<bean id="xx" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
     <property name="order" value="http://www.mamicode.com/10" />
     <property name="ignoreUnresolvablePlaceholders" value="http://www.mamicode.com/true" />
     <property name="locations">
      <list>
       <value>classpath:xx.properties</value>
      </list>
     </property>
 </bean>