C3P0连接池+MySQL的配置及wait_timeout问题的解决方法

<c3p0-config>
< default-config>
<!--当连接池中的连接耗尽的时候c3p0一次同时获取的连接数。Default: 3 -->
<property name="acquireIncrement">3</property>
<!--定义在从数据库获取新连接失败后重复尝试的次数。Default: 30 --> 
< property name="acquireRetryAttempts">30</property>
<!--两次连接中间隔时间，单位毫秒。Default: 1000 --> 
< property name="acquireRetryDelay">1000</property>
<!--连接关闭时默认将所有未提交的操作回滚。Default: false --> 
< property name="autoCommitOnClose">false</property>
<!--c3p0将建一张名为Test的空表，并使用其自带的查询语句进行测试。如果定义了这个参数 那么
属性preferredTestQuery将被忽略。你不能在这张Test表上进行任何操作，它将只供c3p0测试
使用。Default: null-->
<property name="automaticTestTable">Test</property>
<!--获取连接失败将会引起所有等待连接池来获取连接的线程抛出异常。但是数据源仍有效
保留，并在下次调用getConnection()的时候继续尝试获取连接。如果设为true，那么在尝试
获取连接失败后该数据源将申明已断开并永久关闭。Default: false-->
<property name="breakAfterAcquireFailure">false</property>
<!--当连接池用完时客户端调用getConnection()后等待获取新连接的时间，超时后将 抛出
SQLException,如设为0则无限期等待。单位毫秒。Default: 0 -->
<property name="checkoutTimeout">100</property>
<!--通过实现ConnectionTester或QueryConnectionTester的 类来 测试连接。类名需制定全路径。
Default: com.mchange.v2.c3p0.impl.DefaultConnectionTester-->
<property name="connectionTesterClassName"></property>
<!--指定c3p0 libraries的路径，如果（通常都是这样）在本地即可获得那么无需设置，默认null即可
Default: null-->
<property name="factoryClassLocation">null</property>
<!--Strongly disrecommended. Setting this to true may lead to subtle and bizarre bugs.
（文档原文）作者强烈建议不使用的一个属性-->
<property name="forceIgnoreUnresolvedTransactions">false</property>
<!--每60秒检查所有连接池中的空闲连接。Default: 0 不检测 -->
<property name="idleConnectionTestPeriod">60</property>
<!--初始化时获取三个连接，取值应在minPoolSize与maxPoolSize之间。 Default: 3 -->
<property name="initialPoolSize">3</property>
<!--最大空闲时间,60秒内未使用则连接被丢弃。若为0则永不丢弃。Default: 0 -->
<property name="maxIdleTime">60</property>
<!--连接池中保留的最大连接数。Default: 15 -->
<property name="maxPoolSize">15</property>
<!--JDBC的标准参数，用以控制数据源内加载的PreparedStatements数量。但 由于预缓存的statements
属于单个connection而不是整个连接池。所以设置这个参数需要考虑到多方面的因素。
如果maxStatements与maxStatementsPerConnection均为0，则缓存被关闭。Default: 0-->
<property name="maxStatements">100</property>
<!--maxStatementsPerConnection定义了连接池内单个连接所 拥有的最大缓存statements数。Default: 0 -->
<property name="maxStatementsPerConnection"></property>
<!--c3p0是异步操作的，缓慢的JDBC操作通过帮助进程完成。扩展这些操作可以有效的提升性 能
通过多线程实现多个操作同时被执行。Default: 3--> 
< property name="numHelperThreads">3</property>
<!--当用户调用getConnection()时使root用户成为去获取连接的用户。主要用于 连接池连接非c3p0
的数据源时。Default: null-->
<property name="overrideDefaultUser">root</property>
<!--与overrideDefaultUser参数对应使用的一个参数。Default: null-->
<property name="overrideDefaultPassword">password</property>
<!--密码。Default: null-->
<property name="password"></property>
<!--定义所有连接测试都执行的测试语句。在使用连接测试的情况下这个一显著提高测试速度。注意：
测试的表必须在初始数据源的时候就存在。Default: null--> 
< property name="preferredTestQuery">select id from test where id=1</property>
<!--用户修改系统配置参数执行前最多等待300秒。Default: 300 -->
<property name="propertyCycle">300</property>
<!--因性能消耗大请只在需要的时候使用它。如果设为true那么在每个connection提交 的
时候都将校验其有效性。建议使用idleConnectionTestPeriod或automaticTestTable
等方法来提升连接测试的性能。Default: false -->
<property name="testConnectionOnCheckout">false</property>
<!--如果设为true那么在取得连接的同时将校验连接的有效性。Default: false -->
<property name="testConnectionOnCheckin">true</property>
<!--用户名。Default: null-->
<property name="user">root</property>
<!--早期的c3p0版本对JDBC接口采用动态反射代理。在早期版本用途广泛的情况下这个参数
允许用户恢复到动态反射代理以解决不稳定的故障。最新的非反射代理更快并且已经开始
广泛的被使用，所以这个参数未必有用。现在原先的动态反射与新的非反射代理同时受到
支持，但今后可能的版本可能不支持动态反射代理。Default: false-->
<property name="usesTraditionalReflectiveProxies">false</property>

