解决mysql自动断掉连接的问题
这两周做了个手机的后台程序，数据库为MySQL5.0，持久层使用Hibernate 3.0，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。部署到服务器上，没发现什么问题。等到第二天，同事调用接口时，提示错误，但是重启tomcat后问题就解决了。前两天没有时间，今天又出现问题了，问题如下图所示.
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.hibernate.exception.JDBCConnectionException: could not execute query org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:97) org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) org.hibernate.loader.Loader.doList(Loader.java:2235) org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129) org.hibernate.loader.Loader.list(Loader.java:2124) org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401) org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363) org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149) org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) com.swift.softwarestore.service.IConDownloadAction.doPost(IConDownloadAction.java:100) com.swift.softwarestore.service.IConDownloadAction.doGet(IConDownloadAction.java:76) javax.servlet.http.HttpServlet.service(HttpServlet.java:621) javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
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.CommunicationsException MESSAGE: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.SocketException MESSAGE: 断开的管道 STACKTRACE: java.net.SocketException: 断开的管道 at java.net.SocketOutputStream.socketWrite0(Native Method) at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:109) at java.net.SocketOutputStream.write(SocketOutputStream.java:153) at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82) at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140) at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:2744) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1612) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1723) at com.mysql.jdbc.Connection.execSQL(Connection.java:3283) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1332) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1467) at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208) at org.hibernate.loader.Loader.getResultSet(Loader.java:1812) at org.hibernate.loader.Loader.doQuery(Loader.java:697) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259) at org.hibernate.loader.Loader.doList(Loader.java:2232) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129) at org.hibernate.loader.Loader.list(Loader.java:2124) at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401) at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363) at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149) at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) at com.swift.softwarestore.service.SoftwareInfoAction.doprint(SoftwareInfoAction.java:146) at com.swift.softwarestore.service.SoftwareInfoAction.doPost(SoftwareInfoAction.java:86) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) 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 org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169) 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:98) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) 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:999) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:722) ** END NESTED EXCEPTION ** Last packet sent to the server was 1 ms ago. STACKTRACE: com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying exception: ** BEGIN NESTED EXCEPTION ** java.net.SocketException MESSAGE: 断开的管道 STACKTRACE: java.net.SocketException: 断开的管道 at java.net.SocketOutputStream.socketWrite0(Native Method) at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:109) at java.net.SocketOutputStream.write(SocketOutputStream.java:153) at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82) at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140) at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:2744) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1612) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1723) at com.mysql.jdbc.Connection.execSQL(Connection.java:3283) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1332) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1467) at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208) at org.hibernate.loader.Loader.getResultSet(Loader.java:1812) at org.hibernate.loader.Loader.doQuery(Loader.java:697) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259) at org.hibernate.loader.Loader.doList(Loader.java:2232) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129) at org.hibernate.loader.Loader.list(Loader.java:2124) at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401) at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363) at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149) at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) at com.swift.softwarestore.service.SoftwareInfoAction.doprint(SoftwareInfoAction.java:146) at com.swift.softwarestore.service.SoftwareInfoAction.doPost(SoftwareInfoAction.java:86) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) 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 