Mysql服务器默认的“wait_timeout”是8小时，也就是说一个connection空闲超过8个小时，Mysql将自动断开该 connection。connections如果空闲超过8小时，Mysql将其断开，而DBCP并不知道该connection已经失效，如果这时有 Client请求connection，DBCP将该失效的Connection提供给Client，将会造成上面的异常。
        mysql配置中my.cnf 的wait_timeout值一定要大于等于连接池种的idle_timeout 值。否则mysql会在wait_timeout的时间后关闭连接，然而连接池还认为该连接可用，这样就会产生异常。 
System Runtime Error:

Could not open Hibernate Session for transaction; nested exception is org.hibernate.TransactionException: JDBC begin failed:

javax.servlet.ServletException: Could not open Hibernate Session for transaction; nested exception is org.hibernate.TransactionException: JDBC begin failed: at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:515) at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:75) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.buptnu.usermanage.filter.LoginFilter.doFilterInternal(LoginFilter.java:58) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:75) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148) at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:199) at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:282) at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:767) at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:697) at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:889) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684) at java.lang.Thread.run(Thread.java:595)

DBCP连接池说明:
driverClassName 
url 
username 
password 
上面四个分别是驱动,连接字符串,用户名和密码

maxActive 连接池支持的最大连接数 
maxIdle 连接池中最多可空闲maxIdle个连接 
minIdle 连接池中最少空闲maxIdle个连接 
initialSize 初始化连接数目 
maxWait 连接池中连接用完时,新的请求等待时间,毫秒 
timeBetweenEvictionRunsMillis和minEvictableIdleTimeMillis一起使用,每 

timeBetweenEvictionRunsMillis毫秒秒检查一次连接池中空闲的连接,把空闲时间超过minEvictableIdleTimeMillis毫秒的连接断开,直到连接池中的连接数到minIdle为止

主要把这两个参数加上就好。

minEvictableIdleTimeMillis 连接池中连接可空闲的时间,毫秒

removeAbandoned true,false,是否清理removeAbandonedTimeout秒没有使用的活动连接,清理后并没有放回连接池 
removeAbandonedTimeout 活动连接的最大空闲时间 
logAbandoned true,false,连接池收回空闲的活动连接时是否打印消息 
minEvictableIdleTimeMillis, removeAbandonedTimeout这两个参数针对的连接对象不样,minEvictableIdleTimeMillis针对连接池中的连接 对象,removeAbandonedTimeout针对未被close的活动连接