MyBatis demo

1. 导 jar 包：mybatis & mysql 驱动

2. 建立数据库、表、插入值
3. 全局配置文件： mybatis-config.xml

   <?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"/>
               <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="root"/>
               </dataSource>
           </environment>
       </environments>
   
       <mappers>
           <mapper resource="EmployeeMapper.xml"/>
       </mappers>
   </configuration>

    

4. 建立数据类型
   Emplyee.java

5. 建立映射文件

   public interface EmployeeMapper {
   	public Employee getEmpById(Integer id);
   }

    

6. 设置映射关系

   <?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="EmployeeMapper">  <!-- 任意。如果是接口式，必须是 mapper 文件的全限定名 -->
   
       <select id="getEmpById" resultType="Employee"> <!-- 任意。如果是接口式，必须是方法名 -->
   		select id,last_name lastName,email,gender from employee where id = #{id}
   	</select>
   
   </mapper>

    

7. 测试

   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 java.io.IOException;
   import java.io.InputStream;
   
   public class MyBatisTest {
     public SqlSessionFactory getSqlSessionFactory() throws IOException {
       String resource = "mybatis-config.xml";
       InputStream inputStream = Resources.getResourceAsStream(resource);
       return new SqlSessionFactoryBuilder().build(inputStream);
     }
   
     @Test
     public void test() throws IOException {
       SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
       SqlSession openSession = sqlSessionFactory.openSession();
       try {
         Employee employee = openSession.selectOne("EmployeeMapper.getEmpById", 1);
         System.out.println(employee);
       } finally {
         openSession.close();
       }
     }
   
     @Test
     public void test01() throws IOException {
       SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
       SqlSession openSession = sqlSessionFactory.openSession();
       try {
         EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
         Employee employee = mapper.getEmpById(1);
         System.out.println(employee);
       } finally {
         openSession.close();
       }
     }
   
   }

    

8. PS:

   1. SqlSession 和 connection 都是非线程安全的，每次使用都应该重新获取新的对象。

   2.