create database mybatis;

 use mybatis;

 CREATE TABLE users(id INT PRIMARY KEY AUTO_INCREMENT, NAME VARCHAR(20), age INT);

 INSERT INTO users(NAME, age) VALUES('孤傲苍狼', );

 INSERT INTO users(NAME, age) VALUES('白虎神皇', );

 <?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" />

             <!-- 配置数据库连接信息 -->

             <dataSource type="POOLED">

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

                 <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />

                 <property name="username" value="root" />

                 <property name="password" value="XDP" />

             </dataSource>

         </environment>

     </environments>

 </configuration>

 package me.gacl.domain;

 /**

  * @author gacl

  * users表所对应的实体类

  */

 public class User {

     //实体类的属性和表的字段名称一一对应

     private int id;

     private String name;

     private int age;

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public int getAge() {

         return age;

     }

     public void setAge(int age) {

         this.age = age;

     }

     @Override

     public String toString() {

         return "User [id=" + id + ", name=" + name + ", age=" + age + "]";

     }

 }

 <?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">

 <!-- 为这个mapper指定一个唯一的namespace，namespace的值习惯上设置成包名+sql映射文件名，这样就能够保证namespace的值是唯一的

 例如namespace="me.gacl.mapping.userMapper"就是me.gacl.mapping(包名)+userMapper(userMapper.xml文件去除后缀)

  -->

 <mapper namespace="me.gacl.mapping.userMapper">

     <!-- 在select标签中编写查询的SQL语句， 设置select标签的id属性为getUser，id属性值必须是唯一的，不能够重复

     使用parameterType属性指明查询时使用的参数类型，resultType属性指明查询返回的结果集类型

     resultType="me.gacl.domain.User"就表示将查询结果封装成一个User类的对象返回

     User类就是users表所对应的实体类

     -->

     <!--

         根据id查询得到一个user对象

      -->

     <select id="getUser" parameterType="int"

         resultType="me.gacl.domain.User">

         select * from users where id=#{id}

     </select>

 </mapper>

 <?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" />

             <!-- 配置数据库连接信息 -->

             <dataSource type="POOLED">

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

                 <property name="url" value="jdbc:mysql://localhost:3306/mybatis" />

                 <property name="username" value="root" />

                 <property name="password" value="XDP" />

             </dataSource>

         </environment>

     </environments>

     <mappers>

         <!-- 注册userMapper.xml文件，

         userMapper.xml位于me.gacl.mapping这个包下，所以resource写成me/gacl/mapping/userMapper.xml-->

         <mapper resource="me/gacl/mapping/userMapper.xml"/>

     </mappers>

 </configuration>

package me.gacl.test;

import java.io.IOException;

import java.io.InputStream;

import java.io.Reader;

import me.gacl.domain.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;

public class Test1 {

    public static void main(String[] args) throws IOException {

        //mybatis的配置文件

        String resource = "conf.xml";

        //使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）

        InputStream is = Test1.class.getClassLoader().getResourceAsStream(resource);

        //构建sqlSession的工厂

        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);

        //使用MyBatis提供的Resources类加载mybatis的配置文件（它也加载关联的映射文件）

        //Reader reader = Resources.getResourceAsReader(resource);

        //构建sqlSession的工厂

        //SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);

        //创建能执行映射文件中sql的sqlSession

        SqlSession session = sessionFactory.openSession();

        /**

         * 映射sql的标识字符串，

         * me.gacl.mapping.userMapper是userMapper.xml文件中mapper标签的namespace属性的值，

         * getUser是select标签的id属性值，通过select标签的id属性值就可以找到要执行的SQL

         */

        String statement = "me.gacl.mapping.userMapper.getUser";//映射sql的标识字符串

        //执行查询返回一个唯一user对象的sql

        User user = session.selectOne(statement, 1);

        System.out.println(user);

    }

}