通过代码加载mybatis的mapper xml

jpa 性能确实差，转战 mybatis 了

依赖

xml 复制代码

        <!-- 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

java 复制代码

@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

java 复制代码

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

xml mapper/UserMapper.xml

xml 复制代码

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//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

java 复制代码

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 xml

        InputStream 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();
    }
}

结果截图

转自：https://lingkang.top/archives/tong-guo-dai-ma-jia-zai-mybatis-de-mapperxml