Day3——MyBatis的helloworld(不使用Mapper接口实现MyBatis查询数据库）

雨点打透心脏的1/2处 2023-07-04 11:14 75阅读 0赞

# 一. 知识储备 #

### [前往免费下载源码][Link 1] ###

## 1.1 使用MyBatis查询数据库步骤 ##

1.  搭建环境：创建Java Project，导入jar包（mybatis jar包、mysql-connector-java jar包、log4j jar包）
2.  准备测试表、javaBean
3.  创建全局的配置文件：mybatis-config.xml
4.  获取SqlSessionFactory对象
5.  创建SQL映射文件：xxxMapper.xml(一般情况你想要操作的类名是什么，xxx就写什么，比如我想要操作Employee，映射文件就写EmployeeMapper.xml）
6.  测试查询

# 二. 例子 #

*  首先创建好名为Mybatis的Java Project，new好名为conf的source folder，new好名为lib的folder。导入jar包，项目结构图如下：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNjM0ODQ2_size_16_color_FFFFFF_t_70]
 *  创建名为bookstore\_0416数据库，创建名为tbl\_employee的表，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;

结果如下：  
![在这里插入图片描述][20200210140522647.PNG]

*  创建名为Employee的JavaBean，如下：

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：位于conf源文件夹下，名为mybatis-config.xml，如下:

<?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>

*  获取SqlSessionFactory对象，如下:

TestMyBatis.java

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;
    
    public class TestMyBatis { 
    
    	
    	@Test
    	public void testHelloWorld() throws Exception{ 
    		String resource = "mybatis-config.xml"; 
    		InputStream inputStream = 
    				Resources.getResourceAsStream(resource); 
    		SqlSessionFactory sqlSessionFactory = 
    				new SqlSessionFactoryBuilder().build(inputStream);
    		
    		SqlSession session = sqlSessionFactory.openSession(); 
    		try {   
    			/** * Parameters: * statement Unique identifier matching the statement to use.即SQL语句的唯一标识 * parameter A parameter object to pass to the statement.即执行sql语句的参数 * Returns: * Mapped object */
    			
    			Employee employee = 
    					session.selectOne("suibian.selectBlog", 1001); 
    			System.out.println("employee: " + employee);
    		} finally {   
    		  session.close(); 
    		}
    	}
    }

*  创建SQL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="suibian">
    	
    	<select id="selectBlog" resultType="com.atguigu.mybatis.beans.Employee"> 
    	  select id, last_name lastName, email, gender from tbl_employee where id = #{id}  
    	</select>
    </mapper>

*  测试结果：

![在这里插入图片描述][20200210141614701.PNG]

[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/20200210140336438.PNG?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNjM0ODQ2,size_16,color_FFFFFF,t_70
[20200210140522647.PNG]: https://img-blog.csdnimg.cn/20200210140522647.PNG
[20200210141614701.PNG]: https://img-blog.csdnimg.cn/20200210141614701.PNG