java - 我们如何通过Jpa获取完整的分层数据列表

Question

作为我们数据端的需求，有一个mysql表结构如下:

id  category_id category_name   parent_id   delete_status
 3  145         Lip Makeup      123           0
 2  134         Face Makeup     123           0
 1  123         Makeup          0             0

数据结构像树，重新编码 id = 1 是其他 2 条记录(id = 2 和 id = 3)的父亲。连接列是parent_id，映射DTO是:

@Entity
@Data
@Table(name = "category_tab")
public class CategoryDto {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id", unique = true, nullable = false, length = 20)
private long id;

@Column(name = "category_id", nullable = false)
Long categoryId;

@Column(name = "category_name", nullable = false)
String name;

@Column(name = "parent_id", nullable = false)
Long parentId;

@Column(name = "delete_status", nullable = false)
Integer deleteStatus;

@OneToMany(fetch = FetchType.LAZY)
@JoinColumn(name = "parent_id", insertable = false, updatable = false)
private Set<CategoryDto> children = new HashSet<>();

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    ShopeeCategoryDto that = (ShopeeCategoryDto) o;
    return Objects.equals(categoryId, that.categoryId) &&
            Objects.equals(name, that.name);
}

@Override
public int hashCode() {
    return Objects.hash(categoryId, name);
}}

现在我想获取 CategoryDto 的完整列表，其中包含其子列表，因为随后可以轻松处理它。就像 DaoImpl:

List<CategoryDto> fetchAll();

那么这个方法应该怎么实现呢？我用的是spring boot + Jpa框架

Answer 1

@Query("select category from CategoryDto category where category.deleteStatus != ?1")
CategoryDto findAllBydeleteStatus(Integer deleteStatus);

文档:https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#jpa.query-methods.query-creation