MySQL+Hibernate下连接空闲8小时自动断开问题解决方案

　前段时间刚完成一个家教网项目，数据库为MySQL5.0，持久层使用Hibernate 3.1，没有使用额外的连接池，那么Hibernate会默认使用它自带的一个默认连接池，也就是DriverManagerConnectionProvider。

　　先在本机上调试都毫无问题，于是部署到服务器上，也都没什么问题。由于这是新网站，根本还没正式对外发布和宣传，所以头两天根本没人访问。等到第二天，我再次访问网站时，问题就出现了，错误信息如下：

root cause

javax.servlet.ServletException: org.hibernate.exception.JDBCConnectionException: could not execute query org.apache.struts.action.RequestProcessor.processException(RequestProcessor.java:535) org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:433) org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236) org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196) org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414) javax.servlet.http.HttpServlet.service(HttpServlet.java:690) javax.servlet.http.HttpServlet.service(HttpServlet.java:803) org.apache.jsp.index_jsp._jspService(index_jsp.java:57) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:803) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266) javax.servlet.http.HttpServlet.service(HttpServlet.java:803) com.lab1000.jcom.system.filter.RequestEncodingFilter.doFilter(RequestEncodingFilter.java:30)

root cause

org.hibernate.exception.JDBCConnectionException: could not execute query org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:74) org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43) org.hibernate.loader.Loader.doList(Loader.java:2148) org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2029) org.hibernate.loader.Loader.list(Loader.java:2024) org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:94) org.hibernate.impl.SessionImpl.list(SessionImpl.java:1533) org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:283) com.lab1000.jcom.dao.ArticleDAO.getArticlesUnder(ArticleDAO.java:163) com.lab1000.jcom.struts.action.HomeAction.execute(HomeAction.java:40) org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431) org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236) org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196) org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414) javax.servlet.http.HttpServlet.service(HttpServlet.java:690) javax.servlet.http.HttpServlet.service(HttpServlet.java:803) org.apache.jsp.index_jsp._jspService(index_jsp.java:57) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:803) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266) javax.servlet.http.HttpServlet.service(HttpServlet.java:803) com.lab1000.jcom.system.filter.RequestEncodingFilter.doFilter(RequestEncodingFilter.java:30)

