mybatis與Spring三種開發方式詳解（二）Mapper動態代理開發

之前我們說到傳統的dao層開發，今天我們來談談第二種mybatis與Spring的開發方式，Mapper動態代理開發。

首先這裡上一波@test測試程式碼，大家先看一下mybatis測試的完整的過程程式碼，以便後面的講解。

public class MybatisMapperTest {

    @Test
    public void testMapper() throws Exception {
        //載入核心配置檔案
        String resource = "sqlMapConfig.xml"
 
;
        InputStream in = Resources.getResourceAsStream(resource);
        //建立SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        //建立SqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //SqlSEssion幫我生成一個實現類  （給介面）
 

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);


        User user = userMapper.findUserById(10);
        System.out.println(user);
    }

1.編寫Mapper.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.itheima.mybatis.mapper.UserMapper">


    <!-- 通過ID查詢一個使用者 -->
    <select id="findUserById" parameterType="Integer" resultType="User">
        select * from user where id = #{v} <!-- 寫什麼都行，寫個abc也行 -->
    </select>
</mapper>

2.實現UserMapper介面

package com.itheima.mybatis.mapper;
import com.itheima.mybatis.pojo.User;

public interface UserMapper {

    public User findUserById(Integer id);

}

3.配置Spring核心檔案applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
    http://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.xsd
    http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd">


    <context:property-placeholder location="classpath:db.properties"/>

    <!-- 資料庫連線池 -->
    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
        destroy-method="close">
        <property name="driverClassName" value="${jdbc.driver}" />
        <property name="url" value="${jdbc.url}" />
        <property name="username" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />
        <property name="maxActive" value="10" />
        <property name="maxIdle" value="5" />
    </bean>

    <!-- Mybatis的工廠 -->
    <bean id="sqlSessionFactoryBean" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!-- 核心配置檔案的位置 -->
        <property name="configLocation" value="classpath:sqlMapConfig.xml"/>
    </bean>

    <!-- Mapper動態代理開發 -->
    <bean id="userMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
        <property name="sqlSessionFactory" ref="sqlSessionFactoryBean"/>
        <property name="mapperInterface" value="com.itheima.mybatis.mapper.UserMapper"/>
    </bean>
</beans>

注意這塊配置，生成我們定義的UserMapper介面的實現類

<bean id="userMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
        <property name="sqlSessionFactory" ref="sqlSessionFactoryBean"/>
        <property name="mapperInterface" value="com.itheima.mybatis.mapper.UserMapper"/>
    </bean>
</beans>

這裡對應的就是我們一開始完整的@test程式碼的如下程式碼，這個過程：

SqlSession sqlSession = sqlSessionFactory.openSession();

//SqlSEssion幫我生成一個實現類  （給介面）
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

配置檔案中注入的mapperInterface屬性就是對應getMapper(UserMapper.class)中的引數。
3.Mapper配置檔案UserMapper.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.itheima.mybatis.mapper.UserMapper">


    <!-- 通過ID查詢一個使用者 -->
    <select id="findUserById" parameterType="Integer" resultType="User">
        select * from user where id = #{v} <!-- 寫什麼都行，寫個abc也行 -->
    </select>
</mapper>

4.mybatis核心配置檔案sqlMapConfig.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>
    <!-- 設定別名 -->
    <typeAliases>
        <!-- 2. 指定掃描包，會把包內所有的類都設定別名，別名的名稱就是類名，大小寫不敏感 -->
        <package name="com.itheima.mybatis.pojo" />
    </typeAliases>
    <mappers>
        <package name="com.itheima.mybatis.mapper"/>
    </mappers>

</configuration>

[email protected]測試類junitTest.java

package com.itheima.mybatis.junit;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.itheima.mybatis.mapper.UserMapper;
import com.itheima.mybatis.pojo.User;

public class JunitTest {


    @Test
    public void testMapper() throws Exception {
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserMapper mapper = ac.getBean(UserMapper.class);
//      UserMapper mapper = (UserMapper) ac.getBean("userMapper");
        User user = mapper.findUserById(10);
        System.out.println(user);
    }
}

這就是第二種mybatis與Spring開發方式，Mapper動態代理開發。

mybatis與Spring三種開發方式詳解（三）Mapper動態代理掃描包形式開發dao（增強第二種方式）

只需把Spring核心配置檔案applicationContext.xml中改為如下程式碼即可：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
    http://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.xsd
    http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd">


    <context:property-placeholder location="classpath:db.properties"/>

    <!-- 資料庫連線池 -->
    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
        destroy-method="close">
        <property name="driverClassName" value="${jdbc.driver}" />
        <property name="url" value="${jdbc.url}" />
        <property name="username" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />
        <property name="maxActive" value="10" />
        <property name="maxIdle" value="5" />
    </bean>

    <!-- Mybatis的工廠 -->
    <bean id="sqlSessionFactoryBean" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!-- 核心配置檔案的位置 -->
        <property name="configLocation" value="classpath:sqlMapConfig.xml"/>
    </bean>

    <!-- Mapper動態代理開發   掃描 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <!-- 基本包 -->
        <property name="basePackage" value="com.itheima.mybatis.mapper"/>
    </bean>

新增後我們便不用去書寫複雜的注入配置程式碼，因為MapperScannerConfigurer會自動去尋找basePackage即com.itheima.mybatis.mapper下的子包及其子包中的檔案，以後開發用這種最多。