C3P0 pools 使用中的一个问题解决

新开发的一个网站，每天早上来开就有访问数据库的操作就出现异常，数据库为Mysql。也就是说在运行中每个一段长的空闲时间就出现异常，异常为:

异常代码

** BEGIN NESTED EXCEPTION **

com.mysql.jdbc.CommunicationsException
MESSAGE: Communications link failure due to underlying exception:

** BEGIN NESTED EXCEPTION **

java.net.SocketException
MESSAGE: Software caused connection abort: socket write error

STACKTRACE:

java.net.SocketException: Software caused connection abort: socket write error
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:92)
at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:65)
at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:123)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:2590)
at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:2523)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1517)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1626)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3031)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:943)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1049)
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.hql.QueryLoader.list(QueryLoader.java:375)
at org.hibernate.hql.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:308)
at org.hibernate.engine.query.HQLQueryPlan.performList(HQLQueryPlan.java:153)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1106)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:79)
at org.hibernate.hopeDAO.StudentDBentity.findStudent(StudentDBentity.java:75)
at com.hope.student.action.StudentAction.execute(StudentAction.java:483)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
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.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
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:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:595)


** 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:

查看了Mysql的文档，以及Connector/J的文档以及在线说明发现，出现这种异常的原因是：Mysql服务器默认的“wait_timeout”是8小时，也就是说一个connection空闲超过8个小时，Mysql将自动断开该 connection。这就是问题的所在，在C3P0 pools中的connections如果空闲超过8小时，Mysql将其断开，而C3P0并不知道该connection已经失效，如果这时有 Client请求connection，C3P0将该失效的Connection提供给Client，将会造成上面的异常。

解决的方法有3种：

1.增加wait_timeout的时间。

2.减少Connection pools中connection的lifetime。

3.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，下面就对hibernate使用C3P0分别做一说明，假设wait_timeout为默认的8小时。

?

Hibernate使用C3P0的连接池，并队c3p0配置。

1.导入c3p0.jar包，hibernate自带的包，也可以在网上下载一个。

2.Hibernate的配置文件，hibernate.cfg.xml中增加：

<property name="c3p0.acquire_increment">1</property>

????????????? <property name="c3p0.idle_test_period">100</property>

????????????? <property name="c3p0.max_size">5</property>

<property name="c3p0.max_statements">0</property>

????????????? <property name="c3p0.min_size">2</property>

?????? ?????? <property name="c3p0.timeout">90</property>

????????????? <property name="c3p0.preferredTestQuery ">select 1 from user where id=1</property>

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

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

<property name="c3p0.testConnectionOnCheckout">true</property>

3.重新启动tomcat，问题解决。

评论

2 楼 tianmingqi 2009-01-10  

干脆放在我邮箱里吧，
[e-mail]
我真的很急用，先谢谢大侠了，麻烦你！

1 楼 tianmingqi 2009-01-10  

老大你再写一下吧，你的第二步2.Hibernate的配置文件，hibernate.cfg.xml中增加的内容为乱码，我现在也遇到了这个问题，急等用啊，在线=