<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"> 
<property name="driverClass" value="${jdbc.driver}"/> 
<property name="jdbcUrl" value="${jdbc.url}"/> 
<property name="user" value="${jdbc.user}"/> 
<property name="password" value="${jdbc.password}"/> 
</bean>

Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> 1hge26l9jv0ov961czeg8w|a2f51c, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1hge26l9jv0ov961czeg8w|a2f51c, idleConnectionTestPeriod -> 0, initialPoolSize -> 3, jdbcUrl -> jdbc:mysql://192.168.6.24:3306/ETeam, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 15, maxStatements -> 0, maxStatementsPerConnection -> 0, minPoolSize -> 3, numHelperThreads -> 3, numThreadsAwaitingCheckoutDefaultUser -> 0, preferredTestQuery -> null, properties -> {user=******, password=******}, propertyCycle -> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false ]

严重: Servlet.service() for servlet [ETeam] in context with path [/ETeam] threw exception [Request processing failed; nested exception is org.springframework.dao.RecoverableDataAccessException: 
### Error querying database. Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 55,518,630 milliseconds ago. The last packet sent successfully to the server was 55,518,631 milliseconds ago. 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. 
### The error may exist in com/mango/mapper/ProductMapper.java (best guess) 
### The error may involve defaultParameterMap 
### The error occurred while setting parameters 
### SQL: SELECT * FROM product 
### Cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 55,518,630 milliseconds ago. The last packet sent successfully to the server was 55,518,631 milliseconds ago. 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. 
; SQL []; The last packet successfully received from the server was 55,518,630 milliseconds ago. The last packet sent successfully to the server was 55,518,631 milliseconds ago. 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.; nested exception is com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 55,518,630 milliseconds ago. The last packet sent successfully to the server was 55,518,631 milliseconds ago. 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.] with root cause 
java.net.SocketException: Connection reset by peer: socket write error 
at java.net.SocketOutputStream.socketWrite0(Native Method) 
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:113) 
at java.net.SocketOutputStream.write(SocketOutputStream.java:159) 
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82) 
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140) 
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3634) 
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2460) 
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2625) 
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2551) 
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1861) 
at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1192) 
at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.execute(NewProxyPreparedStatement.java:989) 
at sun.reflect.GeneratedMethodAccessor46.invoke(Unknown Source) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
at java.lang.reflect.Method.invoke(Method.java:606) 
at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:62) 
at com.sun.proxy.$Proxy138.execute(Unknown Source) 
at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:59) 
at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:73) 
at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:60) 
at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:267) 
at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:137) 
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:96) 
at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:77) 
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:108) 
at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:102) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
at java.lang.reflect.Method.invoke(Method.java:606) 
at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:358) 
at com.sun.proxy.$Proxy357.selectList(Unknown Source) 
at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:198) 
at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:119) 
at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:63) 
at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52) 
at com.sun.proxy.$Proxy376.getProductIndex(Unknown Source) 
at com.mango.service.impl.ProductServiceImpl.getProductIndex(ProductServiceImpl.java:25) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
at java.lang.reflect.Method.invoke(Method.java:606) 
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) 
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99) 
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:280) 
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) 
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) 
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) 
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213) 
at com.sun.proxy.$Proxy377.getProductIndex(Unknown Source) 
at com.mango.controller.PageController.index(PageController.java:57) 
