2(String childId2) {
    this.childId2 = childId2;
  }

  private Parent parent;

  @ManyToOne
  @javax.persistence.JoinColumn(name = "PARENT_ID", referencedColumnName = "ID")
  public Parent getParent() {
    return parent;
  }

  public void setParent(Operation parent) {
    this.parent = parent;
  }

  public static class ChildId implements Serializable {
    private String childId1;

    @javax.persistence.Column(name = "CHILD_ID1")
    public String getChildId1() {
      return childId1;
    }

    public void setChildId1(String childId1) {
      this.childId1 = childId1;
    }

    private String childId2;

    @javax.persistence.Column(name = "CHIILD_ID2")
    public String getChildId2() {
      return childId2;
    }

    public void setChildId2(String childId2) {
      this.childId2 = childId2;
    }

    public ChildId() {
    }

    @Override
    public boolean equals(Object o) {
      if (this == o) return true;
      if (o == null || getClass() != o.getClass()) return false;

      ChildId that = (ChildId) o;

      if (childId1 != null ? !childId1.equals(that.childId1) : that.childId1 != null) 
        return false;
      if (childId2 != null ? !childId2.equals(that.childId2) : that.childId2 != null)
        return false;

      return true;
    }

    @Override
    public int hashCode() {
      int result = childId1 != null ? childId1.hashCode() : 0;  
      result = 31 * result + (childId2 != null ? childId2.hashCode() : 0);
      return result;
    }
  }
}

测试.java

public class Test() {

  private ParentDao parentDao;

  public void setParentDao(ParentDao parentDao) {
    this.parentDao = parentDao;
  }

  private ChildDao childDao;

  public void setChildDao(ChildDao childDao) {
    this.childDao = parentDao;
  }

  test1() {
    Parent parent = new Parent();

    Child child = new Child();
    child.setChildId1("a");
    child.setChildId2("b");
    ArrayList<Child> children = new ArrayList<Child>();
    children.add(child);

    parent.setChildren(children);
    parent.setValue("value");

    parentDao.save(parent); //calls hibernate's currentSession.saveOrUpdate(entity)
  }

  test2() {
    Parent parent = new Parent();
    parent.setValue("value");
    parentDao.save(parent); //calls hibernate's currentSession.saveOrUpdate(entity)

    Child child = new Child();
    child.setChildId1("a");
    child.setChildId2("b");
    child.setParent(parent);
    childDao.save(); //calls hibernate's currentSession.saveOrUpdate(entity)
  }
}

<小时>

调用 test1() 时，两个实体都会写入数据库，但 CHILD 表中的字段 PARENT_ID 保持为空.

---

When calling test1(), both entities get written to database, but field PARENT_ID in CHILD table stays empty.

到目前为止我唯一的解决方法是 test2() - 先保留父级，然后是子级.

The only workaround I have so far is test2() - persisting parent first, and then the child.

我的目标是在 Parent 上对 save() 的一次调用中保留父级及其子级.有什么想法吗?

My goal is to persist parent and its children in one call to save() on Parent. Any ideas?

推荐答案

你也可以像

public void addChild(Child child) 

做类似的事情

    child.setParent(this);

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