c3p0 + hibernate 的问题，头痛了快1个月了！

Question

小弟初学hibernate,用c3p0，一般运行都好，可是不定时 (有时候好几天都没事,有时候一个睡一晚上起来) 就出现了以下的错误：

Dec 25, 2008 3:41:13 PM com.mchange.v2.c3p0.stmt.GooGooStatementCache checkinStatement

INFO: Problem with checked-in Statement, discarding.

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: No operations allowed after statement closed.

    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)

    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)

    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)

    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)

    at com.mysql.jdbc.Util.getInstance(Util.java:381)

    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:984)

    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)

    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)

    at com.mysql.jdbc.StatementImpl.checkClosed(StatementImpl.java:380)

    at com.mysql.jdbc.PreparedStatement.clearParameters(PreparedStatement.java:784)

    at com.mchange.v2.c3p0.stmt.GooGooStatementCache.refreshStatement(GooGooStatementCache.java:604)

    at com.mchange.v2.c3p0.stmt.GooGooStatementCache.checkinStatement(GooGooStatementCache.java:236)

    at com.mchange.v2.c3p0.impl.NewPooledConnection.checkinStatement(NewPooledConnection.java:282)

    at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.close(NewProxyPreparedStatement.java:1807)

    at org.hibernate.jdbc.AbstractBatcher.closePreparedStatement(AbstractBatcher.java:534)

    at org.hibernate.jdbc.AbstractBatcher.closeStatement(AbstractBatcher.java:269)

    at org.hibernate.id.insert.AbstractReturningDelegate.releaseStatement(AbstractReturningDelegate.java:58)

    at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:36)

    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2158)

    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2638)

    at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:48)

    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:250)

    at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:298)

    at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:181)

    at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:107)

    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:187)

    at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)

    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:172)

    at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)

    at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)

    at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:535)

    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:523)

    at org.hibernate.impl.SessionImpl.save(SessionImpl.java:519)

    at com.icait.factory.HibernateUtil.add(HibernateUtil.java:18)

    at com.icait.dao.SubscriberDAOImpl.addSubscriber(SubscriberDAOImpl.java:19)

    at com.icait.action.SubscriberAddAction.execute(SubscriberAddAction.java:64)

    at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)

    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)

    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)

    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)

    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)

    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)

    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)

    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)

    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)

    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)

    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)

    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)

    at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)

    at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:283)

    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:690)

    at java.lang.Thread.run(Thread.java:619)

Dec 25, 2008 3:41:14 PM org.hibernate.util.JDBCExceptionReporter logExceptions

WARNING: SQL Error: 0, SQLState: 08S01

Dec 25, 2008 3:41:14 PM org.hibernate.util.JDBCExceptionReporter logExceptions

SEVERE: The last packet successfully received from the server was144382 seconds ago.The last packet sent successfully to the server was 144382 seconds ago, which  is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.

Dec 25, 2008 3:41:14 PM org.apache.struts.action.RequestProcessor processException

WARNING: Unhandled Exception thrown: class org.hibernate.exception.JDBCConnectionException

hibernate 配置如下：

<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">false</property>

  <property name="c3p0.idleConnectionTestPeriod">18000</property>


  <property name="c3p0.maxIdleTime">25000</property> 

    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>

    <property name="hibernate.connection.url">jdbc:mysql://localhost/conference</property>

    <property name="hibernate.connection.username">****</property>

    <property name="hibernate.connection.password">****</property>

    <property name="hibernate.show_sql">true</property>

    <property name="hibernate.current_session_context_class">thread</property>

google百度了头都大了，还是不知道什么地方有毛病，各位大虾看看配置什么的有什么不对啊?

Answer 1

“SEVERE: The last packet successfully received from the server was144382 seconds ago.The last packet sent successfully to the server was 144382 seconds ago, which is longer than the server configured value of 'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, or using the Connector/J connection property 'autoReconnect=true' to avoid this problem.”
你的log里说的很清楚了。原因是Mysql服务器默认的“wait_timeout”是8小时，如果一个connection空闲超过8个小时，Mysql将自动断开该 connection，而C3P0并不知道该connection已经失效，如果这时请求connection，将会造成上面的异常。你每次使用前判断connection是否有效就会避免这种异常。

解决的方法有3种：

增加wait_timeout的时间。
减少Connection pools中connection的lifetime。
测试Connection pools中connection的有效性。
当然最好的办法是同时综合使用上述3种方法，下面举个例子，假设wait_timeout为默认的8小时

C3P0增加以下配置信息:

//获取connnection时测试是否有效
testConnectionOnCheckin = true
//自动测试的table名称

automaticTestTable=C3P0TestTable

//set to something much less than wait_timeout, prevents connections from going stale
idleConnectionTestPeriod = 18000
//set to something slightly less than wait_timeout, preventing 'stale' connections from being handed out
maxIdleTime = 25000
//if you can take the performance 'hit', set to "true"
testConnectionOnCheckout = true