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) 
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
at java.lang.reflect.Method.invoke(Method.java:606) 
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) 
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) 
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) 
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:814) 
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:737) 
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) 
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) 
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) 
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:969) 
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:860) 
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621) 
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845) 
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305) 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
at com.mango.filter.BaseFilter.doFilter(BaseFilter.java:34) 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:317) 
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127) 
at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:115) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:137) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:169) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:63) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilterInternal(BasicAuthenticationFilter.java:158) 
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:200) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:121) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:66) 
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56) 
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.session.ConcurrentSessionFilter.doFilter(ConcurrentSessionFilter.java:134) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105) 
at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331) 
at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:214) 
at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:177) 
at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346) 
at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262) 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
at org.sitemesh.webapp.contentfilter.ContentBufferingFilter.bufferAndPostProcess(ContentBufferingFilter.java:169) 
at org.sitemesh.webapp.contentfilter.ContentBufferingFilter.doFilter(ContentBufferingFilter.java:126) 
at org.sitemesh.webapp.SiteMeshFilter.doFilter(SiteMeshFilter.java:120) 
at org.sitemesh.config.ConfigurableSiteMeshFilter.doFilter(ConfigurableSiteMeshFilter.java:163) 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) 
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) 
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) 
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222) 
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123) 
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) 
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168) 
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99) 
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929) 
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) 
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) 
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002) 
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585) 
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1813) 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) 
at java.lang.Thread.run(Thread.java:745)

The last packet successfully received from the server was 55,518,630 milliseconds ago. The last packet sent successfully to the server was 55,518,631 milliseconds ago. 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.; nested exception is com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 55,518,630 milliseconds ago. The last packet sent successfully to the server was 55,518,631 milliseconds ago. 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.] with root cause

mysql> show global variables like 'wait_timeout';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wait_timeout | 28800 |
+---------------+-------+
1 row in set

<!--每5小时检查所有连接池中的空闲连接。防止mysql wait_timeout（默认的为8小时） --> 
<property name="idleConnectionTestPeriod" value="18000"/>

// this is run by a single-threaded timer, so we don't have 
// to worry about multiple threads executing the task at the same 
// time 
class CheckIdleResourcesTask extends TimerTask 
{ 
public void run() 
{ 
try 
{ 
//System.err.println("c3p0-JENNIFER: refurbishing idle resources - " + new Date() + " [" + BasicResourcePool.this + "]"); 
if (Debug.DEBUG && Debug.TRACE >= Debug.TRACE_MED && logger.isLoggable(MLevel.FINER)) 
logger.log(MLevel.FINER, "Refurbishing idle resources - " + new Date() + " [" + BasicResourcePool.this + "]"); 
synchronized ( BasicResourcePool.this ) 
{ checkIdleResources(); } 
} 
catch ( ResourceClosedException e ) // one of our async threads died 
{ 
//e.printStackTrace(); 
if ( Debug.DEBUG ) 
{ 
if ( logger.isLoggable( MLevel.FINE ) ) 
logger.log( MLevel.FINE, "a resource pool async thread died.", e ); 
} 
unexpectedBreak(); 
} 
} 
}

