@Data
public class OneSubject {
private String id;
private String title;
private List<TwoSubject> children = new ArrayList<>();
}


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@Data
public class TwoSubject {
private String id;
private String title;
}


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@GetMapping("getAllSubject")
public R getAllSubject(){
List<OneSubject> list = subjectService.getAllOneTwoSubject();
return R.Ok().data("list",list);
}


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// Course classification list （ Tree form ）
@Override
public List<OneSubject> getAllOneTwoSubject() {
//1 Query all first level classifications
QueryWrapper<EduSubject> wrapperOne = new QueryWrapper<>();
wrapperOne.eq("parent_id","0");
List<EduSubject> oneSubjectList = baseMapper.selectList(wrapperOne);
//2 Query all 2 Class classification
QueryWrapper<EduSubject> wrapperTwo = new QueryWrapper<>();
wrapperTwo.ne("parent_id","0");
List<EduSubject> twoSubjectList = baseMapper.selectList(wrapperTwo);
// establish list aggregate , Used to store the final encapsulated data
List<OneSubject> finalSubjectList = new ArrayList<>();
//3、 Package level 1 Classification
for (int i = 0; i < oneSubjectList.size(); i++) {
EduSubject eduSubject = oneSubjectList.get(i);
OneSubject oneSubject = new OneSubject();
BeanUtils.copyProperties(eduSubject,oneSubject);
// Loop through and query all the secondary classifications in the primary classification
// establish list The set encapsulates the secondary classification of each primary classification
List<TwoSubject> twoFinalSubjectList = new ArrayList<>();
for (int j = 0; j < twoSubjectList.size(); j++) {
EduSubject tSubject = twoSubjectList.get(j);
if(tSubject.getParentId().equals(oneSubject.getId())){
TwoSubject twoSubject = new TwoSubject();
BeanUtils.copyProperties(tSubject,twoSubject);
twoFinalSubjectList.add(twoSubject);
}
}
// Put all the secondary classifications below the first level into the first level
oneSubject.setChildren(twoFinalSubjectList);
finalSubjectList.add(oneSubject);
}
//4、 Packaging secondary classification
return finalSubjectList;
}


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import request from '@/utils/request'
export default {
//1 Course classification list
getSubjectList() {
return request({
url: '/eduservice/subject/getAllSubject',
method: 'get'
})
}
}


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<template>
<div class="app-container">
<el-input v-model="filterText" placeholder="Filter keyword" style="margin-bottom:30px;" />
<el-tree ref="tree2" :data="data2" :props="defaultProps" :filter-node-method="filterNode" class="filter-tree" default-expand-all />
</div>
</template>
<script>
import subject from '@/api/edu/subject'
export default {
data() {
return {
filterText: '',
data2: [], // Return all classified data
defaultProps: {
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