Java后台返回实现前端树形结构数据

我不是女神ヾ 2023-10-03 21:42 51阅读 0赞

## Java后台如何返回实现前端树形结构数据： ##

### 1.步（必须这样写）： ###

package com.zhecre.jx.business.common;
    
    import lombok.AllArgsConstructor;
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    import java.util.List;
    
    /**
     * 该类为树形结构的泛型类,所有使用TreeUtil的List集合中泛型都需要继承该类
     */
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class BaseTreeNode<T> {
        
        /**
         * 子Id
         */
        private String indexid;
    
        private String indexname;//指标名字
        /**
         * 父ID ,若parentId等于0 或者null,表示为顶级
         */
        private String parentid;
        /**
         * 子节点
         */
        private List<T> children;
    
    }

### 2步： ###

package com.zhecre.jx.business.model.cases.response;
    
    import com.zhecre.jx.business.common.BaseTreeNode;
    import lombok.Data;
    
    import java.util.List;
    
    /**
     * 描述：补偿方案管理新增指标配置三级下拉
     *
     */
    @Data
    public class AreaInfo extends BaseTreeNode<AreaInfo> {
        
    
        private String indexid;//指标ID
    
        private String indexname;//指标名字
    
        private String  unit;
    
        private Double coef;
    
        private String parentid;//上一级指标pid
    
    
        /** 子节点 */
        private List<AreaInfo> children;
    
    
    
    }

### 3.controller ###

@GetMapping("/compensationtree")
        public List<AreaInfo> areaInfoList(){
        
            //首次查所有节点数据
            List<AreaInfo> areaInfu = pasCaseService.selectAll();
            List<AreaInfo> tree = TreeUtil.getTree(areaInfu);
    
            return tree;
    
        }

### 4.Service ###

public List<AreaInfo> selectAll();

### 5.serviceimpl ###

@Override
        public List<AreaInfo> selectAll() {
        
            return pasCaseMapper.selectAll();
        }

### 6.Mapper ###

List<AreaInfo> selectAll();

### 7.MapperXML ###

<select id="selectAll" resultType="com.zhecre.jx.business.model.cases.response.AreaInfo">
            SELECT INDEXID,INDEXNAME,PARENTID,UNIT,COEF FROM PAS_INDEX  WHERE INDEXID LIKE 'IA%'
        </select>

### 8.工具类： ###

package com.zhecre.jx.business.common;
    
    import cn.hutool.core.collection.CollectionUtil;
    import lombok.extern.slf4j.Slf4j;
    import org.springframework.util.CollectionUtils;
    
    import java.util.*;
    import java.util.stream.Collectors;
    
    
    @Slf4j
    public class TreeUtil {
        
    
    
    
        //java8构建树
    
        /**
         * 将平铺的List<T>转换成Tree
         * @param listNodes
         * @param <T>
         * @return
         */
        public static <T extends BaseTreeNode> List<T> getTree(List<T> listNodes){
        
    //        判断当前listNodes 是否为空
            if (CollectionUtil.isNotEmpty(listNodes)){
        
                //根据pid分组 key 都是parentId ,value 所有的permission对象
                Map<String, List<T>> listMap = listNodes.stream().collect(Collectors.groupingBy(t -> Optional.ofNullable(t.getParentid()).orElse(String.valueOf("root"))));
                //得到一级分类,第一级pid==0
    
                List<T> oneLevelClassify = listMap.get("root");//最底层跟节点id
                //递归
                List<T> list = getChildList(oneLevelClassify, listMap);
                return list;
            }
            return new ArrayList<>();
        }
    
        /**
         * 获取子节点
         * @param classifies
         * @param groupMap
         * @param <T>
         * @return
         */
        private static <T extends BaseTreeNode> List<T> getChildList(List<T> classifies, Map<String, List<T>> groupMap) {
        
            //判断一级的数据是否为空
           if (CollectionUtil.isNotEmpty(classifies)){
        
               //遍历 tree 父级对象
               for (T tree:classifies){
        
                   //所有的二级的list对象
                   List<T> classifyList = groupMap.get(tree.getIndexid());
                   //判断是否为空
                   if (!CollectionUtils.isEmpty(classifyList)) {
        
                       tree.setChildren((List<BaseTreeNode>)classifyList);
                       getChildList(classifyList, groupMap);
                   } else {
        
                       tree.setChildren(null);
                   }
               }
               //循环遍历
    //           classifies.forEach(tree -> {
        
    //               List<T> classifyList = groupMap.get(tree.getId());
    //               if (!CollectionUtils.isEmpty(classifyList)) {
        
    //                   tree.setChildren((List<BaseTreeNode>)classifyList);
    //                   getChildList(classifyList, groupMap);
    //               } else {
        
    //                   tree.setChildren(null);
    //               }
    //           });
               return classifies;
           }
           return new ArrayList<>();
        }
    }