java树形加工

川长思鸟来 2024-04-17 17:56 63阅读 0赞

当需要树形结构时，可以考虑一次性把树从sql查出，通过加工得到。  
实现类代码

package com.jp.demo.service.impl;
    
    import com.jp.demo.dao.mapper.RegionMapper;
    import com.jp.demo.pojo.vo.RegionVO;
    import com.jp.demo.service.RegionService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    import org.springframework.util.CollectionUtils;
    
    import java.util.*;
    
    
    @Service
    public class RegionServiceImpl implements RegionService {
    
        @Autowired
        private RegionMapper regionMapper;
    
        @Override
        public List<RegionVO> getRegionTree() {
            List<RegionVO> list = createTree(regionMapper.getRegionInfo());
            return list;
        }
    
        private List<RegionVO> createTree(List<RegionVO> list) {
            if (CollectionUtils.isEmpty(list)) {
                return Collections.emptyList();
            } else {
                Map<String, RegionVO> map = new LinkedHashMap<>();
                list.stream().forEach((regionVO) -> {
                    map.put(String.valueOf(regionVO.getItemId()), regionVO);
                });
                List<RegionVO> treeResult = new LinkedList<>();
                Iterator item = map.values().iterator();
                while (item.hasNext()) {
                    RegionVO regionVO = (RegionVO) item.next();
                    if (0 == regionVO.getFatherId()) {
                        treeResult.add(regionVO);
                    } else {
                        String parentId = String.valueOf(regionVO.getFatherId());
                        RegionVO child = map.get(parentId);
                        if (child != null) {
                            child.addChild(regionVO);
                        }
                    }
                }
                return treeResult;
            }
        }
    
    }

实体

package com.jp.demo.pojo.vo;
    
    import lombok.Data;
    
    import java.util.ArrayList;
    import java.util.List;
    
    
    @Data
    public class RegionVO {
    
        //id
        private Integer itemId;
    
        //名称
        private String itemName;
    
        //父id
        private Integer fatherId;
    
        //级别
        private Integer level;
    
        //子节点信息
        private List<RegionVO> children;
    
    
        public void addChild(RegionVO child) {
            if (this.children == null) {
                this.children = new ArrayList<>();
            }
            this.children.add(child);
        }
    
    }