play框架中同一个实体类的一对多

Question

美好的一天!我总是得到一个错误,以保存我的实体模型

Error inserting bean [class models.CategoryEntity] with unidirectional relationship. For inserts you must use cascade save on the master bean [class models.CategoryEntity].]

在这里我的课

@Entity
public class CategoryEntity extends Model {
    @Id
    private String categoryId;

    private String Name;
    private Integer level;

    @OneToMany(targetEntity = CategoryEntity.class, cascade = CascadeType.ALL)
    private List<CategoryEntity> categories;
//GETERS SETRES
}

我试图保存标题类别,但错误是相同的

Answer 1

如果我正确理解了这个问题,你想要的是每个CategoryEntity包含其他CategoryEntities的列表,我会想到两种可能的方法(尽管它们都没有使用@OneToMany):

方法1:
您可以创建@ManyToMany关系并定义@JoinTable,同时命名其键:

@Entity
public class CategoryEntity extends Model {
    @Id
    private String categoryId;

    private String name;
    private Integer level;

    @ManyToMany(cascade=CascadeType.ALL)
    @JoinTable(         name = "category_category",
                 joinColumns = @JoinColumn(name = "source_category_id"), 
          inverseJoinColumns = @JoinColumn(name = "target_category_id"))
    public List<CategoryEntity> category_entity_lists = new ArrayList<CategoryEntity>();
}

方法2:
或者您可以为类别实体列表创建新实体并创建@ManyToMany关系,例如:

@Entity
public class CategoryList extends Model
{
    @Id
    public Long id;

    @ManyToMany
    @JoinTable(name="categorylist_category")
    public List<CategoryEntity> category_list = new ArrayList<CategoryEntity>();
}

然后在你的模型中:

@Entity
public class CategoryEntity extends Model {
    @Id
    private String categoryId;

    private String name;
    private Integer level;

    @OneToOne
    public CategoryList this_category_list;

    @ManyToMany(mappedBy="category_list")
    public List<CategoryList> in_other_category_lists = new ArrayList<CategoryList>();
}

没有测试代码,但是应该做的是每个CategoryEntity都可以是几个CategoryLists的一部分.每个CategoryList都包含CategoryEntities列表.

您必须初始化this_category_list并将CategoryEntities添加到其category_list字段.