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虽然在

以下思路与中的思路基本相同，只不过在2中添加了写一个接口与它对应（EmployeeMapper.interface）

创建一个Employee数据表

创建一个Employee类

package com.atguigu.mybatis.bean;public class Employee {   		private Integer id;	private String lastName;	private String email;	private String gendar;			public Integer getId() {   		return id;	}	public void setId(Integer id) {   		this.id = id;	}	public String getLastName() {   		return lastName;	}	public void setLastName(String lastName) {   		this.lastName = lastName;	}	public String getEmail() {   		return email;	}	public void setEmail(String email) {   		this.email = email;	}	public String getGender() {   		return gendar;	}	public void setGender(String gender) {   		this.gendar = gender;	}	@Override	public String toString() {   		return "Employee [id=" + id + ", lastName=" + lastName + ", email="				+ email + ", gender=" + gendar + "]";	}}

1：在conf文件夹中写一个mybatis-config.xml全局配置文件，并在MyBatisTest测试类中创建一个SqlSessionFactory对象

public SqlSessionFactory getSqlSessionFactory() throws IOException {   		String resource = "mybatis-config.xml";		InputStream inputStream = Resources.getResourceAsStream(resource);		return new SqlSessionFactoryBuilder().build(inputStream);	}

2,3：写一个sql映射文件，并且要把该文件注入到全局配置文件（mybatis-config.xml）中

   
   
    	
    		select id,lastName,email,gendar from Employee where id = #{id}	
   

EmployeeMapper.interface

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

4：在MyBatisTest测试类中写演示代码

package com.atstudying.mybatis.test;import java.io.IOException;import java.io.InputStream;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 com.atstudying.mybatis.bean.Employee;import com.atstudying.mybatis.dao.EmployeeMapper;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 test01() throws IOException {   		// 1、获取sqlSessionFactory对象		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();		// 2、获取sqlSession对象		SqlSession openSession = sqlSessionFactory.openSession();		try {   			// 3、获取接口的实现类对象			//会为接口自动的创建一个代理对象，代理对象去执行增删改查方法			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);			Employee employee = mapper.getEmpById(1);			System.out.println(mapper.getClass());			System.out.println(employee);		} finally {   			openSession.close();		}	}}

查询结果

查询结果我们发现了一个代理对象class com.sun.proxy.$Proxy4，

可以知道在获取接口的实现类对象时调用以下方法会为接口自动创建一个代理对象openSession.getMapper(EmployeeMapper.class);