Java后台返回数据实现多级分类树形结构

递归：

1：

 2：实体类

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Department {
        private Integer id;
        private String name;
        private Integer pid;
        private Integer status;
        private String desc;
        /**
         * 子目录列表
         */
        private List<Department> treeNode;
}

3：controller层

@RestController
@RequestMapping("/department")
@SuppressWarnings("all")
//@RequiredArgsConstructor(onConstructor = @__(@Autowired))
public class DepartmentController {

/* private final DepartmentService departmentService; */
    @Resource
    private  DepartmentService departmentService;
//    @PostMapping("treeDepartment")
//    public Result treeDepartment(){
//        List<Tree<String>> departmentAll = departmentService.findDepartmentAll();
//        return new Result(ResultCode.SUCCESS,departmentAll);
//    }


    @PostMapping("treeDepartment")
    public Result treeDepartment(){
        List<Department> departmentAll = departmentService.findDepartmentAll();
        return new Result(ResultCode.SUCCESS,departmentAll);
    }
}

4：service 层

@Service
public interface DepartmentService {
//    List<Tree<String>> findDepartmentAll();
    List<Department> findDepartmentAll();
}

实现类：主要逻辑

@Service
public class DepartmentSericeImpl implements DepartmentService {
    @Resource
    private DepartmentMapper departmentMapper;
    private static final String status = "status";
    private static final String desc = "desc";

    //    @Override
//    public List<Tree<String>> findDepartmentAll() {
//        List<Department> list = departmentMapper.findDepartmentAll();
//        List<Department> list2 = CollUtil.newArrayList();
//        //浅拷贝赋值
//        list2.addAll(list);
//        // rootId
//        String pid = "0";
//        //配置
//        TreeNodeConfig nodeConfig = new TreeNodeConfig();
//        // 自定义属性名 都要默认值的
//        //设置ID对应的名称
//        nodeConfig.setIdKey("id");
//        // 最大递归深度 3级目录
//        nodeConfig.setDeep(3);
        入参
        tree:  最终要返回的数据
        node:  lists数据
//
        返回
        Tree<String>
        Tree: 转换的实体 为数据源里的对象类型
        String: ID类型
//        //转换器
//        List<Tree<String>> treeList = TreeUtil.build(list2, pid, nodeConfig,
//                (node, tree) -> {
//            //id
//            tree.setId(node.getId().toString());
//            //姓名
//            tree.setName(node.getName());
//            //获取父节点id
//            tree.setParentId(node.getPid().toString());
//            // 扩展的属性 ...
//            tree.putExtra(status, node.getStatus());
//            tree.putExtra(desc, node.getDesc());
//        });
//        return treeList;
//    }
    @Override
    public List<Department> findDepartmentAll() {
        List<Department> departmentList = departmentMapper.findDepartmentAll();
        //将最终地查询结果存放到这个新地集合中
        List<Department> newDepartmentList = Lists.newArrayList();

        List<Integer> stringArrayList = new ArrayList<>();
        for (Department department : departmentList) {
            //存放部门编号
            stringArrayList.add(department.getId());
        }
        //判断查出来的数据是否为空
        for (Iterator<Department> iterator = departmentList.iterator(); iterator.hasNext(); ) {
            Department department = iterator.next();
            //判断departmentList  不包含部门父级id
            if (!stringArrayList.contains(department.getPid())) {
                recursionFn(departmentList, department);
                newDepartmentList.add(department);
            }
        }
        if (newDepartmentList.isEmpty()) {
            newDepartmentList = departmentList;
        }
        List<Department> finallDepartmentsList = newDepartmentList
                .stream()
                .filter(department -> {
            Integer pid = 0;
            return department.getPid().equals(pid);
        }).collect(Collectors.toList());
        return finallDepartmentsList;
    }

    private void recursionFn(List<Department> departmentList, Department department) {
        List<Department> childList = getChildList(departmentList, department);
        department.setTreeNode(childList);
        //在遍历的到子节点的数据，判断子节点下是否还存有子节点
        for (Department depart : childList) {
            //如果子节点中的数据依然拥有子节点,重新调用递归
            if (hasChild(departmentList, depart)) {
                recursionFn(departmentList, depart);
            }
        }

    }

    private List<Department> getChildList(List<Department> list, Department t) {
        ArrayList<Department> tlist = new ArrayList<>();
        //遍历集合中的数据
        Iterator<Department> iterator = list.iterator();
        while (iterator.hasNext()) {
            Department next = iterator.next();
            if (!StringUtils.isEmpty(next.getPid()) && next.getPid().equals(t.getId())) {
                tlist.add(next);
            }
        }
        return tlist;
    }

    /**
     * 判断是否有子节点
     */
    private boolean hasChild(List<Department> list, Department t) {
        return getChildList(list, t).size() > 0;
    }
}

5：mapper 层 以及xml文件

@Mapper
public interface DepartmentMapper {
    List<Department> findDepartmentAll();
}

xml.

    <select id="findDepartmentAll" resultType="com.example.demotest.pojo.Department">
        select * from department
    </select>

最终结果如下：