Mybatis学习(1) -- 快速入门

 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', 27);



 INSERT INTO users(NAME, age) VALUES('白虎神皇', 27);

 



  <?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);



    }



}