list 和 collection匹配
2022-05-19 接手项目以来遇到过许多问题，今天聊一下mybatis collection
collection 作为集合操作的一定要使用List来对应接收数据。以下是使用。
首先配置好mybatis的jar和数据库驱动，web等
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.2.2</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
接下来编写实体类 Company 和 WebData
@Data
public class Company {
private String companyId;
private String companyName;
private List<WebData> or; // 这里一定要用List
}
@Data
public class WebData {
private Integer id;
private String assc;
}
实体类关系or 用List去承接数据库返回的数据，一定要用List。set不可以，
编写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="org.danyuan.application.dao.WebDao">
<resultMap id="baseCompanyMap" type="org.danyuan.application.po.Company">
<id column="company_id" property="companyId"/>
<result column="company_name" property="companyName"/>
<collection property="or" ofType="org.danyuan.application.po.WebData">
<id column="id" property="id"/>
<result column="assc" property="assc"/>
</collection>
</resultMap>
<select id="findAll" parameterType="java.lang.String" resultMap="baseCompanyMap">
SELECT
company_id ,
company_name,
id,
assc
FROM application.test_collection
WHERE company_id IN
<foreach collection="ids" item="idItem" open="(" close=")" separator="," index="idIndex">
${idItem}
</foreach>
</select>
</mapper>
这里我用一张表测试的，实际上使用collection 的情况绝大的概率是关联了子表的，这里面主要注意使用resultMap 的写法，返回结果会自动进行数据合并company_id相同的数据，id不同的添加到list中下面是我的测试数据
image.png
编写测试Service方法 然后提供一个web接口查看返回值
public List<Company> test() {
logger.info("开始测试");
List<Company> list = webDao.findAll(new String[] { "123456", "444" });
logger.info("测试 list size= {}", list.size());
list.forEach(aa -> {
logger.info("测试 web.size={} aa= {}", aa.getOr().size(), aa.toString());
});
logger.info("测试结束");
return list;
}接口返回
image.png
控制台打印
2022-05-20 11:11:02.378 INFO 7176 --- [p-nio-80-exec-1] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2022-05-20 11:11:02.524 INFO 7176 --- [p-nio-80-exec-1] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
JDBC Connection [HikariProxyConnection@1380765898 wrapping com.mysql.cj.jdbc.ConnectionImpl@22eec6e4] will not be managed by Spring
==> Preparing: SELECT company_id , company_name, id, assc FROM application.test_collection WHERE company_id IN ( 123456 , 444 )
==> Parameters:
<== Columns: company_id, company_name, id, assc
<== Row: 123456, aaa, 1, ssss
<== Row: 123456, aaa, 2, 4444
<== Row: 123456, aaa, 3, 456789
<== Row: 123456, aaa, 4, 444445w
<== Row: 444, 44, 5, 56
<== Row: 444, 54, 6, 55
<== Total: 6
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@2cc4c8e4]
2022-05-20 11:11:02.579 INFO 7176 --- [p-nio-80-exec-1] o.d.application.service.CompanyService : 测试 list size= 2
2022-05-20 11:11:02.580 INFO 7176 --- [p-nio-80-exec-1] o.d.application.service.CompanyService : 测试 web.size=4 aa= Company(companyId=123456, companyName=aaa, or=[WebData(id=1, assc=ssss), WebData(id=2, assc=4444), WebData(id=3, assc=456789), WebData(id=4, assc=444445w)])
2022-05-20 11:11:02.580 INFO 7176 --- [p-nio-80-exec-1] o.d.application.service.CompanyService : 测试 web.size=2 aa= Company(companyId=444, companyName=44, or=[WebData(id=5, assc=56), WebData(id=6, assc=55)])
2022-05-20 11:11:02.580 INFO 7176 --- [p-nio-80-exec-1] o.d.application.service.CompanyService : 测试结束
