1、新建一个接口类EmployeeMapper：
package com.gwolf.dao;
import com.gwolf.bean.Employee;
public interface EmployeeMapper {
public Employee queryEmpById(Integer id);
}
2、我们可以实现接口与xml文件绑定，在EmployeeMapper.xml的namespace中指定为EmployeeMapper 的全类名就可以实现接口与xml的绑定：
<?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.gwolf.dao.EmployeeMapper">
<!--
namespace:名称空间
id:唯一标识
resultType:返回值类型
#{empId}:从传递过来的参数取出empId值
-->
<select id="selectEmployee" resultType="com.gwolf.bean.Employee">
select emp_id empId,gender,emp_name empName,email,gender
from tbl_emp where emp_id = #{empId}
</select>
</mapper>
3、然后把Mapper中的方法与xml的sql语句进行绑定，只需要把方法名称和sql语句的id名称一样即可：
<?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.gwolf.dao.EmployeeMapper">
<!--
namespace:名称空间
id:唯一标识
resultType:返回值类型
#{empId}:从传递过来的参数取出empId值
-->
<select id="queryEmpById" resultType="com.gwolf.bean.Employee">
select emp_id empId,gender,emp_name empName,email,gender
from tbl_emp where emp_id = #{empId}
</select>
</mapper>
4、创建一个测试方法，首先获取接口的实现类对象：
@Test
public void test1() throws Exception {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);
}finally {
sqlSession.close();
}
}
5、调用接口的方法：
@Test
public void test1() throws Exception {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
try {
EmployeeMapper employeeMapper = sqlSession.getMapper(EmployeeMapper.class);
Employee employee = employeeMapper.getEmpById(1);
System.out.println(employee);
}finally {
sqlSession.close();
}
}
6、我们虽然没有没有接口的实现类，但是mybatis会自动创建一个代理对象，代理对象会去执行增改查方法。