private void testPooledConnection(Object resc) throws Exception 
{ 
PooledConnection pc = (PooledConnection) resc; 
Throwable[] throwableHolder = EMPTY_THROWABLE_HOLDER; 
int status; 
Connection conn = null; 
Throwable rootCause = null; 
try 
{ 
//we don't want any callbacks while we're testing the resource 
pc.removeConnectionEventListener( cl ); 
conn = pc.getConnection(); //checkout proxy connection 
// if this is a c3p0 pooled-connection, let's get underneath the 
// proxy wrapper, and test the physical connection sometimes. 
// this is faster, when the testQuery would not otherwise be cached, 
// and it avoids a potential statusOnException() double-check by the 
// PooledConnection implementation should the test query provoke an 
// Exception 
Connection testConn; 
if (scache != null) //when there is a statement cache... 
{ 
// if it's the slow, default query, faster to test the raw Connection 
if (testQuery == null && connectionTesterIsDefault && c3p0PooledConnections) 
testConn = ((AbstractC3P0PooledConnection) pc).getPhysicalConnection(); 
else //test will likely be faster on the proxied Connection, because the test query is probably cached 
testConn = conn; 
} 
else //where there's no statement cache, better to use the physical connection, if we can get it 
{ 
if (c3p0PooledConnections) 
testConn = ((AbstractC3P0PooledConnection) pc).getPhysicalConnection(); 
else 
testConn = conn; 
} 
if ( testQuery == null ) 
status = connectionTester.activeCheckConnection( testConn ); 
else 
{ 
if (connectionTester instanceof UnifiedConnectionTester) 
{ 
throwableHolder = thp.getThrowableHolder(); 
status = ((UnifiedConnectionTester) connectionTester).activeCheckConnection( testConn, testQuery, throwableHolder ); 
} 
else if (connectionTester instanceof QueryConnectionTester) 
status = ((QueryConnectionTester) connectionTester).activeCheckConnection( testConn, testQuery ); 
else 
{ 
// System.err.println("[c3p0] WARNING: testQuery '" + testQuery + 
// "' ignored. Please set a ConnectionTester that implements " + 
// "com.mchange.v2.c3p0.advanced.QueryConnectionTester, or use the " + 
// "DefaultConnectionTester, to test with the testQuery."); 
logger.warning("[c3p0] testQuery '" + testQuery + 
"' ignored. Please set a ConnectionTester that implements " + 
"com.mchange.v2.c3p0.QueryConnectionTester, or use the " + 
"DefaultConnectionTester, to test with the testQuery."); 
status = connectionTester.activeCheckConnection( testConn ); 
} 
} 
} 
catch (Exception e) 
{ 
if (Debug.DEBUG) 
logger.log(MLevel.FINE, "A Connection test failed with an Exception.", e); 
//e.printStackTrace(); 
status = ConnectionTester.CONNECTION_IS_INVALID; 
// System.err.println("rootCause ------>"); 
// e.printStackTrace(); 
rootCause = e; 
} 
finally 
{ 
if (rootCause == null) 
rootCause = throwableHolder[0]; 
else if (throwableHolder[0] != null && logger.isLoggable(MLevel.FINE)) 
logger.log(MLevel.FINE, "Internal Connection Test Exception", throwableHolder[0]); 
if (throwableHolder != EMPTY_THROWABLE_HOLDER) 
thp.returnThrowableHolder( throwableHolder ); 
ConnectionUtils.attemptClose( conn ); //invalidate proxy connection 
pc.addConnectionEventListener( cl ); //should we move this to CONNECTION_IS_OKAY case"Connection is invalid"); 
else 
throwMe = SqlUtils.toSQLException("Connection is invalid", rootCause); 
throw throwMe; 
default: 
throw new Error("Bad Connection Tester (" + 
connectionTester + ") " + 
"returned invalid status (" + status + ")."); 
} 
}