Java中如何实现递归查询部门树形结构数据

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说明：在开发中，我们经常使用树形结构来展示菜单选项，如图：

那么我们在后端怎么去实现这样的一个功能呢？

1、数据库表：department

2、编写sql映射语句

         select * from department                                    and UpDepartmentCode=#{updepartmentcode}                                   

3、创建实体类

public class Department {    private String departmentcode;//部门code    private String departmentname;//部门名称    private String updepartmentcode="0";//上级部门    private String departmentdesc;//部门描述    private List childDept =new ArrayList();//部门信息树    public String getDepartmentcode() {        return departmentcode;    }    public void setDepartmentcode(String departmentcode) {        this.departmentcode = departmentcode == null ? null : departmentcode.trim();    }    public String getDepartmentname() {        return departmentname;    }    public void setDepartmentname(String departmentname) {        this.departmentname = departmentname == null ? null : departmentname.trim();    }    public String getUpdepartmentcode() {        return updepartmentcode;    }    public void setUpdepartmentcode(String updepartmentcode) {        this.updepartmentcode = updepartmentcode == null ? null : updepartmentcode.trim();    }    public String getDepartmentdesc() {        return departmentdesc;    }    public void setDepartmentdesc(String departmentdesc) {        this.departmentdesc = departmentdesc == null ? null : departmentdesc.trim();    }    public List getChildDept() {        return childDept;    }    public void setChildDept(List childDept) {        this.childDept = childDept;    }}

4、定义mapper

@Mapperpublic interface DepartmentMapper {    ListselectDepartmentTrees(Department department);    }

5、定义service业务层实现

@Service@Transactionalpublic class DepartmentImpl implements IDepartmentService {    @Resource    DepartmentMapper departmentMapper;        @Override    public List selectDepartmentTrees(Department department) {        return departmentMapper.selectDepartmentTrees(department);    }}

6、控制层实现

@RestController@RequestMapping("department")public class DepartmentController {    @Resource    IDepartmentService departmentService;    @Resource    IStationService stationService;    /**     * 查询所有部门 树形展示所有部门 包含模糊查詢     *     * @return     */    @RequestMapping("/treelist")    public Object selectAll(Department department) {        ModelMap map = new ModelMap();        try {            List departmentDtos = getDepartmentList(department);            map.put("msg", "查询部门成功");            map.put("data", departmentDtos);            map.put("code", 0);        } catch (Exception e) {            e.printStackTrace();            map.put("msg", "查询部门失败");            map.put("code", 1);        }        return map;    }    /**     * 递归查询部门     * @param department     * @return     */    private List getDepartmentList(Department department) {        List departments =departmentService.selectDepartmentTrees(department);        if (departments.size()>0){            Department department1=new Department();            for (int i = 0; i dtos=getDepartmentList(department1);                departments.get(i).setChildDept(dtos);            }        }        return departments;    }}

7、进行测试，这里我用postmain工具测试，结果如下图

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