java后端递归循环取数（树形结构）

 哈喽！大家好,今天我们来看看树形结构的递归取数，说实话，这个呢，我其实也不太明白其中的原理，也就是我也不会灵活运用，之所以写下来，嘿嘿，是为了希望那行和我一样不会这个的，或者不懂这个递归的，可以有所帮助，然后，也方便那天我自己忘记了，查找起来也省力

一、测试Demo版

实体类

@Data
public class Dept implements Serializable {
    private int id;
    private int parentId;
    private String name;
    private List<Dept> child = new ArrayList<Dept>();

    public Dept(int id, int parentId, String name) {
        super();
        this.id = id;
        this.parentId = parentId;
        this.name = name;
    }

}

测试Test

public class TestDemo {
    private static List<Dept> deptList;

    static {
        Dept dept1 = new Dept(1, 0, "中国");
        Dept dept2 = new Dept(2, 1, "北京");
        Dept dept3 = new Dept(3, 1, "上海");
        Dept dept4 = new Dept(4, 1, "广东");
        Dept dept5 = new Dept(5, 4, "广州");
        Dept dept6 = new Dept(6, 4, "深圳");
        Dept dept7 = new Dept(7, 5, "天河区");
        deptList = new ArrayList<Dept>();
        deptList.add(dept1);
        deptList.add(dept2);
        deptList.add(dept3);
        deptList.add(dept4);
        deptList.add(dept5);
        deptList.add(dept6);
        deptList.add(dept7);
    }

    private static List<Dept> buildTree(List<Dept> deptList, int pid) {
        List<Dept> treeList = new ArrayList<Dept>();
        for (Dept dept : deptList) {
            if (dept.getParentId() == pid) {
                dept.setChild(buildTree(deptList, dept.getId()));
                treeList.add(dept);
            }
        }
        return treeList;
    }

    public static void main(String[] args) {
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("data", buildTree(deptList, 0));
        System.out.println(JSON.toJSONString(map));
    }

}

二、业务类型

1.实体类

@Data
public class PerMenuBO extends BaseVo {

    @ApiModelProperty(value = "自增主键ID")
    private Long id;

    @ApiModelProperty(value = "资源名称")
    private String name;

    @ApiModelProperty(value = "菜单权限标识")
    private String authorityTag;

    @ApiModelProperty(value = "前端跳转URL")
    private String path;

    @ApiModelProperty(value = "后端url")
    private String requestPath;

    @ApiModelProperty(value = "菜单组件")
    private String componet;

    @ApiModelProperty(value = "父菜单ID")
    private Long parentId;

    @ApiModelProperty(value = "图标")
    private String icon;

    @ApiModelProperty(value = "排序(默认1)")
    private Integer sort;

    @ApiModelProperty(value = "是否管控频次")
    private Boolean controlFrequency;

    @ApiModelProperty(value = "频次")
    private Integer frequency;

    @ApiModelProperty(value = "资源类型 （0:目录,1:菜单,2:按钮）")
    private Integer type;

    @ApiModelProperty(value = "逻辑删除标记(0:正常, 1:删除)")
    private Boolean delFlag;

    private List<PerMenuBO> child = new ArrayList<PerMenuBO>();
    
}

2.mapper类

public interface PerMenuMapper {

    List<PerMenuBO> getList(PerMenu model);
  
}

3.service类

public interface IPerMenuService {

     List<PerMenuBO> getListTree(PerMenuVO model);
  
}

 

4.serviceImpl类

@Service
public class PerMenuService extends AbstractBaseService implements IPerMenuService {

    @Autowired
    private PerMenuMapper perMenuMapper;

    @Override
    public List<PerMenuBO> getListTree(PerMenuVO model) {
        PerMenu param = copyProperties(model, PerMenu.class);
        List<PerMenuBO> list = perMenuMapper.getList(param);
        List<PerMenuBO> tree = buildTree(list, 0L);
        return tree;
    }

    public List<PerMenuBO> buildTree(List<PerMenuBO> list, Long pid) {
        List<PerMenuBO> listM = new ArrayList<PerMenuBO>();
        for (PerMenuBO menuBO : list) {
            if (menuBO.getParentId().equals(pid)) {
                menuBO.setChild(buildTree(list, menuBO.getId()));
                listM.add(menuBO);
            }
        }
        return listM;
    }
}

5.Controller类

@RestController
public class PerMenuController {

    @Autowired
    private IPerMenuService perMenuService;

    @PostMapping("/perMenu/getlisttree")
    @AutoLog(description = "递归查询资源菜单列表接口")
    @ApiOperation(value = "递归查询资源菜单列表接口")
    public BaseResponse<List<PerMenuBO>> getListTree(@RequestBody PerMenuVO request) {
        return new BaseResponse(true, "查询成功", 0, perMenuService.getListTree(request));
    }

}