在XML文件中读取属性文件（.properties）中的元素值：
web.xml
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/conf/dataAccessContext.xml</param-value>
</context-param>
<listener>
<listener-class>
org.springframework.web.context.ContextLoaderListener
</listener-class>
</listener>
dataAccessContext.xml
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<list>
<value>/WEB-INF/conf/proxool-jdbc.properties</value>
</list>
</property>
</bean>
<bean id="dataSource" class="org.logicalcobwebs.proxool.ProxoolDataSource" autowire="byName">
<property name="driver">
<value>${proxool.driver}</value>
</property>
<property name="driverUrl">
<value>${proxool.url}</value>
</property>
<property name="user">
<value>${proxool.username}</value>
</property>
<property name="password">
<value>${proxool.password}</value>
</property>
<property name="alias">
<value>${proxool.alias}</value>
</property>
<property name="houseKeepingSleepTime">
<value>90000</value>
</property>
</bean>
proxool-jdbc.properties
proxool.driver=org.gjt.mm.mysql.Driver
proxool.username=xx
proxool.password=xx
proxool.url=jdbc:mysql://localhost:3306/xxx?useUnicode=true&characterEncoding=utf8&user=xx&password=xx
proxool.alias=xxx
