从mysql查询菜单表用java生成菜单树

做的时候采用的框架是springboot+jpa

菜单表如下：

菜单实体：

@Entity@Table(name = "t_sys_menu")public class SysMenuDTO{    private Long id;     private String name; //菜单名称    private Long parentId; //父菜单id    @Transient    private List<SysMenuDTO> childMenu = new ArrayList<SysMenuDTO>();    //setter/getter略}

Controller层（运用了swagger-ui）:

@RestController@RequestMapping("/api/sys/menu")public class MenuController extends BaseController{    @Autowired    private MenuBO menuBO;/**     * 菜单树,根据传入的菜单id查询该菜单下的所有子菜单     * @param menuId     * @return     */    @RequestMapping(value = "/getMenuTree",method = RequestMethod.GET)    @ApiOperation(value = "菜单树",notes="菜单树")    @ApiImplicitParams({            @ApiImplicitParam(name = "menuId",value = "菜单id",dataType = "Long",paramType = "query")    })    @ApiResponses(value = {@ApiResponse(code = 200,message = "菜单树")})    public JsonMessage<String> getMenuTree(@RequestParam(value = "menuId",required = false) Long menuId)      {      return JsonMessage.successed(JsonUtil.toDefaultJSONString(menuBO.generateTreeNode(menuId),null));    }}

Service层：

@Servicepublic class MenuBo{  @Autowired    private SysMenuBO sysMenuBO;    /**     * 生成菜单树     * @param rootId     * @return     */    public SysMenuDTO generateTreeNode(Long rootId){        SysMenuDTO root = null;        List<SysMenuDTO> childrenTreeNode = new ArrayList<>();        if (rootId != null){            root = sysMenuBO.findOne(rootId); //根据id查询父菜单对象            childrenTreeNode = this.getChildNode(rootId); //查询子菜单对象        }else {            root = sysMenuBO.findOne(new NumberCondition("parentId",0,NumberCondition.Handler.EQUAL));            childrenTreeNode = this.getChildNode(root.getId());        }        for (SysMenuDTO item:childrenTreeNode){            SysMenuDTO node = this.generateTreeNode(item.getId());            root.getChildMenu().add(node);        }        return root;    }    /**     * 查询所有子菜单     * @param nodeId     * @return     */    public List<SysMenuDTO> getChildNode(Long nodeId){    //根据父id查询所有子菜单        List<SysMenuDTO> childNodeList = sysMenuBO.findAll(new NumberCondition("parentId",nodeId,NumberCondition.Handler.EQUAL));       if(childNodeList .size()==0){            return null;        }         return childNodeList ;    }}

SysMenuBO继承自BaseBO,BaseBO里面有封装好的查询方法

public class BaseBO<T extends AbstractBaseDTO,K extends Serializable> {    @PersistenceContext    public EntityManager em;    @Autowired    public BaseDAO<T,K> repository;    @Transactional    public void deleteAll(){        repository.deleteAll();    }     public List<T> findAll(BaseCondition condition){        Specification<T> specification= ConditionUtil.getSpecificationByCondition(condition);        return repository.findAll(specification);    }     public T findOne(K k){        return repository.findOne(k);    }    public T findOne(BaseCondition condition){        Specification<T> specification= ConditionUtil.getSpecificationByCondition(condition);        return repository.findOne(specification);    }}

当然也可以自己在DAO层里写查询方法。
这样返回的结果就是：

• 首页
  
  • 系统管理
    
    • 用户管理
      
      • 新增用户
    • 角色管理

这样返回的是一个对象