mybatis整体流程

<?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>

    <!-- <properties>
        <property name="jdbc.driver" value="com.mysql.jdbc.Driver"/>
    </properties> -->

    <!--
        <properties>:设置或引入资源文件
        resource:在类路径下访问资源文件
        url:在网络路径或磁盘路径下访问资源文件
     -->
    <properties resource="jdbc.properties"></properties>

    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <typeAliases>
        <!--
            为类型设置类型别名
            type:Java 类型，若只设置type，默认的别名就是类型，且不区分大小写
         -->
        <!-- <typeAlias type="com.atguigu.bean.User" alias="u"/> 不建议-->
        <!-- 这种写法在XxxMapper.xml的resultType只需要写个Xxx就可以 -->
        <package name="com.atguigu.bean"/>
    </typeAliases>

    <!--
        <environments>:设置连接数据库的环境
        default:设置默认使用的数据库环境
     -->
    <environments default="mysql">
        <!--
            <environment>:设置某个具体的数据库的环境
            id:数据库环境的唯一标示
         -->
        <environment id="mysql">
            <!-- type="JDBC|MANAGED" -->
            <transactionManager type="JDBC" />
            <!-- type="POOLED|UNPOOLED|JNDI" -->
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}" />
                <property name="url" value="${jdbc.url}" />
                <property name="username" value="${jdbc.username}" />
                <property name="password" value="${jdbc.password}" />
            </dataSource>
        </environment>

        <environment id="oracle">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/ssm" />
                <property name="username" value="root" />
                <property name="password" value="123456" />
            </dataSource>
        </environment>
    </environments>
    <!-- 引入映射文件 -->
    <mappers>
    <!-- 引入具体的映射文件 -->
        <mapper resource="UserMapper.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">

 <!-- 这个用来指定对应的dao接口 -->
<mapper namespace="com.atguigu.mapper.UserMapper">

    <!--
        <select>:定义查询语句
        id:设置SQL语句的唯一标示
        resultType:结果类型，即实体类的全限定名
        resultType如果在sqlMapConfig.xml中配置过typeAlisas，则按起的别名来，不建议
     -->
    <select id="getUserByUid" resultType="com.atguigu.bean.User">
        select uid,username,password,age,sex from user where uid = ${value}
    </select>

</mapper>

package com.atguigu.mapper;

import com.atguigu.bean.User;

public interface UserMapper {
    //和UserMapper.xml中的sql的id对应的
    /**
     * <!--
        <select>:定义查询语句
        id:设置SQL语句的唯一标示
        resultType:结果类型，即实体类的全限定名
     -->
    <select id="getUserByUid" resultType="com.atguigu.bean.User">
        select uid,username,password,age,sex from user where uid = ${value} 或者#{id}
    </select>

     * @param uid
     * @return
     */
    User getUserByUid(String uid);

}

package com.atguigu.mapper;

import static org.junit.Assert.*;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

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 org.junit.Test;

import com.atguigu.bean.User;

public class TestMybatis {

    @Test
    public void test() throws IOException {

        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");//org.apache.ibatis.io.Resources
        //InputStream is = TestMybatis.class.getClassLoader().getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory =
                new SqlSessionFactoryBuilder().build(is);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //getMapper():会通过动态代理动态生成UserMapper的代理实现类
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        System.out.println(mapper.getClass().getName());//com.sun.proxy.$Proxy4这个为生成的代理对象
        User user = mapper.getUserByUid("1");
        System.out.println(user);
        //user_name ---> userName
    }

}