Java接口返回省市区树形结构的实现

CREATE TABLE `sys_region`  (
  `id` int(19) NOT NULL AUTO_INCREMENT COMMENT 'id',
  `pid` int(19) NULL DEFAULT NULL COMMENT '上级ID，一级为0',
  `name` varchar(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '名称',
  `tree_level` int(3) NULL DEFAULT NULL COMMENT '层级',
  `leaf` int(3) NULL DEFAULT NULL COMMENT '是否叶子节点  0：否   1：是',
  `sort` int(19) NULL DEFAULT NULL COMMENT '排序',
  `create_by` varchar(19) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '创建者',
  `create_time` datetime(0) NULL DEFAULT NULL COMMENT '创建时间',
  `update_by` varchar(19) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL COMMENT '更新者',
  `update_time` datetime(0) NULL DEFAULT NULL COMMENT '更新时间',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 820202 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci COMMENT = '行政区域' ROW_FORMAT = Dynamic;

package org.jeecg.modules.entity;

import java.io.Serializable;
import java.io.UnsupportedEncodingException;
import java.util.Date;
import java.math.BigDecimal;
import java.util.List;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;
import com.fasterxml.jackson.annotation.JsonFormat;
import org.springframework.format.annotation.DateTimeFormat;
import org.jeecgframework.poi.excel.annotation.Excel;
import org.jeecg.common.aspect.annotation.Dict;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import lombok.EqualsAndHashCode;
import lombok.experimental.Accessors;

/**
 * @Description: 行政区域实体
 * @Author:wyh
 * @Date: 2021-04-06
 */
@Data
@TableName("sys_region")
@Accessors(chain = true)
@EqualsAndHashCode(callSuper = false)
@ApiModel(value = "sys_region对象", description = "行政区域")
public class SysRegion implements Serializable {
    private static final long serialVersionUID = 1L;

    /**
     * id
     */
    @TableId(type = IdType.ASSIGN_ID)
    @ApiModelProperty(value = "id")
    private Integer id;
    /**
     * 上级ID，一级为0
     */
    @Excel(name = "上级ID，一级为0", width = 15)
    @ApiModelProperty(value = "上级ID，一级为0")
    private Integer pid;
    /**
     * 名称
     */
    @Excel(name = "名称", width = 15)
    @ApiModelProperty(value = "名称")
    private String name;
    /**
     * 层级
     */
    @Excel(name = "层级", width = 15)
    @ApiModelProperty(value = "层级")
    private Integer treeLevel;
    /**
     * 是否叶子节点  0：否   1：是
     */
    @Excel(name = "是否叶子节点  0：否   1：是", width = 15)
    @ApiModelProperty(value = "是否叶子节点  0：否   1：是")
    private Integer leaf;
    /**
     * 排序
     */
    @Excel(name = "排序", width = 15)
    @ApiModelProperty(value = "排序")
    private Integer sort;
    /**
     * 创建者
     */
    @ApiModelProperty(value = "创建者")
    private String createBy;
    /**
     * 创建时间
     */
    @JsonFormat(timezone = "GMT+8", pattern = "yyyy-MM-dd")
    @DateTimeFormat(pattern = "yyyy-MM-dd")
    @ApiModelProperty(value = "创建时间")
    private Date createTime;
    /**
     * 更新者
     */
    @ApiModelProperty(value = "更新者")
    private String updateBy;
    /**
     * 更新时间
     */
    @JsonFormat(timezone = "GMT+8", pattern = "yyyy-MM-dd")
    @DateTimeFormat(pattern = "yyyy-MM-dd")
    @ApiModelProperty(value = "更新时间")
    private Date updateTime;
    /**
     * 子列表
     */
    @TableField(exist = false)  //表示这个属性不属于表中的字段
    private List<SysRegion> childList;

}

    /**
     * @Author wyh
     * @Description  查询所有省级区域以树形式展示关系
     * @Date 10:00 2022/12/27
    **/
    List<SysRegion> queryAllProvinceTree();

  @Override
    public List<SysRegion> queryAllProvinceTree() {
        // 获取全部区域
        List<SysRegion> list = this.query().list();
        // 省区域
        List<SysRegion> provinceListOneLevelRegion = list.stream().filter(item -> item.getPid().intValue()==0).collect(Collectors.toList());
        //遍历一级地区
        provinceListOneLevelRegion.stream().forEach(oneItem ->
                {
                    //获得二级
                    List<SysRegion> twoLevelRegion = list.stream().filter(twoItem -> twoItem.getPid().intValue() == oneItem.getId().intValue())
                            .collect(Collectors.toList());
                    //遍历二级
                    twoLevelRegion.stream().forEach(twoItem ->
                    {
                        //获得三级
                        List<SysRegion> threeLevelRegion = list.stream().filter(threeItem -> threeItem.getPid().intValue() == twoItem.getId().intValue())
                                .collect(Collectors.toList());
                        twoItem.setChildList(threeLevelRegion);
                    });
                    oneItem.setChildList(twoLevelRegion);
                }
        );
        // 最终的树形结构列表
        return provinceListOneLevelRegion;
    }

 /**
     * 查询所有省级区域以树形式展示关系
     *
     * @return
     */
    @ApiOperation(value = "行政区域-查询所有省级区域以树形式展示关系", notes = "行政区域-查询所有省级区域以树形式展示关系")
    @GetMapping(value = "/queryAllProvinceTree")
    public Result<?> queryAllProvinceTree() {
        return Result.OK(SysRegionService.queryAllProvinceTree());
    }