spring-mybatis —— MapperFactoryBean之数据映射文件

水深无声 2021-06-24 14:36 387阅读 0赞

为了代替手工使用 SqlSessionDaoSupport 或 SqlSessionTemplate 编写数据访问对象(DAO)的代码,MyBatis-Spring 提供了一个动态代理的实现——MapperFactoryBean。这个类可以让你直接注入数据映射器接口到你的 service 层bean 中。当使用映射器时,你仅仅如调用你的 DAO 一样调用它们就可以了,但是你不需要编写任何 DAO 实现的代码,因为 MyBatis-Spring将会为你创建代理。同样，MapperFactoryBean创建的代理控制开放和关闭 session。

在使用MapperFactoryBean时，可以通过映射接口方式提供sql语句，也可以通过映射文件提供sql语句。下面讲解如何使用映射文件提供sql

1、spring.xml

<?xml version="1.0" encoding="UTF-8"?>  
 <beans xmlns="http://www.springframework.org/schema/beans"  
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"  
     xmlns:context="http://www.springframework.org/schema/context"  
     xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"  
     xsi:schemaLocation="http://www.springframework.org/schema/beans   
             http://www.springframework.org/schema/beans/spring-beans-3.0.xsd   
             http://www.springframework.org/schema/mvc   
             http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd   
             http://www.springframework.org/schema/context   
             http://www.springframework.org/schema/context/spring-context-3.0.xsd   
             http://www.springframework.org/schema/aop   
             http://www.springframework.org/schema/aop/spring-aop-3.0.xsd   
             http://www.springframework.org/schema/tx   
             http://www.springframework.org/schema/tx/spring-tx-3.0.xsd ">  
    <context:annotation-config />
   
       
     <context:component-scan base-package="cn.edu.nuc" />  
       
     <context:property-placeholder location="classpath:jdbc.properties" />  
       
       
     <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">  
         <property name="driverClass" value="${jdbc.driverClassName}" />  
         <property name="jdbcUrl" value="${jdbc.url}" />  
         <property name="user" value="${jdbc.username}" />  
         <property name="password" value="${jdbc.password}" />  
         <property name="maxPoolSize" value="${c3p0.pool.size.max}" />  
         <property name="minPoolSize" value="${c3p0.pool.size.min}" />  
         <property name="initialPoolSize" value="${c3p0.pool.size.ini}" />  
         <property name="acquireIncrement" value="${c3p0.pool.size.increment}" />  
     </bean>
      
    
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">  
         <property name="dataSource" ref="dataSource" />  
         <property name="configLocation" value="classpath:mybatis/configuration.xml"/>
         <property name="mapperLocations" value="classpath*:cn/edu/nuc/map/*.xml"/>
    </bean>
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
 	    
 	    <property name="basePackage" value="cn.edu.nuc.map"/>
 	    <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/>
 	</bean>
 </beans>

<?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>
 	<settings>
 		
 		<setting name="cacheEnabled" value="false" />
 		<setting name="useGeneratedKeys" value="true" />
 		<setting name="defaultExecutorType" value="REUSE" />
 		<setting name="lazyLoadingEnabled" value="false" />
 		<setting name="logImpl" value="LOG4J" />
 	</settings>
 	<mappers>
 
 	</mappers>
 </configuration>

2、映射接口：

package cn.edu.nuc.map;
    
    import org.springframework.stereotype.Component;
    
    import cn.edu.nuc.bean.User;
    
    @Component("UserMapper")
    public interface UserMapper1 {
    	
    	User findUserById(long id) throws Exception;
    
    }

3、映射文件：

<?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="cn.edu.nuc.map.UserMapper1">
 <resultMap type="cn.edu.nuc.bean.User" id="userMap">
 <id property="id" column="id" />
 <result property="name" column="name" />
 </resultMap>
 
 <select id="findUserById" parameterType="long" resultMap="userMap">
 select * from user where id = #{id}
 </select>
 
 </mapper>

4、测试：

import org.junit.Before;
    import org.junit.Test;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import cn.edu.nuc.bean.User;
    import cn.edu.nuc.map.UserMapper1;
    
    public class UserServiceMapTest {
    	
    	private ApplicationContext applicationContext;
    
    	//在setUp这个方法得到spring容器
    	@Before
    	public void setUp() throws Exception {
    		applicationContext = new ClassPathXmlApplicationContext("classpath:spring.xml");
    	}
    	
    	
    	@Test
    	public void testFindUserById() throws Exception {
    		UserMapper1 userMapper = (UserMapper1)applicationContext.getBean("UserMapper");
    		//调用userMapper的方法
    		User user = userMapper.findUserById(1);
    		System.out.println(user.getName());
    
    	}
    
    }

使用这种方式时，一定要注意一下几点：

1）Mapper映射文件中：namespace必须和数据映射器接口UserMapper的包名一致；

2）Mapper映射文件中：sql的id必须和数据映射器接口UserMapper的方法名一致；

参考：[http://www.oschina.net/question/113302\_228910?fromerr=dJY106iE][http_www.oschina.net_question_113302_228910_fromerr_dJY106iE]

[http_www.oschina.net_question_113302_228910_fromerr_dJY106iE]: http://www.oschina.net/question/113302_228910?fromerr=dJY106iE