org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169) 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:98) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) 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:999) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:722) ** END NESTED EXCEPTION ** Last packet sent to the server was 1 ms ago. at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:2759) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1612) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1723) at com.mysql.jdbc.Connection.execSQL(Connection.java:3283) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1332) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1467) at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208) at org.hibernate.loader.Loader.getResultSet(Loader.java:1812) at org.hibernate.loader.Loader.doQuery(Loader.java:697) at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259) at org.hibernate.loader.Loader.doList(Loader.java:2232) at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129) at org.hibernate.loader.Loader.list(Loader.java:2124) at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401) at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363) at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149) at org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) at com.swift.softwarestore.service.SoftwareInfoAction.doprint(SoftwareInfoAction.java:146) at com.swift.softwarestore.service.SoftwareInfoAction.doPost(SoftwareInfoAction.java:86) at javax.servlet.http.HttpServlet.service(HttpServlet.java:641) 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 org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169) 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:98) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) 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:999) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:722) ** END NESTED EXCEPTION ** com.mysql.jdbc.SQLError.createSQLException(SQLError.java:888) com.mysql.jdbc.Connection.checkClosed(Connection.java:1932) com.mysql.jdbc.Connection.prepareStatement(Connection.java:4768) com.mysql.jdbc.Connection.prepareStatement(Connection.java:4734) org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:534) org.hibernate.jdbc.AbstractBatcher.getPreparedStatement(AbstractBatcher.java:452) org.hibernate.jdbc.AbstractBatcher.prepareQueryStatement(AbstractBatcher.java:161) org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1577) org.hibernate.loader.Loader.doQuery(Loader.java:696) org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:259) org.hibernate.loader.Loader.doList(Loader.java:2232) org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2129) org.hibernate.loader.Loader.list(Loader.java:2124) org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:401) org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:363) org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:196) org.hibernate.impl.SessionImpl.list(SessionImpl.java:1149) org.hibernate.impl.QueryImpl.list(QueryImpl.java:102) com.swift.softwarestore.service.IConDownloadAction.doPost(IConDownloadAction.java:100) com.swift.softwarestore.service.IConDownloadAction.doGet(IConDownloadAction.java:76) javax.servlet.http.HttpServlet.service(HttpServlet.java:621) javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.27 logs.
在网上查了查，说是需要修改mysql的配置文件my.cnf.原因是mysql默认8个小时内无请求就断掉连接。需要在mysqld后添加wait_timeout=172800，interactive_timeout=172800这两行配置参数，但是后来发现这样也不能除根啊。
在网上找的解决方案：
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）：
<?xml version="1.0" encoding="UTF-8"?>
<!-- the proxool configuration can be embedded within your own application's.
Anything outside the "proxool" tag is ignored. -->
<something-else-entirely>
<proxool>
<!-- proxool别名 -->
<alias>mysql</alias>
<!-- 数据库连接Url -->
<driver-url>
jdbc:mysql://localhost/yourDatebase?useUnicode=true&characterEncoding=UTF-8
</driver-url>
<!-- JDBC驱动名称 -->
<driver-class>com.mysql.jdbc.Driver</driver-class>
<!-- 数据库连接帐号 -->
<driver-properties>
<property name="user" value="root" />
<property name="password" value="password" />
</driver-properties>
<!-- proxool自动侦察各个连接状态的时间间隔(毫秒),侦察到空闲的连接就马上回收,超时的销毁 -->
<house-keeping-sleep-time>90000</house-keeping-sleep-time>
<!-- 指因未有空闲连接可以分配而在队列中等候的最大请求数,超过这个请求数的用户连接就不会被接受 -->
<maximum-new-connections>20</maximum-new-connections>
<!-- 最少保持的空闲连接数 -->
<prototype-count>3</prototype-count>
<!-- 允许最大连接数,超过了这个连接，再有请求时，就排在队列中等候，最大的等待请求数由maximum-new-connections决定 -->
<maximum-connection-count>20</maximum-connection-count>
<!-- 最小连接数 -->
<minimum-connection-count>3</minimum-connection-count>
<!-- 在分配连接前后是否进行有效性测试，这个是解决本问题的关键 -->
<test-before-use>true</test-before-use>
<test-after-use>true</test-after-use>
<!-- 用于测试的SQL语句 -->
<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.javaeye.com/blog/182146
http://fishyych.javaeye.com/blog/90793
修改如下JDBC连接的 URL：
jdbc:mysql://hostaddress:3306/schemaname?autoReconnect=true
//jdbc:mysql://192.168.1.110:3306/st_softwarestore_db?autoReconnect=true
添加 autoReconnect=true 这个参数，即能解决这个问题。