八、Mybatis整合spring之Mapper接口代理实现dao层

阅读本篇文章前建议先看看七、Mybatis整合spring之手动实现dao层

环境准备

我这里直接复制上篇文章的工程&＃xff0c;然后将dao层删掉&＃xff0c;把user.xml映射文件删掉&＃xff0c;测试类删掉&＃xff0c;删掉SqlMapConfig.xml配置中的user.xml的关联&＃xff0c;删掉ApplicationContext.xml配置中的userDao的注入。

完成后的工程如下所示&＃xff1a;

添加Mapper相关的操作

1.创建UserMapper接口类
在src目录下的根包中创建一个mapper包&＃xff0c;定义UserMapper接口类

package blog.csdn.net.mchenys.mapper;import blog.csdn.net.mchenys.pojo.User;public interface UserMapper {public User findUserById(Integer id);
}

2.创建对应的mapper映射文件
在mapper包中创建UserMapper.xml文件&＃xff0c;注意必须要和接口文件在同一个包下&＃xff0c;配置内容如下&＃xff1a;


PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace&＃61;"blog.csdn.net.mchenys.mapper.UserMapper"><select id&＃61;"findUserById" parameterType&＃61;"java.lang.Integer" resultType&＃61;"blog.csdn.net.mchenys.pojo.User">select * from user where id &＃61; #{id}select>
mapper>


完成后的包结构是这样的&＃xff1a;

3.修改Mybatis配置文件

编辑SqlMapConfig.xml&＃xff0c;在mappers节点开启包扫描的方式引入Mapper接口类


PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><mappers> <package name&＃61;"blog.csdn.net.mchenys.mapper"/>mappers>
configuration>


修改Spring配置文件

这里有2种方式接入Mapper接口的代理实现类&＃xff0c;先介绍手动注入的方式&＃xff0c;编辑ApplicationContext.xml&＃xff0c;在beans标签节点内添加如下内容&＃xff1a;

<bean id&＃61;"userMapper" class&＃61;"org.mybatis.spring.mapper.MapperFactoryBean"><property name&＃61;"mapperInterface" value&＃61;"cn.itheima.mapper.UserMapper">property><property name&＃61;"sqlSessionFactory" ref&＃61;"sqlSessionFactory">property>bean>


关于org.mybatis.spring.mapper.MapperFactoryBean可以在mybatis-spring-1.2.2.jar中找到

完整的Spring配置文件如下&＃xff1a;


<beans xmlns&＃61;"http://www.springframework.org/schema/beans"xmlns:context&＃61;"http://www.springframework.org/schema/context" xmlns:p&＃61;"http://www.springframework.org/schema/p"xmlns:aop&＃61;"http://www.springframework.org/schema/aop" xmlns:tx&＃61;"http://www.springframework.org/schema/tx"xmlns:xsi&＃61;"http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation&＃61;"http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsdhttp://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsdhttp://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd"><context:property-placeholder location&＃61;"classpath:db.properties" /><bean id&＃61;"dataSource" class&＃61;"org.apache.commons.dbcp.BasicDataSource"destroy-method&＃61;"close"><property name&＃61;"driverClassName" value&＃61;"${jdbc.driver}" /><property name&＃61;"url" value&＃61;"${jdbc.url}" /><property name&＃61;"username" value&＃61;"${jdbc.username}" /><property name&＃61;"password" value&＃61;"${jdbc.password}" /><property name&＃61;"maxActive" value&＃61;"10" /><property name&＃61;"maxIdle" value&＃61;"5" />bean><bean id&＃61;"sqlSessionFactory" class&＃61;"org.mybatis.spring.SqlSessionFactoryBean"><property name&＃61;"configLocation" value&＃61;"classpath:SqlMapConfig.xml">property><property name&＃61;"dataSource" ref&＃61;"dataSource">property>bean><bean id&＃61;"userMapper" class&＃61;"org.mybatis.spring.mapper.MapperFactoryBean"><property name&＃61;"mapperInterface" value&＃61;"blog.csdn.net.mchenys.mapper.UserMapper">property><property name&＃61;"sqlSessionFactory" ref&＃61;"sqlSessionFactory">property>bean>beans>


