背景
实际开发过程中经常需要查询节点树,根据指定节点获取子节点列表,以下记录了获取节点树的操作,以备不时之需。
使用场景
可以用于系统部门组织机构、商品分类、城市关系等带有层级关系的数据结构；
设计思路
递归模型
即根节点、枝干节点、叶子节点，数据模型如下：
| id | code | name | parent_code |
|---|---|---|---|
| 1 | 10000 | 电脑 | 0 |
| 2 | 20000 | 手机 | 0 |
| 3 | 10001 | 联想笔记本 | 10000 |
| 4 | 10002 | 惠普笔记本 | 10000 |
| 5 | 1000101 | 联想拯救者 | 10001 |
| 6 | 1000102 | 联想小新系列 | 10001 |
实现代码
表结构
CREATE TABLE `tree_table` (
`id` int NOT NULL AUTO_INCREMENT COMMENT '主键ID',
`code` varchar(10) NOT NULL COMMENT '编码',
`name` varchar(20) NOT NULL COMMENT '名称',
`parent_code` varchar(10) NOT NULL COMMENT '父级编码',
PRIMARY KEY (`id`) USING BTREE
) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC COMMENT='树形结构测试表';表数据
INSERT INTO `tree_table`(`code`, `name`, `parent_code`) VALUES ('10000', '电脑', '0');
INSERT INTO `tree_table`(`code`, `name`, `parent_code`) VALUES ('10001', '联想笔记本', '10000');
INSERT INTO `tree_table`(`code`, `name`, `parent_code`) VALUES ('10002', '惠普笔记本', '10000');
INSERT INTO `tree_table`(`code`, `name`, `parent_code`) VALUES ('1000101', '联想拯救者', '10001');
INSERT INTO `tree_table`(`code`, `name`, `parent_code`) VALUES ('1000102', '联想小新系列', '10001');
实体
@Data
@TableName("tree_table")
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
public class TreeTable {
@TableId(type = IdType.AUTO)
private Integer id;
private String code;
private String name;
private String parentCode;
@TableField(exist = false)
private List<TreeTable> childNode;
}
mybatis
mapper
public interface TreeTableMapper extends BaseMapper<TreeTable> {
public List<TreeTable> noteTree();
}
xml
<?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.springboot.example.mysqltree.mapper.TreeTableMapper">
<resultMap id="BaseResultMap" type="com.springboot.example.mysqltree.model.entity.TreeTable">
<result column="id" property="id"/>
<result column="code" property="code"/>
<result column="name" property="name"/>
<result column="parent_code" property="parentCode"/>
</resultMap>
<resultMap id="NodeTreeResult" type="com.springboot.example.mysqltree.model.entity.TreeTable"
extends="BaseResultMap">
<collection property="childNode" column="code" ofType="com.springboot.example.mysqltree.model.entity.TreeTable"
javaType="java.util.ArrayList" select="nextNoteTree">
</collection>
</resultMap>
<sql id="Base_Column_List">
id,
code,
`name`,
parent_code
</sql>
<select id="nextNoteTree" resultMap="NodeTreeResult">
select
<include refid="Base_Column_List"/>
from tree_table
where parent_code=#[code]
</select>
<select id="noteTree" resultMap="NodeTreeResult">
select
<include refid="Base_Column_List"/>
from tree_table
where parent_code='0'
</select>
</mapper>
- noteTree ：获取所有父级节点数据；
- nextNoteTree：循环获取子节点数据，知道叶子节点结束；
- column：关联表的列名；
- ofType：返回类型
启动类
@Slf4j
@Component
public class TreeTableCommandLineRunner implements CommandLineRunner {
@Resource
private TreeTableMapper treeTableMapper;
@Override
public void run(String... args) throws Exception {
log.info(JSONUtil.toJsonPrettyStr(treeTableMapper.noteTree()));
}
}
最终效果
[
{
"code": "10000",
"childNode": [
{
"code": "10001",
"childNode": [
{
"code": "1000101",
"childNode": [
],
"parentCode": "10001",
"name": "联想拯救者",
"id": 5
},
{
"code": "1000102",
"childNode": [
],
"parentCode": "10001",
"name": "联想小新系列",
"id": 6
}
],
"parentCode": "10000",
"name": "联想笔记本",
"id": 3
},
{
"code": "10002",
"childNode": [
],
"parentCode": "10000",
"name": "惠普笔记本",
"id": 4
}
],
"parentCode": "0",
"name": "电脑",
"id": 1
}
]
注意事项
使用mybatis时如加载不到mapper xml需在pom.xml添加以下配置：
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
总结
使用递归方式是比较常见的方式，优点是实现简单，直观的体现层级关系，但是数据量大的情况下效率会略低；欢迎使用其他方式的小伙伴分享自己的实现思路。
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