mybatis--MapperScannerConfigurer

一般我們這樣配置

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"
      lazy-init="false">
    <property name="dataSource" ref="dataSource"/>
    <property name="mapperLocations" value="classpath:sqlmapper/*Mapper.xml"/>
    <property name="plugins">
        <list>
            <bean class="***">
                <property name="dialect">
                    <bean class="***"/>
                </property>
            </bean>
        </list>
    </property>
</bean>

<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="*.*.*" />
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />
    </bean>

內部使用 ClassPathMapperScanner 來掃描包下面的mapper接口，每個接口構建一個BeanDefinitionHolder（beanclass為MapperFactoryBean）

當需要mapperinterface實例時，由MapperFactoryBean工廠產生

public T getObject() throws Exception {
        return this.getSqlSession().getMapper(this.mapperInterface);
    }

可以吧this.getSqlSession()看做是sqlSessionFactory的封裝SqlSessionTemplate，實際調用

public <T> T getMapper(Class<T> type) {
    return this.getConfiguration().getMapper(type, this);
}

這里的this.getConfiguration()實際是

return this.sqlSessionFactory.getConfiguration();

 

走到這步，就必須來看SqlSessionFactoryBean做了什么吧？關鍵方法如下：

protected SqlSessionFactory buildSqlSessionFactory() throws IOException {
    XMLConfigBuilder xmlConfigBuilder = null;
    Configuration configuration;
    ..................
     if(this.transactionFactory == null) {
            this.transactionFactory = new SpringManagedTransactionFactory();
     }

     Environment var29 = new Environment(this.environment, this.transactionFactory, this.dataSource); configuration.setEnvironment(var29);
　　　...............       

        if(!ObjectUtils.isEmpty(this.mapperLocations)) {
           XMLMapperBuilder e = new XMLMapperBuilder(var33.getInputStream(), configuration, var33.toString(), configuration.getSqlFragments());
           e.parse();
        }
        return this.sqlSessionFactoryBuilder.build(configuration);
}

紅色部分，設置configuration->environment->springManagedTransactionFactory

XMLMapperBuilder 詳細過程見 mybatis緩存創建過程 ，parse中xml的namespace相應的class注冊給configuration

public <T> void addMapper(Class<T> type) {
    this.mapperRegistry.addMapper(type);
}

最后的return調用 SqlSessionFactoryBuilder

public SqlSessionFactory build(Configuration config) {
    return new DefaultSqlSessionFactory(config);
}

這里的Configuration對象很關鍵

 

總結如下：org.mybatis.spring.SqlSessionFactoryBean解析mapper xml配置，根據namespace添加class mapper組裝Configuration對象，包裝為DefaultSqlSessionFactory；

org.mybatis.spring.mapper.MapperScannerConfigurer掃描basePackage下的mapper接口，封裝為MapperFactoryBean注冊給spring容器，當調用"mapper接口"時去DefaultSqlSessionFactory-》Configuration獲得接口類的代理類

MapperProxy mapperProxy = new MapperProxy(sqlSession, this.mapperInterface, this.methodCache);

進一步的調用過程見 mybatis緩存

 

如何在調用中事務起作用，見下篇