Java 树形结构组装的几种方式

 

1. 二级树数据结构

 

 

2. 结构组装

// 创建一级和二级的实体类
@Data
public class TwoSubject {
    private String id;
    private String title;
}

 

@Data
public class OneSubject {

    private String id;
    private String title;

    //一个一级分类有多个二级分类
    private List<TwoSubject> children = new ArrayList<>();
}

//课程分类列表（树形）
    @GetMapping("getAllSubject")
    public R getAllSubject() {
        //list集合泛型是一级分类
        List<OneSubject> list = eduSubjectService.getAllOneTwoSubject();
        return R.ok().data("list",list);
    }

    @Override
    public List<OneSubject> getAllOneTwoSubject() {
        //1. 查询一级目录
        QueryWrapper<EduSubject> wrapperOne = new QueryWrapper<>();
        wrapperOne.eq("parent_id","0");
        List<EduSubject> oneSubjectList = baseMapper.selectList(wrapperOne);
        //2. 查询二级目录
        QueryWrapper<EduSubject> wrapperTwo = new QueryWrapper<>();
        wrapperTwo.ne("parent_id",0);
        List<EduSubject> twoSubjectList = baseMapper.selectList(wrapperTwo);

        List<OneSubject> finalSubjectList = new ArrayList<>();

        //3. 封装一级
        oneSubjectList.forEach(o->{
            OneSubject oneSubject = new OneSubject();
            BeanUtils.copyProperties(o,oneSubject);
            finalSubjectList.add(oneSubject);

            List<TwoSubject> twoFinalSubjectList = new ArrayList<>();

            //4. 封装二级
            twoSubjectList.forEach(t->{
                if (t.getParentId().equals(o.getId())){
                    TwoSubject twoSubject = new TwoSubject();
                    BeanUtils.copyProperties(t,twoSubject);
                    twoFinalSubjectList.add(twoSubject);
                }
            });
            oneSubject.setChildren(twoFinalSubjectList);
        });
        return finalSubjectList;
    }

 

3. 使用swagger测试

{
  "success": true,
  "code": 20000,
  "message": "成功",
  "data": {
    "list": [
      {
        "id": "1178214681118568449",
        "title": "后端开发",
        "children": [
          {
            "id": "1178214681139539969",
            "title": "Java"
          },
          {
            "id": "1178585108407984130",
            "title": "Python"
          }
        ]
      },
      {
        "id": "1178214681181483010",
        "title": "前端开发",
        "children": [
          {
            "id": "1178214681210843137",
            "title": "JavaScript"
          },
          {
            "id": "1178585108454121473",
            "title": "HTML/CSS"
          }
        ]
      },
      {
        "id": "1178214681231814658",
        "title": "云计算",
        "children": [
          {
            "id": "1178214681252786178",
            "title": "Docker"
          },
          {
            "id": "1178214681294729217",
            "title": "Linux"
          }
        ]
      },
      {
        "id": "1178214681324089345",
        "title": "系统/运维",
        "children": [
          {
            "id": "1178214681353449473",
            "title": "Linux"
          },
          {
            "id": "1178214681382809602",
            "title": "Windows"
          }
        ]
      },
      {
        "id": "1178214681399586817",
        "title": "数据库",
        "children": [
          {
            "id": "1178214681428946945",
            "title": "MySQL"
          },
          {
            "id": "1178214681454112770",
            "title": "MongoDB"
          }
        ]
      },
      {
        "id": "1178214681483472898",
        "title": "大数据",
        "children": [
          {
            "id": "1178214681504444418",
            "title": "Hadoop"
          },
          {
            "id": "1178214681529610242",
            "title": "Spark"
          }
        ]
      },
      {
        "id": "1178214681554776066",
        "title": "人工智能",
        "children": [
          {
            "id": "1178214681584136193",
            "title": "Python"
          }
        ]
      },
      {
        "id": "1178214681613496321",
        "title": "编程语言",
        "children": [
          {
            "id": "1178214681626079234",
            "title": "Java"
          }
        ]
      }
    ]
  }
}

 

4.  三级树结构封装

 　　（1）组装结构

@Data
@TableName("pms_category")
public class CategoryEntity implements Serializable {
    private static final long serialVersionUID = 1L;

    /**
     * 分类id
     */
    @TableId
    private Long catId;
    /**
     * 分类名称
     */
    private String name;
    /**
     * 父分类id
     */
    private Long parentCid;
    /**
     * 层级
     */
    private Integer catLevel;
    /**
     * 是否显示[0-不显示，1显示]
     */
    private Integer showStatus;
    /**
     * 排序
     */
    private Integer sort;
    /**
     * 图标地址
     */
    private String icon;
    /**
     * 计量单位
     */
    private String productUnit;
    /**
     * 商品数量
     */
    private Integer productCount;

    @TableField(exist = false)
    List<CategoryEntity> children;

}

    @RequestMapping("/list/tree")
    //@RequiresPermissions("product:category:list")
    public R list(@RequestParam Map<String, Object> params){
        List<CategoryEntity> entities = categoryService.listWithTree();

        return R.ok().put("data", entities);
    }

    @Override
    public List<CategoryEntity> listWithTree() {
        //1、查出所有分类
        List<CategoryEntity> entities = baseMapper.selectList(null);

        //2、组装成父子的树形结构
        List<CategoryEntity> list = entities.stream().filter(categoryEntity ->
                categoryEntity.getParentCid() == 0)
                .map(menu -> {
                    menu.setChildren(getChildren(menu, entities));
                    return menu;
                })
                .sorted((m1, m2) -> {
                    return (m1.getSort() == null ? 0 : m1.getSort()) - (m2.getSort() == null ? 0 : m2.getSort());
                }).collect(Collectors.toList());
        return list;
    }

    private List<CategoryEntity> getChildren(CategoryEntity menu, List<CategoryEntity> all) {
        List<CategoryEntity> childrenList = all.stream().filter(categoryEntity -> categoryEntity.getParentCid() == menu.getCatId())
                .map(m -> {
                    //1. 找到子菜单
                    m.setChildren(getChildren(m, all));
                    return m;
                }).sorted((m1, m2) -> {
                    //2、菜单的排序
                    return (m1.getSort() == null ? 0 : m1.getSort()) - (m2.getSort() == null ? 0 : m2.getSort());
                }).collect(Collectors.toList());
        return childrenList;
    }

　　测试结果

 

5.  hutool工具TreeUtil

　　https://doc.hutool.cn/pages/TreeUtil/#%E4%BB%8B%E7%BB%8D

 

6. 使用子id查询父id

　　在实现类中传入子id，使用递归查询

    @Override
    public Long[] findCatelogPath(Long catelogId) {
        List<Long> paths = new ArrayList<>();
        List<Long> parentPath = findParentPath(catelogId, paths);
        Collections.reverse(parentPath);
        return parentPath.toArray(new Long[parentPath.size()]);
    }
    private List<Long> findParentPath(Long catelogId,List<Long> paths){
        //1、收集当前节点id
        paths.add(catelogId);
        CategoryEntity byId = this.getById(catelogId);
        if(byId.getParentCid()!=0){
            findParentPath(byId.getParentCid(),paths);
        }
        return paths;
    }

　　测序结果

@Test
    public void contextLoads() {
        Long[] catelogPath = categoryService.findCatelogPath(165L);
        log.info("完整路径,{}", Arrays.asList(catelogPath));
    }

　　完整路径,[1, 22, 165]