root cause

com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: No operations allowed after connection closed.Connection was implicitly closed due to underlying exception/error:** BEGIN NESTED EXCEPTION ** com.mysql.jdbc.CommunicationsExceptionMESSAGE: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.io.EOFExceptionSTACKTRACE:java.io.EOFException at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1963) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2375) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2874) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1623) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1715) at com.mysql.jdbc.Connection.execSQL(Connection.java:3249) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1268) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1403) at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:139) at org.hibernate.loader.Loader.getResultSet(Loader.java:1669) at org.hibernate.loader.Loader.doQuery(Loader.java:662) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224) at org.hibernate.loader.Loader.doList(Loader.java:2145) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2029) at org.hibernate.loader.Loader.list(Loader.java:2024) at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:94) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1533) at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:283) at com.lab1000.jcom.dao.ArticleDAO.getArticlesUnder(ArticleDAO.java:163) at com.lab1000.jcom.struts.action.HomeAction.execute(HomeAction.java:40) 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.doGet(ActionServlet.java:414) at javax.servlet.http.HttpServlet.service(HttpServlet.java:690) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) 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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:630) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302) at org.apache.jsp.index_jsp._jspService(index_jsp.java:57) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.lab1000.jcom.system.filter.RequestEncodingFilter.doFilter(RequestEncodingFilter.java:30) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) 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:175) 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(Unknown Source)** END NESTED EXCEPTION **Last packet sent to the server was 15 ms ago.STACKTRACE:com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.io.EOFExceptionSTACKTRACE:java.io.EOFException at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1963) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2375) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2874) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1623) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1715) at com.mysql.jdbc.Connection.execSQL(Connection.java:3249) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1268) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1403) at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:139) at org.hibernate.loader.Loader.getResultSet(Loader.java:1669) at org.hibernate.loader.Loader.doQuery(Loader.java:662) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224) at org.hibernate.loader.Loader.doList(Loader.java:2145) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2029) at org.hibernate.loader.Loader.list(Loader.java:2024) at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:94) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1533) at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:283) at com.lab1000.jcom.dao.ArticleDAO.getArticlesUnder(ArticleDAO.java:163) at com.lab1000.jcom.struts.action.HomeAction.execute(HomeAction.java:40) 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.doGet(ActionServlet.java:414) at javax.servlet.http.HttpServlet.service(HttpServlet.java:690) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) 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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:630) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302) at org.apache.jsp.index_jsp._jspService(index_jsp.java:57) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.lab1000.jcom.system.filter.RequestEncodingFilter.doFilter(RequestEncodingFilter.java:30) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) 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:175) 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(Unknown Source)** END NESTED EXCEPTION **Last packet sent to the server was 15 ms ago. at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2586) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2874) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1623) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1715) at com.mysql.jdbc.Connection.execSQL(Connection.java:3249) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1268) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1403) at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:139) at org.hibernate.loader.Loader.getResultSet(Loader.java:1669) at org.hibernate.loader.Loader.doQuery(Loader.java:662) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224) at org.hibernate.loader.Loader.doList(Loader.java:2145) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2029) at org.hibernate.loader.Loader.list(Loader.java:2024) at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:94) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1533) at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:283) at com.lab1000.jcom.dao.ArticleDAO.getArticlesUnder(ArticleDAO.java:163) at com.lab1000.jcom.struts.action.HomeAction.execute(HomeAction.java:40) 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.doGet(ActionServlet.java:414) at javax.servlet.http.HttpServlet.service(HttpServlet.java:690) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) 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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:630) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:436) at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:374) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:302) at org.apache.jsp.index_jsp._jspService(index_jsp.java:57) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at com.lab1000.jcom.system.filter.RequestEncodingFilter.doFilter(RequestEncodingFilter.java:30) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) 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:175) 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(Unknown Source)** END NESTED EXCEPTION ** com.mysql.jdbc.SQLError.createSQLException(SQLError.java:888) com.mysql.jdbc.Connection.checkClosed(Connection.java:1931) com.mysql.jdbc.Connection.prepareStatement(Connection.java:4705) com.mysql.jdbc.Connection.prepareStatement(Connection.java:4671) org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:442) org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:368) org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:105) org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1561) org.hibernate.loader.Loader.doQuery(Loader.java:661) org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:224) org.hibernate.loader.Loader.doList(Loader.java:2145) org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2029) org.hibernate.loader.Loader.list(Loader.java:2024) org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:94) org.hibernate.impl.SessionImpl.list(SessionImpl.java:1533) org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:283) com.lab1000.jcom.dao.ArticleDAO.getArticlesUnder(ArticleDAO.java:163) com.lab1000.jcom.struts.action.HomeAction.execute(HomeAction.java:40) org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431) org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236) org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196) org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414) javax.servlet.http.HttpServlet.service(HttpServlet.java:690) javax.servlet.http.HttpServlet.service(HttpServlet.java:803) org.apache.jsp.index_jsp._jspService(index_jsp.java:57) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:803) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:337) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266) javax.servlet.http.HttpServlet.service(HttpServlet.java:803) com.lab1000.jcom.system.filter.RequestEncodingFilter.doFilter(RequestEncodingFilter.java:30)

　　当时也搞不清楚为什么，但重启Tomcat后就一切回复正常了，但是又过了一天，问题再次出现。仔细分析错误信息，问题肯定出在数据库连接部分，在网上查阅大量信息后，明确了问题的原因：MySQL对所有连接的有效时间默认为28800秒，正好8小时，也就是说，如果一个连接8小时没有请求和操作，就会自动断开；但是对于Hibernate来说，它的连接池并不知道它所管理的连接中是否有被MySQL断开的。如果一个程序要使用数据库连接，而Hibernte的连接池分配一个已经被MySQL断开了的给程序使用，那么便会出现错误。

