hibernate 使用连接池连接数据库时 自动断开处理

项目中使用c3p0连接数据库里 ,每隔一段时间就报以下错误:

JDBC begin failed [ERROR] 2011-05-08 01:56:33
com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 
** BEGIN NESTED EXCEPTION ** 
java.net.SocketException
MESSAGE: Connection timed out
STACKTRACE:
java.net.SocketException: Connection timed out
	at java.net.SocketOutputStream.socketWrite0(Native Method)
	at java.net.SocketOutputStream.socketWrite(Unknown Source)
	at java.net.SocketOutputStream.write(Unknown Source)
	at java.io.BufferedOutputStream.flushBuffer(Unknown Source)

..................

	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
	at java.lang.Thread.run(Unknown Source)
Caused by: org.hibernate.TransactionException: JDBC begin failed: 
	at org.hibernate.transaction.JDBCTransaction.begin(JDBCTransaction.java:68)
	at org.hibernate.impl.SessionImpl.beginTransaction(SessionImpl.java:1326)
	at org.springframework.orm.hibernate3.HibernateTransactionManager.doBegin(HibernateTransactionManager.java:558)
	... 89 more
Caused by: com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: 

错误内容太多 ,中间省略很大一部分..

datasource配置:

	<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
		destroy-method="close">
		<property name="driverClass" value="com.mysql.jdbc.Driver">
		</property>
		<property name="minPoolSize" value="20"></property>
		<property name="initialPoolSize" value="25"></property>
		<property name="maxPoolSize" value="100"></property>
		<property name="maxStatements" value="200"></property>
		<property name="maxStatementsPerConnection" value="200"></property>
		<property name="acquireIncrement" value="3"></property>
		<property name="acquireRetryAttempts" value="10"></property>
		<property name="autoCommitOnClose" value="false"></property>
		<property name="acquireRetryDelay" value="2000"></property>
		<property name="maxIdleTimeExcessConnections" value="50"></property>
		<property name="maxIdleTime" value="86400000"></property>
		<property name="automaticTestTable" value="c3p0_test"></property>
		<property name="breakAfterAcquireFailure" value="false"></property>
		<property name="jdbcUrl"
			value="${jdbc.url}?setUnicode=true&characterEncoding=utf8">
		</property>
		<property name="user" value="${jdbc.username}"></property>
		<property name="password" value="${jdbc.password}"></property>
	</bean>

几经周折,发现使用的mysql数据库有一个系统参数为

wait-timeout The number of seconds the server waits for activity on a noninteractive connection before closing it.

看网上说的默认时间是8小时(但是我使用的mysql版本配置文件中没有发现有此属性配置,也不知道默认的是不是8小时,姑且当作是),所以在连接池配置中添加了以下配置不再出现异常:

<property name="idleConnectionTestPeriod" value="60"></property>

注意此时间要小于数据库配置的空闲等待时间