作为一个众多互联网后台开发工作者的一员，在日常工作中，常常利用一些现成的工具来解决一些实际的问题，但有一些工具只是局限于使用，而没有进一步了解。本系列blog是blog主希望加深对日常工作中经常使用的一些工具有进一步的了解。
要了解一个工具最最直接的方法是直接看这个工具的官网。http://www.mybatis.org/mybatis-3/zh/index.html
blog不想从复制一个mybatis官网，而是希望从自己的角度去理解，由于水平有限，过程中难免会参考一些网上的东西。

mybatis是个什么东西

MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解，将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录。

知道了什么东西，不管三七二十一，先用起来

1.首先先安装个数据库，本人是在ubuntu下安装的mysql

sudo apt-get install mysql-server
sudo apt-get install mysql-client
sudo apt-get install libmysqlclient-dev

2.建表

create database test;
use test;
create table student
(
 student_id int primary key auto_increment not null comment "学生id",
 student_name varchar(20) not null comment "学生姓名",
 student_age int not null comment "学生年龄",
 student_phone varchar(20) not null comment "学生电话"
) charset=utf8 comment "学生信息表";
insert into student values(null, 'Jack', 20, '000000');
insert into student values(null, 'Mark', 21, '111111');
insert into student values(null, 'Lily', 22, '222222');
insert into student values(null, 'Lucy', 23, '333333');

3.添加config.xml配置文件

<?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>
   <typeAliases>
       <typeAlias alias="Student" type="com.yongssu.mybatis.demo1.Student"/>
   </typeAliases>

   <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/test"/>
               <property name="username" value="root"/>
               <property name="password" value="123456"/>
           </dataSource>
       </environment>
   </environments>

   <mappers>
       <mapper resource="student.xml"/>
   </mappers>
</configuration>

4.声明一个java类，对应student表

public class Student {
   private int student_id;
   private String student_name;
   private int student_age;
   private String student_phone;
   public Student() {
       super();
   }
   public int getStudent_id() {
       return student_id;
   }
   public void setStudent_id(int student_id) {
       this.student_id = student_id;
   }
   public String getStudent_name() {
       return student_name;
   }
   public void setStudent_name(String student_name) {
       this.student_name = student_name;
   }
   public int getStudent_age() {
       return student_age;
   }
   public void setStudent_age(int student_age) {
       this.student_age = student_age;
   }
   public String getStudent_phone() {
       return student_phone;
   }
   public void setStudent_phone(String student_phone) {
       this.student_phone = student_phone;
   }
   @Override
   public String toString() {
       return "Student{" +
               "student_id=" + student_id +
               ", student_name='" + student_name + '\'' +
               ", student_age=" + student_age +
               ", student_phone='" + student_phone + '\'' +
               '}';
   }
}

5.配置student.xml文件

<?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="com.yongssu.mybatis.demo1.StudentMapper">
   <select id="selectStudentById" parameterType="int" resultType="Student">
       <![CDATA[
           select * from student where student_id = #{id}
       ]]>
   </select>
   <select id="selectStudent" parameterType="int" resultType="Student">
       <![CDATA[
           select * from student where student_id = #{id}
       ]]>
   </select>
</mapper>

6.声明StudentMapper类

public interface StudentMapper {
   Student selectStudent(int id);

   @Select("select * from student where student_id = #{id}")
   Student selectStudent2(int id);
}

7.最终的测试类

public class MybatisTest {
   private static SqlSessionFactory sqlSessionFactory;
   static {
       try {
           Reader reader = Resources.getResourceAsReader("config.xml");
           sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
       } catch (IOException e) {
           e.printStackTrace();
       }
   }

   public static void main(String[] args) throws IOException {
       test01();
       test02();
       test03();
   }

   /**
    * 通过xml配置实现sql查询
    * @throws IOException
    */
   public static void test01() throws IOException {
       // 执行sql
       SqlSession sqlSession = sqlSessionFactory.openSession();
       try {
           Student student = sqlSession.selectOne("com.yongssu.mybatis.demo1.StudentMapper.selectStudentById", 1);
           System.out.println(student);
       } finally {
           sqlSession.close();
       }
   }

   /**
    * 通过接口+xml配置实现sql查询
    * @throws IOException
    */
   public static void test02() throws IOException {
       // 执行sql
       SqlSession session = sqlSessionFactory.openSession();
       try {
           StudentMapper mapper = session.getMapper(StudentMapper.class);
           Student student = mapper.selectStudent(2);
           System.out.println(student);
       } finally {
           session.close();
       }
   }

   /**
    * 通过注解实现sql查询
    * @throws IOException
    */
   public static void test03() throws IOException {
       // 执行sql
       SqlSession session = sqlSessionFactory.openSession();
       try {
           StudentMapper mapper = session.getMapper(StudentMapper.class);
           Student student = mapper.selectStudent2(3);
           System.out.println(student);
       } finally {
           session.close();
       }
   }
}

最后声明

记得引入mybatis jar包.运行之后应该能看到三条数据.