　　为了证实确实是这个错误，我在本机上做了如下测试：首先启动Tomcat，网站能够正常打开；然后修改系统时间，往后调1天；然后再打开网站，同样的问题果然出现！MySQL + Hibernate架构相当普遍，所以这个问题也相当普遍，若读者也有这样的项目，建议做一下同样的测试，看看是否存在此问题！

　　问题找到了，怎么解决呢？

　　思路1：增大MySQL的连接有效时间；

　　思路2：从程序自身出发，修改连接池的相关参数。

　　显然，思路1是不可行的，一方面这个思路不可能保证这个问题绝对的解决，如果无访问时间够长，还是大于MySQL的连接有效时间，问题同样会发生；另一方面，一般情况下，我们都是将程序部署在别人服务器上，我们不可能去修改MySQL配置。那么只能从思路2入手了。

　　经查资料发现，Hibernate支持如下的连接池：

　　　DriverManagerConnectionProvider：代表由Hibernate提供的默认的数据库连接池

　　　C3P0ConnectionProvider：代表C3P0连接池

　　　ProxoolConnectionProvider：代表Proxool连接池

　　　DBCPConnectionProvider：代表DBCP连接池

　　　DatasourceConnectionProvider：代表在受管理环境中由容器提供的数据源

　　其中，默认连接池并不支持在分配一个连接时，测试其有效与否的功能，而C3P0、Proxool、DBCP都提供了这样的功能，正好可以解决上述问题。综合考虑各个连接池的效率、稳定性、易用性，决定换用Proxool，它确实在各方面表现优良，方便配置。

　　下面就看看如何配置Proxool：

　　1、Hibernate配置文件：

<session-factory>

<property name="hibernate.connection.provider_class">org.hibernate.connection.ProxoolConnectionProvider</property>

<property name="hibernate.proxool.xml">proxool.xml</property>

<property name="hibernate.proxool.pool_alias">mysql</property>

<property name="show_sql">false</property>

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

<mapping resource="com/lab1000/jcom/pojo/Admin.hbm.xml">

...

</session-factory>

　　其中各属性含义如下：

hibernate.connection.provider_class：指明使用Proxool连接池

hibernate.proxool.xml：指明Proxool配置文件所在位置，这里与Hibernate的配置文件在同一目录下

hibernate.proxool.pool_alias：指明要使用的proxool.xml中定义的proxool别名。

　　2、Proxool配置文件（proxool.xml）：

<!---->

<!---->

<something-else-entirely>

<proxool>

<!---->

<alias>mysql</alias>

<!---->

<driver-url>

jdbc:mysql://localhost/yourDatebase?useUnicode=true&characterEncoding=UTF-8

</driver-url>

<!---->

<driver-class>com.mysql.jdbc.Driver</driver-class>

<!---->

<driver-properties>

<property name="user" value="root">

<property name="password" value="password">

</driver-properties>

<!---->

<house-keeping-sleep-time>90000</house-keeping-sleep-time>

<!---->

<maximum-new-connections>20</maximum-new-connections>

<!---->

<prototype-count>3</prototype-count>

<!---->

<maximum-connection-count>20</maximum-connection-count>

<!---->

<minimum-connection-count>3</minimum-connection-count>

<!---->

<test-before-use>true</test-before-use>

<test-after-use>true</test-after-use>

<!---->

<house-keeping-test-sql>SELECT CURRENT_USER</house-keeping-test-sql>

</proxool>

</something-else-entirely>

　　3、下载和安装Proxool的包文件

　　下载地址：http://proxool.sourceforge.net/download.html

　　下载后并解压后，将其中lib文件夹下的jar文件拷贝到你站点的WEB-INF/lib下

　　自此，Proxool配置成功。重新启动Tomcat，再次做上述测试，问题解决。

　　此外，如果要使用C3P0或DHCP，可以参考以下资料：

　　http://blog.csdn.net/lip8654/archive/2008/02/26/2121387.aspx

　　http://azi.iteye.com/blog/182146

　　http://fishyych.iteye.com/blog/90793