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// mybatis配置文件
 String r = "mybatis-config.xml";
 //第一步：获取输入流对象
InputStream is = Resources.getResourceAsStream(r);
//第二步：SqlSessionFactoryBuilder 构造器模式构建一个SqlSessionFactory工厂对象
SqlSessionFactory sqlSessionFactory = new  SqlSessionFactoryBuilder().build(is);
//第三步： 创建sqlSession对象
 SqlSession sqlSession = sqlSessionFactory.openSession(true);
 //调用getMapper方法创建mapper接口对象
UserMapper userMapper = sqlSession.getMapper(UserMapper.class); User user = userMapper.myGetUserById(1);
 System.out.println(user);

其中 mybatis-config.xml文件为：

<?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>
<!-- 引入外部资源文件 -->
<properties resource="jdbc.properties"></properties>
<!-- 设置驼峰匹配 -->
<settings>
  <setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>
<!-- 设置包扫描(别名) -->
<typeAliases>
  <package name="cn.itcast.pojo"/>
</typeAliases>
<!-- 配置环境：可以配置多个环境，default：配置某一个环境的唯一标识，表示默认使用哪个环境 -->
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
      	<!-- 配置连接信息 -->
        <property name="driver" value="${jdbc.driverClass}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
      </dataSource>
    </environment>
  </environments>
  <!-- 配置映射文件：用来配置sql语句和结果集类型等 -->
  <mappers>
    <mapper resource="UserMapper.xml"/>
  </mappers>
</configuration>

其中 jdbc.properties配置参考为：

jdbc.driverClass=com.mysql.jdbc.Driver
jdbc.url
=jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC
jdbc.username=root
jdbc.password=123456