Mybatis入门

Mybatis

笔者建立的是maven 项目，使用的是mysql
在pom.xml 中添加mybatis依赖和mysql依赖

        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>

        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.6</version>
        </dependency>

然后是mybatis配置文件：
mybatis_config.xml:

<?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.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/bookSystem"/>
                <property name="username" value="root"/>
                <property name="password" value="XXX"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

其中<mappers></mappers>中的 <mapper resource="UserMapper.xml"/> 是指定该项目所有的映射文件

UserMapper.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="UserMapper">
    <select id="selectUser" resultType="pojo.User">
        select * from User where userId = #{id}
    </select>
</mapper>

其中<select>用于select方法，id会在调用时候使用，resultType需要确保能够在当前路径下找到

最后就是运行：
Application.java

import pojo.User;
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.IOException;
import java.io.InputStream;

public class Application {

    public static void main(String[] args) throws IOException {
        String resource = "mybatis_config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        SqlSession session = sqlSessionFactory.openSession();
        try {
            User user = session.selectOne("selectUser", 1);
            System.out.println(user);
        } finally {
            session.close();
        }
    }
}

成功运行