树形数据展示

  BeanUtils.copyProperties(eduSubject, oneSubject); 将对象1数据复制到二中

 

第一步针对返回值数据创建对应的实体类

第二步两个实体类之间的表示关系（一级分类有多个二级分类）

//课程分类返回结构(树形)
@GetMapping("getAllSubject")
public R getAllSubject() {
    List<OneSubject> list = eduSubjectService.getAllOneTwoSubject();
    return R.ok().data("list", list);
}

//查询一级分类 parent_id=0
QueryWrapper<EduSubject> wrapperOne = new QueryWrapper<>();
wrapperOne.eq("parent_id", 0);
List<EduSubject> oneEduSubject = baseMapper.selectList(wrapperOne);

//查询二级分类 parent_id!=0
QueryWrapper<EduSubject> wrapperTwo = new QueryWrapper<>();
wrapperTwo.ne("parent_id", 0);
List<EduSubject> twoEduSubject = baseMapper.selectList(wrapperTwo);


//封装一级分类
List<OneSubject> oneList = new ArrayList<>();

for (int i = 0; i < oneEduSubject.size(); i++) {
    //遍历一级分类
    EduSubject eduSubject = oneEduSubject.get(i);
    //将一级分类eduSubject对象的值添加到OneSubject中
    OneSubject oneSubject = new OneSubject();
    //复制操作
    BeanUtils.copyProperties(eduSubject, oneSubject);
    oneList.add(oneSubject);


    //封装二级分类
    ArrayList<TwoSubject> twoList = new ArrayList<>();
    //遍历所有二级分类
    for (int m = 0; m < twoEduSubject.size(); m++) {
        EduSubject subject = twoEduSubject.get(m);
        TwoSubject twoSubject= new TwoSubject();
       //判断一级分类对应的二级分类数据，全表扫描
        if (subject.getParentId().equals(eduSubject.getId())){

            BeanUtils.copyProperties(subject, twoSubject);
            twoList.add(twoSubject);
        }
    }


   //添加一对多数据
    oneSubject.setChildren(twoList);


}




return oneList;