通过代码加载mybatis的mapper xml-编程知识

通过代码加载mybatis的mapper xml

jpa 性能确实差，转战 mybatis 了

依赖

        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.15</version></dependency><!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.33</version></dependency><!-- https://mvnrepository.com/artifact/com.zaxxer/HikariCP --><dependency><groupId>com.zaxxer</groupId><artifactId>HikariCP</artifactId><version>4.0.3</version></dependency><!-- https://mvnrepository.com/artifact/org.projectlombok/lombok --><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.30</version><scope>provided</scope></dependency>

实体 UserEntity

@Data
public class UserEntity {private Long id;private String username;private String password;private String nickname;private Date createTime;private Date updateTime;
}

mapper接口 UserMapper

public interface UserMapper {List<UserEntity> selectAll();
}

xml mapper/UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="top.lingkang.mmt.mapper.UserMapper"><select id="selectAll" resultType="top.lingkang.mmt.entity.UserEntity">select * from t_user</select>
</mapper>

加载调用

import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariDataSource;
import org.apache.ibatis.builder.xml.XMLMapperBuilder;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.apache.ibatis.transaction.TransactionFactory;
import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;
import top.lingkang.mmt.mapper.UserMapper;import java.io.InputStream;/*** @author lingkang* Created by 2024/2/28*/
public class Demo01 {public static void main(String[] args) throws Exception {HikariConfig config = new HikariConfig();config.setJdbcUrl("jdbc:mysql://localhost:3306/test?useSSL=true&serverTimezone=UTC");config.setUsername("root");config.setPassword("123456");HikariDataSource dataSource = new HikariDataSource(config);Configuration configuration = new Configuration();// 用for循环加载所有 xmlInputStream inputStream = Resources.getResourceAsStream("mapper/UserMapper.xml");XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, "mapper/UserMapper.xml",configuration.getSqlFragments());mapperParser.parse();// 配置TransactionFactory transactionFactory = new JdbcTransactionFactory();Environment environment = new Environment("dev", transactionFactory, dataSource);configuration.setEnvironment(environment);configuration.setMapUnderscoreToCamelCase(true);// 下划线转化驼峰SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);// 查询SqlSession session = sqlSessionFactory.openSession();UserMapper mapper = session.getMapper(UserMapper.class);System.out.println(mapper.selectAll());// 查询所有session.close();}
}