java实现多层级目录树详解
二，建表建库
在建表时，需要注意的是一定要一个Pid和当前id，这样用于实现这个子级和父级的关联。建表语句如下
CREATE TABLE `site` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `pid` bigint(20) DEFAULT NULL COMMENT '父id', `p_name` varchar(50) DEFAULT NULL COMMENT '父名称', `current_name` varchar(50) DEFAULT NULL COMMENT '当前层级名称', `created_time` datetime DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP COMMENT '创建时间', `updated_time` datetime DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间', `is_deleted` tinyint(4) DEFAULT NULL COMMENT '是否删除', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=35 DEFAULT CHARSET=utf8;
可以参考一下我的，也可以自己插入一些数据。接下来插入数据
insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (0,'顶级','江西',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (0,'顶级','广东',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (0,'顶级','湖南',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (0,'顶级','河北',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (1,'江西','南昌',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (1,'江西','赣州',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (1,'江西','九江',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (1,'江西','佛山',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (2,'广东','广州',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (2,'广东','深圳',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (2,'广东','佛山',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (2,'广东','东莞',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (3,'湖南','长沙',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (3,'湖南','湘潭',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (3,'湖南','岳阳',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (4,'河北','唐山',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (4,'河北','石家庄',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (4,'河北','保定',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (10,'深圳',,'南山',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (10,'深圳',,'福田',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (10,'深圳',,'宝安',,now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (10,'深圳',,'龙岗',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (10,'深圳',,'龙华',now(),now(),0); insert into site (pid,p_name,current_name,created_time,updated_time,is_deleted) VALUES (10,'深圳',,'光明',now(),now(),0);
1，实体类
/** * @author zhenghuisheng * @date : 2022/10/8 */ @Data @AllArgsConstructor @NoArgsConstructor public class Site implements Serializable { @TableId(value = "id", type = IdType.ASSIGN_ID) @JsonSerialize(using = ToStringSerializer.class) public Long id; @JsonSerialize(using = ToStringSerializer.class) public Long pid; public String pname; public String currentName; public Date createdTime; public Date updatedTime; public Integer isDeleted; }
2、dto类
对应上面的实体类，并在里面加入一个siteDtoList字段，用于保存当前结点的子集。
@Data public class SiteDto implements Serializable { private static final long serialVersionUID = 1L; //用户id public Long id; //父id public Long pid; //父级name public String pname; //当前名称 public String currentName; //创建时间 public String createdTime; //更新时间 public String updatedTime; //是否删除 public Integer isDeleted; //子集,用于存储当前目录下面的全部子集 public List<SiteDto> siteDtoList; }
3，mybatis里面的sql
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.example.demo.mapper.SiteMapper"> <resultMap id="baseMap" type="com.example.demo.pojo.Site"> <id column="id" property="id"></id> <result column="pid" property="pid"></result> <result column="p_name" property="pname"></result> <result column="current_name" property="currentName"></result> <result column="created_time" property="createdTime"></result> <result column="updated_time" property="updatedTime"></result> <result column="is_deleted" property="isDeleted"></result> </resultMap> <select id="queryAll" resultMap="baseMap" resultType="com.example.demo.pojo.Site"> select * from site where is_deleted = 0; </select> </mapper>
4，Mapper类
/** * @author zhenghuisheng * @date : 2022/10/8 */ @Repository @Mapper public interface SiteMapper { List<Site> queryAll(); }
5,service类
把这个看懂就基本上没问题了
/** * @author zhenghuisheng * @date : 2022/10/8 */ @Service public class SiteService { @Autowired private SiteMapper siteMapper; public List<SiteDto> queryAll(){ List<SiteDto> datas = new ArrayList<>(); //获取全部数据 List<Site> siteList = siteMapper.queryAll(); if (siteList != null){ //将这个数据赋值到dto里面 List<SiteDto> siteDtoList = siteList.stream().map(site -> { SiteDto siteDto = new SiteDto(); BeanUtils.copyProperties(site,siteDto); //时间格式化 siteDto.setCreatedTime(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(site.createdTime)); siteDto.setUpdatedTime(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(site.updatedTime)); return siteDto; }).collect(Collectors.toList()); //遍历全部的数据，利用递归思想，获取全部的子集 siteDtoList.forEach(e ->{ //判断当前id是否为其他数据的父id List<SiteDto> childrenList = getChildrenList(e.getId(), siteDtoList); //设置子集,如果到了最后一级，那么直接设置为null，不展示这个属性即可 e.setSiteDtoList(childrenList != null ? childrenList : null); }); //获取所有的顶点数据，即最上层数据,该数据的pid为0 //注意这个pid的数据类型，如果数据库为varchar则equals("0") 整型则为equals(0) List<SiteDto> siteDtoParents = siteDtoList.stream().filter(t -> t.getPid().equals(0L)).collect(Collectors.toList()); datas.addAll(siteDtoParents); } return datas; } //获取全部的子集合 public static List<SiteDto> getChildrenList(String id,List<SiteDto> list){ //便利全部数据，将需要的数据过滤出来 return list.stream().filter(t-> t.getPid().equals(id)).collect(Collectors.toList()); } }
7，Contrller类测试
/** * @author zhenghuisheng * @date : 2022/10/8 */ @RestController public class SiteController { @Autowired private SiteService siteService; @RequestMapping("/getAllData") public List<SiteDto> getAllData(){ return siteService.queryAll(); } }
故乡明
