spring properties有关问题，

spring properties问题，急~~~
用spring读取properties，出错：
dataSource_config.xml:
<bean id="propertyPlaceHolderConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>file:conf/DB.properties</value>
</list>
</property>
<property name="fileEncoding">
<value>GBK</value>
</property>
</bean>
<bean id="dataSource" lazy-init="true" destroy-method="close"
class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="driverClass" value="${it.db.driverClass}"></property>
<property name="jdbcUrl" value="${it.db.jdbcUrl}"></property>
<property name="user" value="${it.db.userName}"></property>
<property name="password" value="${it.db.password}"></property>
<property name="maxIdleTime" value="60"></property>
<property name="idleConnectionTestPeriod" value="60"></property>
</bean>

DB.properties文件:
it.db.jdbcUrl=jdbc:oracle:thin:@192.168.35.207:1521:orcl
it.db.driverClass=oracle.jdbc.driver.OracleDriver
it.db.userName=cnmscfg
it.db.password=ffcsoss

报错信息如下：
Exception in thread "main" org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean definition with name 'dataSource' defined in file [G:\MyWorkSpace\ITResourceManager\conf\dataSource_config.xml]: Could not resolve placeholder 'it.db.driverClass'

驱动包什么的都加了，没用properies之前测试过，可以运行，加了之后就出错了，求高手解决

------解决方案--------------------
是这么做的啊。
看看文件在不在指定的地方，如果启动的时候没报错，可能在指定的地方有别的DB.properties文件在那儿。
------解决方案--------------------

XML code

<bean id="dataSource" lazy-init="true" destroy-method="close"class="com.mchange.v2.c3p0.ComboPooledDataSource"><property name="driverClass" value="${it.db.driverClass}"></property><property name="jdbcUrl" value="${it.db.jdbcUrl}"></property><property name="user" value="${it.db.userName}"></property><property name="password" value="${it.db.password}"></property><property name="maxIdleTime" value="60"></property><property name="idleConnectionTestPeriod" value="60"></property></bean>