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：
| 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
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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
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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
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@Data @TableName ( "tree_table" ) @EqualsAndHashCode (callSuper = false ) @Accessors (chain = true ) public class TreeTable { /** * 主键ID */ @TableId (type = IdType.AUTO) private Integer id; /** * 编码 */ private String code; /** * 名称 */ private String name; /** * 父级编码 */ private String parentCode; /** * 子节点 */ @TableField (exist = false ) private List<TreeTable> childNode; } |
mybatis
mapper
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public interface TreeTableMapper extends BaseMapper<TreeTable> { /** * 获取树形结构数据 * * @return 树形结构 */ public List<TreeTable> noteTree(); } |
xml
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<? 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
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@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
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[ { "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：
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< 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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原文链接：https://juejin.cn/post/6987283625511223304
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