org.apache.commons.dbcp.SQLNestedException: Cannot load JDBC driver class

转载自：http://songjianyong.iteye.com/blog/1663170

org.springframework.transaction.CannotCreateTransactionException: Could not open JDBC Connection for transaction; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot load JDBC driver class '${jdbc.driverClassName}'
    at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:240)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.getTransaction(AbstractPlatformTransactionManager.java:371)
    at org.springframework.test.context.transaction.TransactionalTestExecutionListener$TransactionContext.startTransaction(TransactionalTestExecutionListener.java:513)
    at org.springframework.test.context.transaction.TransactionalTestExecutionListener.startNewTransaction(TransactionalTestExecutionListener.java:271)
    at org.springframework.test.context.transaction.TransactionalTestExecutionListener.beforeTestMethod(TransactionalTestExecutionListener.java:164)
    at org.springframework.test.context.TestContextManager.beforeTestMethod(TestContextManager.java:358)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:73)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: org.apache.commons.dbcp.SQLNestedException: Cannot load JDBC driver class '${jdbc.driverClassName}'
    at org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1429)
    at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1371)
    at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
    at org.springframework.jdbc.datasource.DataSourceTransactionManager.doBegin(DataSourceTransactionManager.java:202)
    ... 25 more
Caused by: java.lang.ClassNotFoundException: ${jdbc.driverClassName}
    at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
    at org.apache.commons.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1420)
    ... 28 more

在spring里使用org.mybatis.spring.mapper.MapperScannerConfigurer 进行自动扫描的时候，设置了sqlSessionFactory 的话，可能会导致PropertyPlaceholderConfigurer失效，也就是用${jdbc.username}这样之类的表达式，将无法获取到properties文件里的内容。 导致这一原因是因为，MapperScannerConigurer实际是在解析加载bean定义阶段的，这个时候要是设置sqlSessionFactory的话，会导致提前初始化一些类，这个时候，PropertyPlaceholderConfigurer还没来得及替换定义中的变量，导致把表达式当作字符串复制了。 但如果不设置sqlSessionFactory 属性的话，就必须要保证sessionFactory在spring中名称一定要是sqlSessionFactory ，否则就无法自动注入。又或者直接定义 MapperFactoryBean ，再或者放弃自动代理接口方式。

就是这个org.mybatis.spring.mapper.MapperScannerConfigurer中配置的bean下有属性sqlSessionFactory，如果配置了，就去掉这个属性，变成如下：

<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">

    <property value="com.hyq.showcase.mapper,com.hyq.common.core.mapper"
        name="basePackage" />

</bean>

以上的解决方案比较一般，在3.1.1版本中配置的时候提供了以下：

<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">

    <property name="basePackage" value="com.xxxx.dal.mapper" />

    <property name="sqlSessionFactoryBeanName" value="ysSqlSessionFactory" />

    <!-- <property name="sqlSessionFactory" ref="ysSqlSessionFactory"></property> -->

</bean>

改用sqlSessionFactoryBeanName注入就没有问题(不要使用sqlSessionFactory属性注入，使用sqlSessionFactoryBeanName注入)，因为这时不会立即初始化sqlSessionFactory,传入的只是名字，非bean，所以不会引发提前初始化问题。。 
以上供参考!