Java框架MyBatis接口编程过程解析

package com.bird.mybatis.dao;
import com.bird.mybatis.bean.Employee;
public interface EmployeeMapper {
 public Employee getEmpById(Integer id); 
}

<?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">
 
<!-- namespace:名称空间(若使用接口式编程,与EmployeeMapper接口全类名一致)
 id:唯一标识(与接口中的方法名对应)
 resultType:返回值类型(与对应方法的返回值对应)
 #{id}:从传递过来的参数中取出id值
 -->
<mapper namespace="com.bird.mybatis.dao.EmployeeMapper">
 <select id="getEmpById" resultType="com.bird.mybatis.bean.Employee"> 
  select id,last_name lastName,gender,email from tbl_employee where id = #{id}
 </select>
</mapper>

/**
  * MyBatis接口编程
  * @throws IOException 
  */
 @Test
 void test2() throws IOException {
  //获取sqlSessionFactory对象
  SqlSessionFactory ssf = getSqlSessionFactory();
  //获取sqlSession对象
  SqlSession openSession = ssf.openSession();
  try {
   //获取接口的实现类对象
   EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
   Employee empById = mapper.getEmpById(1);
   System.out.println(empById);
  }finally {
   openSession.close();
  }
 }
 
 /**
  * 获取sqlSessionFactory对象
  * @throws IOException 
  */
 public static SqlSessionFactory getSqlSessionFactory() throws IOException {
  String resource = "mybatis-config.xml";
  InputStream is = Resources.getResourceAsStream(resource);
  return new SqlSessionFactoryBuilder().build(is);
 }