外键未存储在子实体中(一对多)

Question

我对hibernate很新,并且偶然发现了这个我无法找到解决方案的问题.

当持久化父对象(与子对象具有一对多关系)时,此父对象的外键不存储在子表中.

我的课程:

Parent.java

@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;
    }
  }
}

Test.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)
  }
}

---

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.

到目前为止我唯一的解决方法是test2() - 先保持父级,然后是子级.

我的目标是在一次调用中将父级及其子级持久保存在父级上.有任何想法吗？

Answer 1

您还可以向父母添加额外的方法

public void addChild(Child child) 

这有点像

    child.setParent(this);

Answer 2

对于那种情况,我有一个很好的解决方案:D

mappedBy表示inverse ="true".所以你必须逆="假"

试试吧..

@OneToMany(fetch = FetchType.EAGER, cascade ={CascadeType.ALL})//javax.persistent.CascadeType
@JoinColumn(name = "parent_id")//parent's foreign key
public Collection<Child> getChildren() {
    return children;
}

我希望能成功