打印子类别列表，其中包含 JSON 响应中的类别

Question

我有这样的mysql表

https://i.stack.imgur.com/ON3JL.png

这是此表的实体类

Where(clause = "active =1")
@Entity
@Table(name = "category", catalog = "businessin")
public class Category implements java.io.Serializable {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "id", unique = true, nullable = false)
    private Integer id;
    private String name;
    private Integer parentId;
    private Integer active;
    private String pic;
    @JsonIgnore
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "category")
    private List<Product> products = new ArrayList<Product>();
    setters&getter 
}

我正在使用Spring Rest和Spring Data(jpaRepository(构建RESTful API。
我希望在将控制器的主要类别打印为 JSON 响应时，我希望它们还有一个子类别列表这个的例子

[
{
id: 1,
name: "Electronics",
parentId: 0,
active: 1,
pic: null
}]

对此

[
{
id: 1,
name: "Electronics",
parentId: 0,
active: 1,
pic: null
subCategories: [Mobile, Laptops]
}]

Answer 1

让你

的实体像这样很简单

@Where(clause = "active =1")
@Entity
@Table(name = "category" )
public class Category implements java.io.Serializable {

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "id", unique = true, nullable = false)
    private Integer id;
    private String name;
    @Column(nullable=false,columnDefinition="int default 1")
    private Integer active;
    private String pic;
    @JsonIgnore
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "category")
    private List<Product> products = new ArrayList<Product>();
    @ManyToOne
       @JoinColumn(name="parent_id")
       @JsonIgnore
   // @ColumnDefault("0")
    private Category parentId;
    @OneToMany(mappedBy="parentId")
    private List<Category> subCategories=new ArrayList<>();
setters and getters
}