driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://192.168.8.136:3306/mybatis
username=root
password=root

<!-- 外部 properties 配置文件  -->
<properties resource="db.properties"/>

<!--配置数据源-->
<environments default="development-mysql">
    <environment id="development-mysql">
        <transactionManager type="JDBC"/>
        <dataSource type="POOLED">
            <property name="driver" value="${driver}"/>
            <property name="url" value="${url}"/>
            <property name="username" value="${username}"/>
            <property name="password" value="${password}"/>
        </dataSource>
    </environment>
</environments>

<settings>
    <!-- 数据库字段下划线转 Bean 字段的驼峰命名 -->
    <setting name="mapUnderscoreToCamelCase" value="true"/>
    <!-- 控制台打印SQL -->
    <setting name="logImpl" value="STDOUT_LOGGING" />
</settings>

<!-- typeAliases：别名处理器：可以为 JavaBean 类型起别名,别名不区分大小写 -->
<typeAliases>
    <!-- typeAlias:为某个java类型起别名,type:指定要起别名的类型全类名;默认别名就是类名小写,alias:指定新的别名 -->
    <!--<typeAlias type="com.bean.MyUser" alias="myUser"/>-->

    <!-- package:为某个包下的所有类批量起别名,name：指定包名,为当前包以及下面所有的后代包的每一个类都起一个默认别名（类名小写） -->
    <package name="com.bean"/>

    <!-- 批量起别名的情况下，可以在 Bean 上使用 @Alias 注解为某个类指定新的别名 -->
</typeAliases>

<?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">
<!-- namespace 对应接口文件的全路径 -->
<mapper namespace="com.dao.MyUserMapper">
    <!-- id 与接口文件方法名对应,resultType 设置别名后返回类型可写别名 -->
    <!--<select id="selectMyUser" resultType="com.bean.MyUser">-->
    <select id="selectMyUser" resultType="myUser">
      select * from myuser where id = #{id}
    </select>
</mapper>

<!-- environments：环境配置,default 指定使用某种环境
     environment：配置具体环境信息；有两个标签；id代表当前环境唯一标识
        transactionManager：事务管理器
            type：事务管理器的类型 JDBC(JdbcTransactionFactory) | MANAGED(ManagedTransactionFactory)
            自定义事务管理器：实现 TransactionFactory 接口,type 为全类名
        dataSource：数据源
            type:数据源类型 UNPOOLED(UnpooledDataSourceFactory) | POOLED(PooledDataSourceFactory) | JNDI(JndiDataSourceFactory)
            自定义数据源：实现 DataSourceFactory 接口，type 为全类名 -->
<environments default="development-dev">
    <environment id="development-dev">
        <transactionManager type="JDBC"/>
        <dataSource type="POOLED">
            <property name="driver" value="${driver}"/>
            <property name="url" value="${url}"/>
            <property name="username" value="${username}"/>
            <property name="password" value="${password}"/>
        </dataSource>
    </environment>

    <environment id="development-sit">
        <transactionManager type="MANAGED"/>
        <dataSource type="UNPOOLED">
            <property name="driver" value="${sit.driver}"/>
            <property name="url" value="${sit.url}"/>
            <property name="username" value="${sit.username}"/>
            <property name="password" value="${sit.password}"/>
        </dataSource>
    </environment>
</environments>

<!-- environments：环境配置,default 指定使用某种环境
     environment：配置具体环境信息；有两个标签；id代表当前环境唯一标识
        transactionManager：事务管理器
            type：事务管理器的类型 JDBC(JdbcTransactionFactory) | MANAGED(ManagedTransactionFactory)
            自定义事务管理器：实现 TransactionFactory 接口,type 为全类名
        dataSource：数据源
            type:数据源类型 UNPOOLED(UnpooledDataSourceFactory) | POOLED(PooledDataSourceFactory) | JNDI(JndiDataSourceFactory)
            自定义数据源：实现 DataSourceFactory 接口，type 为全类名 -->
<environments default="development-mysql">
    <environment id="development-mysql">
        <transactionManager type="JDBC"/>
        <dataSource type="POOLED">
            <property name="driver" value="${driver}"/>
            <property name="url" value="${url}"/>
            <property name="username" value="${username}"/>
            <property name="password" value="${password}"/>
        </dataSource>
    </environment>

    <environment id="development-oracle">
        <transactionManager type="MANAGED"/>
        <dataSource type="UNPOOLED">
            <property name="driver" value="${oracle.driver}"/>
            <property name="url" value="${oracle.url}"/>
            <property name="username" value="${oracle.username}"/>
            <property name="password" value="${oracle.password}"/>
        </dataSource>
    </environment>
</environments>

<!-- databaseIdProvider：支持多数据库厂商
    type="DB_VENDOR"：VendorDatabaseIdProvider 作用是得到数据库厂商的标识(JDBC getDatabaseProductName())，mybatis 就能根据数据库厂商标识来执行不同的 SQL -->
<databaseIdProvider type="DB_VENDOR">
    <!-- 为不同的数据库厂商起别名 -->
    <property name="MySQL" value="mysql"/>
    <property name="Oracle" value="oracle"/>
    <property name="SQL Server" value="sqlserver"/>
</databaseIdProvider>

<?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">
<!-- namespace 对应接口文件的全路径 -->
<mapper namespace="com.dao.MyUserMapper">
    <!--找不到对应数据库 SQL 语句时会执行默认-->
    <select id="selectMyUser" resultType="myUser">
      select * from myuser where id = #{id}
    </select>
    <!-- databaseId 对应数据库别名 -->
    <select id="selectMyUser" resultType="myUser" databaseId="mysql">
      select * from myuser where id = #{id}
    </select>
    <select id="selectMyUser" resultType="myUser" databaseId="oracle">
      select * from myuser where id = #{id}
    </select>
</mapper>

<mappers>
    <!-- 引用类路径下的 SQL 映射文件 -->
    <mapper resource="com/dao/MyUserMapper.xml"/>
</mappers>

<mappers>
    <!-- 引用网路路径或者磁盘路径下的sql映射文件 -->
    <mapper url="file:///var/mappers/AuthorMapper.xml"/> 
</mappers>

<mappers>
    <!-- 引用 Class 接口注册,没有 SQL 映射文件，所有的 SQL 都是利用注解写在接口上 -->
    <mapper class="com.dao.MyUserMapperAnnotation"/>
</mappers>

import com.bean.MyUser;
import org.apache.ibatis.annotations.Select;

public interface MyUserMapperAnnotation {
    @Select("select * from myuser where id = #{id}")
    public MyUser selectMyUser(Integer id);
}

import com.bean.MyUser;
import com.dao.MyUserMapperAnnotation;

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 Main {
    public static void main(String[] args) {
        SqlSession session = null;
        try {
            String resource = "mybatis-config2.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            session = sqlSessionFactory.openSession();

            MyUserMapperAnnotation mapper = session.getMapper(MyUserMapperAnnotation.class);
            MyUser myUser = (MyUser) mapper.selectMyUser(1);
            System.out.println(myUser);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (session != null) {
                session.close();
            }
        }
    }
}

<mappers>
    <!-- 批量注册,映射文件名必须和接口同名，且放在与接口同一层级目录下 -->
    <package name="com.dao"/>
</mappers>