一小时迅速入门Mybatis之初识篇

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>Mybatis-Test</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <!-- 引入Mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <!-- mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>

    </dependencies>

</project>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&amp;characterEncoding=utf-8&amp;useSSL=false&amp;serverTimezone=GMT%2B8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="TestMapper.xml"/>
    </mappers>
</configuration>

<?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="TestMapper">
    <select id="list" resultType="map">
        select * from test
    </select>
</mapper>

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.InputStream;
import java.util.List;
import java.util.Map;

/**
 * 一个生活在互联网底层，做着增删改查的码农,不谙世事的造作
 * @create 2021-08-25 21:26
 */
public class TestMain {
    public static void main(String[] args) throws Exception {
        // 1.配置文件编程输入流
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        // 2. 创建SqlSession工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        // 3. 创建SqlSession
        // try里边创建数据流 try语句执行完后流会被自动关闭 但是资源必须实现java.lang.AutoCloseable接口
        // 这叫做 ARM 块(Automatic Resource Management)
        // SqlSession 实现了Closeable  Closeable继承了AutoCloseable接口
        try (SqlSession session = sqlSessionFactory.openSession()) {
            // 4. 执行查询 查列表出来
            List<Map<String,Object>> res = session.selectList("TestMapper.list");
            // 5. 遍历结果输出
            if (res != null) {
                for (int i = 0; i < res.size(); i++) {
                    Map<String,Object> tmp = res.get(i);
                    System.out.println("id="+tmp.get("id")+",name="+
                            tmp.get("name")+",salary="+tmp.get("salary"));
                }
            }
        }
    }
}