某天，产品经理给了这么一个需求技术小哥，能不能帮用户添加一个搜索栏，查询包含某个关键字的所有类目。技术小哥稍微想了一下，目前跟类目相关的表有两个，一个是content_category类目表，一个是content_system内容系统表。而用户要查找的关键字是存在content_system表里面，这样一来需要连表查询一下。难度好像不大，也就爽快地答应了。
技术小哥再仔细分析了一下两个表的结构：
CREATE TABLE `content_category` (
`category_id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT '类目编号Id',
`pid` int(10) unsigned DEFAULT NULL COMMENT '上级编号id',
`level` tinyint(4) NOT NULL COMMENT '层级',
`name` varchar(20) NOT NULL COMMENT '名称',
`description` varchar(200) DEFAULT NULL COMMENT '描述',
`icon` varchar(50) DEFAULT NULL COMMENT '图标',
`type` tinyint(3) NOT NULL DEFAULT '1' COMMENT '类型(1:普通,2:热门...)',
`alias` varchar(20) DEFAULT NULL COMMENT '别名',
`system_id` int(11) DEFAULT NULL COMMENT '系统编号id',
`ctime` bigint(20) unsigned NOT NULL COMMENT '创建时间',
`orders` bigint(255) unsigned NOT NULL COMMENT '排序',
`attention` bigint(20) unsigned NOT NULL COMMENT '关注度',
PRIMARY KEY (`category_id`),
KEY `content_category_orders` (`orders`),
KEY `content_category_pid` (`pid`),
KEY `content_category_alias` (`alias`),
KEY `content_category_level` (`level`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COMMENT='内容类目表';
CREATE TABLE `content_system` (
`system_id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT '系统编号id',
`name` varchar(20) NOT NULL COMMENT '系统名称',
`code` varchar(20) DEFAULT NULL COMMENT '别名',
`description` varchar(300) DEFAULT NULL COMMENT '描述',
`ctime` bigint(20) DEFAULT NULL COMMENT '创建时间',
`orders` bigint(20) DEFAULT NULL COMMENT '排序',
PRIMARY KEY (`system_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8mb4 COMMENT='内容系统表';
不难看出，两个表都有system_id作为关联，当用户输入一个关键字，例如 code = "news" 时候，系统需要自动搜索出 system_id = 1 的所有类目信息。
于是技术小哥开始了他的工作，首先是定义Mapper.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.thomson.content.rpc.mapper.ContentCategoryExtMapper">
<!-- 定义基础类型 -->
<resultMap id="BaseResultMap" type="com.thomson.content.dao.model.ContentCategory">
<!-- 实体类的字段名和数据表的字段名映射 -->
<id column="category_id" jdbcType="INTEGER" property="categoryId" />
<result column="pid" jdbcType="INTEGER" property="pid" />
<result column="level" jdbcType="TINYINT" property="level" />
<result column="name" jdbcType="VARCHAR" property="name" />
<result column="description" jdbcType="VARCHAR" property="description" />
<result column="icon" jdbcType="VARCHAR" property="icon" />
<result column="type" jdbcType="TINYINT" property="type" />
<result column="alias" jdbcType="VARCHAR" property="alias" />
<result column="system_id" jdbcType="INTEGER" property="systemId" />
<result column="ctime" jdbcType="BIGINT" property="ctime" />
<result column="orders" jdbcType="BIGINT" property="orders" />
<result column="attention" jdbcType="BIGINT" property="attention" />
</resultMap>
<!--继承基础类型BaseResultMap， association 一对一关联查询 -->
<resultMap extends="BaseResultMap" id="ClassesResultMap" type="com.thomson.content.dao.model.ContentCategory">
</resultMap> <!-- 这一步是关键的连表查询 -->
<select id="selectContentCategoryByCode" parameterType="map" resultMap="ClassesResultMap">
select content_c.* from content_category content_c left join content_system content_s on content_s.code=content_s.code=#{code,jdbcType=VARCHAR}
where content_s.system_id=content_c.system_id
</select>
<!-- 缓存 -->
<cache type="org.mybatis.caches.ehcache.LoggingEhcache" />
</mapper>
然后是Mapper接口
package com.thomson.content.rpc.mapper;
import com.thomson.content.dao.model.ContentCategory;
import org.apache.ibatis.annotations.Param;
import java.util.List;
/**
* 类目ExtMapper
* Created by Thomson on 2022/01/10.
* 根据content_system 的 code 获取类目
*/
public interface ContentCategoryExtMapper {
int up(String code);
int down(String code);
List<ContentCategory> selectContentCategoryByCode(@Param("code") String code);
}
接下来是实现类
import com.thomson.Content.dao.model.ContentArticle;
import com.thomson.Content.rpc.mapper.ContentCategoryExtMapper;
import com.thomson.common.annotation.BaseService;
import com.thomson.common.base.BaseServiceImpl;
import com.thomson.Content.dao.mapper.ContentCategoryMapper;
import com.thomson.Content.dao.model.ContentCategory;
import com.thomson.Content.dao.model.ContentCategoryExample;
import com.thomson.Content.rpc.api.ContentCategoryService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;
/**
* ContentCategoryService实现
* Created by Thomson on 2021/01/10.
*/
@Service
@Transactional
@BaseService
public class ContentCategoryServiceImpl extends BaseServiceImpl<ContentCategoryMapper, ContentCategory, ContentCategoryExample> implements ContentCategoryService {
private static final Logger LOGGER = LoggerFactory.getLogger(ContentCategoryServiceImpl.class);
@Autowired
ContentCategoryExtMapper ContentCategoryExtMapper;
// @Override
public List<ContentCategory> selectContentCategoryByCode(String code) {
return ContentCategoryExtMapper.selectContentCategoryByCode(code);
}
}
在controll下获取数据
@ApiOperation(value = "类目列表")
@RequiresPermissions("content:category:read")
@RequestMapping(value = "/list", method = RequestMethod.GET)
@ResponseBody
public Object list(
@RequestParam(required = false, defaultValue = "0", value = "offset") int offset,
@RequestParam(required = false, defaultValue = "10", value = "limit") int limit,
@RequestParam(required = false, value = "sort") String sort,
@RequestParam(required = false, value = "order") String order) {
Map<String, Object> result = new HashMap<>(2);
String code = "news";
List<ContentCategory> categories = ContentCategoryService.selectContentCategoryByCode(code);
System.out.print("\n"+categories+"\n");
result.put("rows", categories); result.put("total", total);
return result;
}
至此，技术小哥获取到了自己想要的数据。顺利完成了产品经理给的任务。
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