遇到"To prevent a memory leak, the JDBC Driver has been forcibly unregistered." 后
2014-3-20 14:20:55 org.apache.catalina.core.StandardContext reload
信息: Reloading this Context has started
2014-03-20 14:20:55,531 [org.springframework.web.context.support.XmlWebApplicationContext]-[INFO] Closing WebApplicationContext for namespace 'mvc-dispatcher-servlet': startup date [Thu Mar 20 11:29:19 CST 2014]; root of context hierarchy
14:20:55.531 [ContainerBackgroundProcessor[StandardEngine[Catalina]]] INFO com.jolbox.bonecp.BoneCP - Shutting down connection pool...
14:20:55.531 [BoneCP-pool-watch-thread] DEBUG com.jolbox.bonecp.PoolWatchThread - Terminating pool watch thread
14:20:55.531 [BoneCP-pool-watch-thread] DEBUG com.jolbox.bonecp.PoolWatchThread - Terminating pool watch thread
14:20:55.531 [BoneCP-pool-watch-thread] DEBUG com.jolbox.bonecp.PoolWatchThread - Terminating pool watch thread
14:20:55.531 [BoneCP-pool-watch-thread] DEBUG com.jolbox.bonecp.PoolWatchThread - Terminating pool watch thread
2014-3-20 14:20:55 org.apache.catalina.core.ApplicationContext log
信息: Destroying Spring FrameworkServlet 'mvc-dispatcher'
14:20:55.546 [ContainerBackgroundProcessor[StandardEngine[Catalina]]] INFO com.jolbox.bonecp.BoneCP - Connection pool has been shutdown.
14:20:55.546 [ContainerBackgroundProcessor[StandardEngine[Catalina]]] DEBUG com.jolbox.bonecp.BoneCPDataSource - Connection pool has been shut down
2014-3-20 14:20:56 org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
严重: The web application [/callcenter] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
2014-3-20 14:20:56 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
严重: The web application [/callcenter] appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak.
2014-3-20 14:20:56 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
严重: The web application [/callcenter] appears to have started a thread named [Timer-0] but has failed to stop it. This is very likely to create a memory leak.最近，在eclipse调试系统时，经常会出现以上异常。
出现条件：web应用，使用spring，连接池用的bonecp。当修改一点代码，save后，spring会重新加载，然后问题就出现了。
在网上查看资料后，找到了该报告：https://issues.apache.org/jira/browse/DBCP-332
原文引用：
BasicDataSource's method close() doesn't deregister JDBC driver. This causes permgen memory leaks in web server environments, during context reloads. For example, using Tomcat 6.0.26 with Spring, and BasicDataSource declared in Spring context, there is a message printed at web application reload:
SEVERE: A web application registered the JBDC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
翻译：
BasicDataSource中的close方法没有注销（deregister）jdbc驱动。在web server环境中，当reload content时，就引起了堆内存泄露（permgen memory leaks）。例如，当在使用spring和tomcat 6.0.26时，BasicDataSource在Spring context被声明了，这样就会有一条信息在web application reload的时候： SEVERE: A web application registered the JBDC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
该地址中 https://issues.apache.org/jira/browse/DBCP-332 提供了一种解决方案。
我并没有使用该方案，因为使用的是bonecp，所以我看了下bonecp的BoneCPDataSource的close方法，发现，其中有个BoneCPConfig类，其中有这个属性：deregisterDriverOnClose。 于是我在spring的xml配置中，加入了该配置。
成功了！！！
再次修改代码，保存时，spring重新加载，成功了，没有异常，但是多打印了一行，大家可以看到：
14:54:52.000 [ContainerBackgroundProcessor[StandardEngine[Catalina]]] INFO com.jolbox.bonecp.BoneCP - Unregistering JDBC driver for : jdbc:mysql://xxx.xxx.xxx.xxx:3306/ccdb?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true全日志如下：
14:54:51.984 [ContainerBackgroundProcessor[StandardEngine[Catalina]]] INFO com.jolbox.bonecp.BoneCP - Shutting down connection pool...
14:54:52.000 [BoneCP-pool-watch-thread] DEBUG com.jolbox.bonecp.PoolWatchThread - Terminating pool watch thread
14:54:52.000 [BoneCP-pool-watch-thread] DEBUG com.jolbox.bonecp.PoolWatchThread - Terminating pool watch thread
14:54:52.000 [BoneCP-pool-watch-thread] DEBUG com.jolbox.bonecp.PoolWatchThread - Terminating pool watch thread
14:54:52.000 [BoneCP-pool-watch-thread] DEBUG com.jolbox.bonecp.PoolWatchThread - Terminating pool watch thread
14:54:52.000 [ContainerBackgroundProcessor[StandardEngine[Catalina]]] INFO com.jolbox.bonecp.BoneCP - Unregistering JDBC driver for : jdbc:mysql://xxx.xxx.xxx.xxx:3306/ccdb?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true
14:54:52.000 [ContainerBackgroundProcessor[StandardEngine[Catalina]]] INFO com.jolbox.bonecp.BoneCP - Connection pool has been shutdown.2014-3-20 14:54:52 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
严重: The web application [/callcenter] appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak.
2014-3-20 14:54:52 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
严重: The web application [/callcenter] appears to have started a thread named [Timer-0] but has failed to stop it. This is very likely to create a memory leak.