Day5——MyBatis helloworld Mapper接口开发

曾经终败给现在 2023-07-04 11:16 79阅读 0赞

# 一. 回顾 #

前面[Day3——MyBatis的helloworld(不使用Mapper接口实现MyBatis查询数据库）][Day3_MyBatis_helloworld_Mapper_MyBatis]是不适用Mapper接口实现MyBatis，今天讲解使用Mapper接口开发实现MyBatis

### [前往免费下载源码][Link 1] ###

# 二. 知识储备 #

## 2.1 使用Mapper接口实现MyBatis的步骤 ##

1.  提供Mapper接口（其实就是以往自己创建的DAO接口，比如EmployDao.java，现在讲解MyBatis内容，使用Mapper称之，而不是叫DAO）
2.  完成两个绑定

<table> 
 <thead> 
  <tr> 
   <th>绑定</th> 
   <th>说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>Mapper接口与映射文件的绑定</td> 
   <td>SQL映射文件的namespace指定成接口的全类名</td> 
  </tr> 
  <tr> 
   <td>Mapper接口的方法与SQL语句的绑定</td> 
   <td>SQL语句的id值指定成接口的方法名</td> 
  </tr> 
 </tbody> 
</table>

1.  获取MyBatis为Mapper接口生成的代理实现类的对象，如下:

EmployeeMapper mapper = session.getMapper(EmployeeMapper.class);

# 三. 例子 #

*  创建工程，导入jar 包，如下：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNjM0ODQ2_size_16_color_FFFFFF_t_70]
 *  创建测试表，如下：

CREATE TABLE tbl_employee(
      id INT(11) PRIMARY KEY AUTO_INCREMENT,
    	last_name VARCHAR(50),
    	email VARCHAR(50),
    	gender CHAR(1)
    );
    
    INSERT INTO tbl_employee VALUES (1001, '刚哥', 'gg@sina.com', '1');
    
    SELECT * FROM tbl_employee;

*  创建JavaBean，如下：

Employee.java

package com.atguigu.mybatis.beans;
    
    public class Employee { 
         private Integer id;
         private String lastName;
         private String email;
         private String gender;
         
    	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 gender;
    	}
    	
    	public void setGender(String gender) { 
    		this.gender = gender;
    	}
    	
    	@Override
    	public String toString() { 
    		return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email + ", gender=" + gender + "]";
    	}
         
         
    }

*  创建全局配置文件，如下:  
    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/bookstore_0416" />
    				<property name="username" value="root" />
    				<property name="password" value="123456" />
    			</dataSource>
    		</environment>
    	</environments>
    	
    	
    	
    	<mappers>
    		<mapper resource="EmployeeMapper.xml" />
    	</mappers> 
    </configuration>

*  创建映射文件，如下：  
    EmployeeMapper.xml

<?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.atguigu.mybatis.dao.EmployeeMapper">
    	
    	
    	<select id="selectEmployeeById" resultType="com.atguigu.mybatis.beans.Employee">
    	    select id, last_name lastName, email, gender from tbl_employee where id = #{id}
    	</select>
    	
    </mapper>

*  创建Mapper接口，如下：  
    EmployeeMapper.java

package com.atguigu.mybatis.dao;
    
    import com.atguigu.mybatis.beans.Employee;
    
    public interface EmployeeMapper { 
    
    	public Employee selectEmployeeById(Integer id);
    	
    }

*  创建测试方法，如下：

package com.atguigu.mybatis.test;
    
    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.atguigu.mybatis.beans.Employee;
    import com.atguigu.mybatis.dao.EmployeeMapper;
    
    public class TestMyBatis { 
    	@Test
    	public void helloWorldMapper() throws Exception { 
    		String resource = "mybatis-config.xml"; 
    		InputStream inputStream = 
    				Resources.getResourceAsStream(resource); 
    		SqlSessionFactory sqlSessionFactory = 
    				new SqlSessionFactoryBuilder().build(inputStream);
    		
    		SqlSession session = sqlSessionFactory.openSession(); 
    		
    		try { 
    			EmployeeMapper mapper = session.getMapper(EmployeeMapper.class);
    			Employee employee = mapper.selectEmployeeById(1001);
    			System.out.println(employee);
    		} finally { 
    			// TODO: handle finally clause
    			session.close();
    		}
    
    	}

*  测试结果，如下：  
    ![在这里插入图片描述][20200210151637108.PNG]

[Day3_MyBatis_helloworld_Mapper_MyBatis]: https://blog.csdn.net/qq_40634846/article/details/104247689
[Link 1]: https://me.csdn.net/download/qq_40634846
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNjM0ODQ2_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200210151114300.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNjM0ODQ2,size_16,color_FFFFFF,t_70
[20200210151637108.PNG]: https://img-blog.csdnimg.cn/20200210151637108.PNG