经验+9:Java递归查询子父级表
基于JPA进行演示
Entity层
@Entity
@DynamicInsert
@DynamicUpdate
@Data
@Table(name = "t_menu")
public class Menu {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private Integer parentId;//父id
private String name;//名称
@Transient
private List<Menu> children;//子集
public Menu generateTree(Integer id, List<Menu> list) {
Menu root = new Menu();
//查询根
for (Menu menu : list) {
if (menu.getId() == id) {
root = menu;
}
}
//查询子集
List<Menu> childList = new ArrayList<>();
for (Menu node : list) {
if (node.getParentId() == root.getId()) {
childList.add(node);
}
}
//子集查询子集
if (childList != null && childList.size() > 0) {
for (Menu child : childList) {
Menu childRoot = generateTree(child.getId(), list);
if (root.getChildren() == null) {
root.setChildren(new ArrayList<>());
}
root.getChildren().add(childRoot);
}
}
return root;
}
}
Dao层
@Repository
public interface MenuRepository extends PagingAndSortingRepository<Menu, Integer>, JpaSpecificationExecutor<Menu>, CrudRepository<Menu, Integer> {
@Query("from Menu")
List<Menu> findList(); // 查询表所有数据
}
Controller层
@RestController
public class MenuController {
@Autowired
private MenuRepository menuRepository;
@GetMapping("/getTree")
public Menu t1() {
List<Menu> list = menuRepository.findList();
Menu menu = new Menu().generateTree(0, list); // 0为根节点id
return menu;
}
}
// 返回结果
{
"id": 0,
"parentId": -1,
"name": "虚拟商品",
"children": [
{
"id": 3,
"parentId": 0,
"name": "卡密",
"children": null
},
{
"id": 4,
"parentId": 0,
"name": "充值",
"children": null
}
]
}