本文实例为大家分享了java实现省市区转换成树形结构的具体代码，供大家参考，具体内容如下

前言： 为什我想写这篇博客呢？第一方面是记录，另一方面是分享。

1. 创建数据库表

CREATE TABLE `area`  (
  `AREA_CODE` varchar(16) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '区域ID',
  `AREA_NAME` varchar(512) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '区域名称',
  `SUPERIOR_CODE` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '父级代码',
  `AREA_LEVEL` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '级别',
  `AREA_SORT` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '排序',
  `REMARK` varchar(100) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '备注',
  `DELETE_FLAG` varchar(1) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '删除标识',
  `CREATED_BY` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '创建人',
  `CREATION_TIME` timestamp(0) NOT NULL DEFAULT CURRENT_TIMESTAMP(0) ON UPDATE CURRENT_TIMESTAMP(0) COMMENT '创建时间',
  `UPDATED_BY` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '更新人',
  `UPDATE_TIME` timestamp(0) NOT NULL DEFAULT '2020-01-01 00:00:00' COMMENT '更新时间',
  PRIMARY KEY (`AREA_CODE`) USING BTREE,
  UNIQUE INDEX `UK_T_PUB_AREA_AREA_CODE`(`AREA_CODE`) USING BTREE,
  INDEX `IDX_T_PUB_AREA_AREA_LEVEL`(`AREA_LEVEL`) USING BTREE,
  INDEX `IDX_T_PUB_AREA_SUPERIOR_CODE`(`SUPERIOR_CODE`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci COMMENT = '区域表' ROW_FORMAT = DYNAMIC;
 
SET FOREIGN_KEY_CHECKS = 1;

2. 创建java实体

@Data
public class Area {
    //区域ID
    private String areaCode;
    //区域名称
    private String areaName;
    //父级代码
    private String superiorCode;
    //级别
    private String areaLevel;
    //排序
    private String areaSort;
    //备注
    private String remark;
    //删除标识
    private String deleteFlag;
    //创建人
    private String createdBy;
    //创建时间
    private Date creationTime;
    //更新人
    private String updatedBy;
    //更新时间
    private Date updateTime;
 
}

3. 创建mapper

public interface AreaMapper {
    int deleteByPrimaryKey(String areaCode);
 
    int insert(Area record);
 
    int insertSelective(Area record);
 
    Area selectByPrimaryKey(String areaCode);
 
    int updateByPrimaryKeySelective(Area record);
 
    int updateByPrimaryKey(Area record);
    List<Area> queryAreaAll();
    List<Map<String, String>> queryMap();
}

4. 创建service

@Service
public class AreaService {
    @Autowired
    private AreaMapper areaMapper;
    //修建
   public String queryArea(){
       List<Area> mapList = areaMapper.queryAreaAll();
       JSONArray result = ListToTree.buildTree(JSONArray.parseArray(JSON.toJSONString(mapList)),"areaCode","superiorCode","children");
       return result.toJSONString();
   }    //修建
   public String queryAreaCode(){
       List<Map<String, String>> mapList = areaMapper.queryMap();
       JSONArray result = ListToTree.buildTree(JSONArray.parseArray(JSON.toJSONString(mapList)),"value","superiorCode","children");
       return result.toJSONString();
   }
}

5. 转换成树形结构的工具类

public class ListToTree {
    public static JSONArray buildTree(JSONArray arr, String id, String pid, String Chirden) {
        //新建一个JSONArray来接收组装成树形结构的返回值
        JSONArray jsonArray = new JSONArray();
        //新建一个JSONObject对象
        JSONObject hash = new JSONObject();
        //将数组转换为object格式
        for (int i = 0; i < arr.size(); i++) {
            //获取当前的JSON对象
            JSONObject json = (JSONObject) arr.get(i);
            //把当前id作为键，当前JSON对象作为值 put回hash这个Object对象中
            //这里的put方法类似于map的put方法
            hash.put(json.getString(id), json);
        }
        //遍历结果集
        for (int j = 0; j < arr.size(); j++) {
            //单条记录
            JSONObject aVal = (JSONObject) arr.get(j);
            //在hash中取出key为单条记录中pid的值
            String pidStr = "";
            //如果父级id不等于null
            if (aVal.get(pid) != null) {
                pidStr = aVal.get(pid).toString();
            }
            //从hash这个对象中获取父级对象  parent
            JSONObject hashParent = (JSONObject) hash.get(pidStr);
            //如果记录的pid存在，则说明它有父节点，将她添加到孩子节点的集合中
            if (hashParent != null) {
                //检查是否有child属性
                if (hashParent.get(Chirden) != null) {
                    //有子节点 则先将子节点取出
                    JSONArray children = (JSONArray) hashParent.get(Chirden);
                    //然后把当前这个对象放进子节点之中
                    children.add(aVal);
                    //最后把子节点在放回父节点之中
                    hashParent.put(Chirden, children);
                } else {
                    //无子节点 则新建一个子节点
                    JSONArray children = new JSONArray();
                    //然后再把当前对象放进去
                    children.add(aVal);
                    //最后在放回父节点之中
                    hashParent.put(Chirden, children);
                }
            } else {
                jsonArray.add(aVal);
            }
        }
        return jsonArray;
 
    }
}

6. 创建controller

@RestController
public class AreaController {
    @Resource
    private AreaService areaService;
 
    @RequestMapping(value = "/area",method = RequestMethod.POST)
    public String queryArea() {
        return areaService.queryArea();
    }
    @RequestMapping(value = "/area1",method = RequestMethod.POST)
    public String queryAreaDemo() {
        return areaService.queryAreaCode();
    }
}

7. 接口测试

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