hibernate + c3p0连接池 出现以下错误，求解答！

Question

05-Apr-2016 10:36:43.186 INFO [C3P0PooledConnectionPoolManager[identityToken->2sbh7t9f1rc58zmz5ikx9|52feca18]-AdminTaskTimer] org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading Illegal access: this web application instance has been stopped already. Could not load [com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1354)
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1340)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1205)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1166)
at com.mchange.v2.resourcepool.BasicResourcePool.checkIdleResources(BasicResourcePool.java:1584)
at com.mchange.v2.resourcepool.BasicResourcePool.access$2000(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$CheckIdleResourcesTask.run(BasicResourcePool.java:2116)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)

Exception in thread "C3P0PooledConnectionPoolManager[identityToken->2sbh7t9f1rc58zmz5ikx9|52feca18]-AdminTaskTimer" java.lang.IllegalStateException: Can't overwrite cause with java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [com.mchange.v2.resourcepool.BasicResourcePool$AsyncTestIdleResourceTask]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
at java.lang.Throwable.initCause(Throwable.java:457)
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1343)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1205)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1166)
at com.mchange.v2.resourcepool.BasicResourcePool.checkIdleResources(BasicResourcePool.java:1584)
at com.mchange.v2.resourcepool.BasicResourcePool.access$2000(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$CheckIdleResourcesTask.run(BasicResourcePool.java:2116)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)
Caused by: java.lang.ClassNotFoundException
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1342)
... 7 more
1、此错误会不定时出现。
2、hibernate版本是4.3.5，Struts2版本是2.3.24.1；并没有使用spring...
3、出现此错误时，CRUD功能正常！
在网上找了两天资料，没找到正确的解决方法，求大神解答！谢谢

Answer 1

    c3p0连接池的配置如下：
            <property name="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property>
    <property name="hibernate.c3p0.max_size">20</property>
    <property name="hibernate.c3p0.min_size">5</property>
    <property name="hibernate.c3p0.timeout">120</property>
    <property name="automaticTestTable">Test</property>
    <property name="hibernate.c3p0.max_statements">100</property>
    <property name="hibernate.c3p0.idle_test_period">120</property>
    <property name="hibernate.c3p0.acquire_increment">1</property>
    <property name="c3p0.testConnectionOnCheckout">true</property>
    <property name="c3p0.idleConnectionTestPeriod">18000</property>
    <property name="c3p0.maxIdleTime">25000</property>
    <property name="c3p0.idle_test_period">120</property>