spring Cannot load JDBC driver class '${DRIVER}' 问题

<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"
          p:sqlSessionFactory-ref="sqlSessionFactory"
          p:basePackage="hx.nan.dao"/>

由于MaperScannerConfigrer会提前初始化sqlSessionFactory而还在没有加载配置文件时将配置的数据源加载，修改如下即可解决

<pre name="code" class="html"><bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"
          p:sqlSessionFactoryBeanName="sqlSessionFactory"
          p:basePackage="hx.nan.dao"/>