测试

在测试包内创建UserMapperTest测试类

package blog.csdn.net.mchenys.test;import org.junit.Before;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;import blog.csdn.net.mchenys.mapper.UserMapper;
import blog.csdn.net.mchenys.pojo.User;public class UserMapperTest {private ApplicationContext applicatonContext;&＃64;Beforepublic void setUp() throws Exception {applicatonContext &＃61; new ClassPathXmlApplicationContext("ApplicationContext.xml");}&＃64;Testpublic void testFindUserById() throws Exception{UserMapper userMapper &＃61; (UserMapper)applicatonContext.getBean("userMapper");User user &＃61; userMapper.findUserById(1);System.out.println(user);}
}

执行后&＃xff0c;绿条

控制台结果如下&＃xff0c;说明Mapper接口代理的方式也整合Spring也ok了。

优化

上面修改Spring配置文件的时候我说过还有另一种方式来注入Mapper接口的代理实现类&＃xff0c;这种方式是比较推荐的&＃xff0c;步骤如下&＃xff1a;

1.首先删掉SqlMapConfig.xml配置文件&＃xff0c;没错&＃xff0c;这次可以不再需要Mybatis的配置文件了。

2.修改ApplicationContext.xml配置文件&＃xff0c;将Sql会话工厂内的指定mybatis核心配置文件的那个property去掉

3.将手动注入Mapper接口代理实现的配置去掉

4.使用包扫描的方式批量引入Mapper&＃xff08;重点&＃xff09;&＃xff0c;配置如下&＃xff1a;

<bean class&＃61;"org.mybatis.spring.mapper.MapperScannerConfigurer"><property name&＃61;"basePackage" value&＃61;"blog.csdn.net.mchenys.mapper"/>bean>


使用包扫描方式的好处就是可以避免频繁的修改Spring的配置文件&＃xff0c;以后有新的Mapper接口和mapper映射文件就直接在Mapper包中添加即可&＃xff0c;完整的Spring配置文件修改如下&＃xff1a;


<beans xmlns&＃61;"http://www.springframework.org/schema/beans"xmlns:context&＃61;"http://www.springframework.org/schema/context" xmlns:p&＃61;"http://www.springframework.org/schema/p"xmlns:aop&＃61;"http://www.springframework.org/schema/aop" xmlns:tx&＃61;"http://www.springframework.org/schema/tx"xmlns:xsi&＃61;"http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation&＃61;"http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsdhttp://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsdhttp://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd"><context:property-placeholder location&＃61;"classpath:db.properties" /><bean id&＃61;"dataSource" class&＃61;"org.apache.commons.dbcp.BasicDataSource"destroy-method&＃61;"close"><property name&＃61;"driverClassName" value&＃61;"${jdbc.driver}" /><property name&＃61;"url" value&＃61;"${jdbc.url}" /><property name&＃61;"username" value&＃61;"${jdbc.username}" /><property name&＃61;"password" value&＃61;"${jdbc.password}" /><property name&＃61;"maxActive" value&＃61;"10" /><property name&＃61;"maxIdle" value&＃61;"5" />bean><bean id&＃61;"sqlSessionFactory" class&＃61;"org.mybatis.spring.SqlSessionFactoryBean"><property name&＃61;"dataSource" ref&＃61;"dataSource">property>bean><bean class&＃61;"org.mybatis.spring.mapper.MapperScannerConfigurer"><property name&＃61;"basePackage" value&＃61;"blog.csdn.net.mchenys.mapper"/>bean>
beans>


删掉Mybatis配置文件后的工程结构如下&＃xff1a;

看起来就挺爽的&＃xff0c;少了一个配置文件&＃xff0c;执行测试类效果是一样的&＃xff0c;这里就不啰嗦了。