关于数据库You can't perform any operations on this connection的错误

              最近应用老是运行到一段时间就垮掉，查看日志 发现报错如下：

                  You can't perform any operations on this connection. It has been automatically closed by Proxool for some reason (see logs).  在网上查询是可能查询时间过长，导致数据链接被回收不可用，因此要修改数据库配置maximum-active-time参数，关于其默认值见http://proxool.sourceforge.net/properties.html，及http://proxool.sourceforge.net/api-dev/org/logicalcobwebs/proxool/configuration/PropertyConfigurator.html，下面是proxool配置文件如下：

     <bean id="dataSource"
class="org.logicalcobwebs.proxool.ProxoolDataSource" destroy-method="reset">
<property name="driver">
<value>${jdbc.driver}</value>
</property>
<property name="driverUrl">
<value>${jdbc.url}</value>
</property>
<property name="user">
<value>${jdbc.username}</value>
</property>
<property name="password">
<value>${jdbc.password}</value>
</property>
<property name="houseKeepingTestSql">
<value>select sysdate from DUAL</value>
</property>
<property name="testBeforeUse">
<value>false</value>
</property>
<property name="maximumConnectionCount">
<value>60</value>
</property>
   <property name="minimumConnectionCount">
     <value>20</value>
   </property>
<property name="delegateProperties">
<value>
user=${jdbc.username},password=${jdbc.password}
</value>
</property>
<property name="simultaneousBuildThrottle">
<value>10</value>
</property>
<property name="maximumActiveTime"><value>900000</value></property>

<！自动侦擦各个连接的状态时间间隔(单位毫秒)侦擦到空闲的连接马上回收，超时毁，默认30秒－－>

<property name="houseKeepingSleepTime"><value>20000</value></property>
</bean>