报错问题
详细错误见下代码
24-Nov-2020 21:24:22.484 警告 [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [demo] registered the JDBC driver [com.alibaba.druid.proxy.DruidDriver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
24-Nov-2020 21:24:22.484 警告 [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [demo] 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.
24-Nov-2020 21:24:22.485 警告 [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [demo] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144)
com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:80)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
java.lang.Thread.run(Thread.java:748)
24-Nov-2020 21:24:22.485 警告 [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [demo] appears to have started a thread named [Druid-ConnectionPool-Create-730379684] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:1824)
24-Nov-2020 21:24:22.486 警告 [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [demo] appears to have started a thread named [Druid-ConnectionPool-Destroy-730379684] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Thread.sleep(Native Method)
com.alibaba.druid.pool.DruidDataSource$DestroyConnectionThread.run(DruidDataSource.java:1898)
问题描述
web应用程序[demo]注册了JDBC驱动程序[com.mysql.jdbc]。但是当web应用程序停止时无法注销它。为了防止内存泄漏，JDBC驱动程序已被强制取消注册。
web应用程序[演示]似乎已经启动了一个名为[Druid-ConnectionPool-Destroy-730379684]的线程，但未能停止它。这很可能会造成内存泄漏。线程堆栈轨迹:
使用环境
Tomcat Tomcat 8.5.31 + connector-5.1.49 +mysql-5.7 +druid-1.0.9
问题排查
对于一个新手来说，一头雾水，感觉网上瞧一瞧。哇，好多人跟我一样，并且答案就那么几个，全是复制粘贴，每个人的环境也不同，全都试了一遍，也没解决，还是有问题。虽然运行的时候没有问题，但是好恶心人啊。。。必须解决
主要有两个问题，一个是驱动，一个是线程问题。
然后我将网上的代码copy下来，搞监听器，在程序停止时去处理关闭他们； copy下来后，第一个问题出现了，
AbandonedConnectionCleanupThread这个类找不到，看了下导包路径，是在connector连接中，于是马上想到可能 mysql驱动版本问题，然后去中央仓库下载了connector-5.1.49 ，在这个驱动中找到了com.mysql.jdbc.AbandonedConnectionCleanupThread类，但是网上还有com.mysql.cj.jdbc.AbandonedConnectionCleanupThread这个类，都一样的，这个是更高版本的驱动；
然后接着往下走，还报错，AbandonedConnectionCleanupThread.Shutdown(); what ？竟然没有参数，我看别人的都不用传参啊，我的驱动调用这个方法必须传参啊，搞死！！！
然后进去看下方法源码：只有调用了shutDown方法，ok原来如此，然后修改一通，搞定不报错了，配置好监听器，赶紧运行一下试试
我擦，驱动问题没有了，但是连接还有问题，到底是哪的问题咧，然后一直没搞定，请教高人啊！！！
4-Nov-2020 21:57:28.084 警告 [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [demo] appears to have started a thread named [Druid-ConnectionPool-Create-1926858734] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039)
com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:1824)
24-Nov-2020 21:57:28.085 警告 [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [demo] appears to have started a thread named [Druid-ConnectionPool-Destroy-1926858734] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Thread.sleep(Native Method)
com.alibaba.druid.pool.DruidDataSource$DestroyConnectionThread.run(DruidDataSource.java:1898)
24-Nov-2020 21:57:28.097 信息 [main] org.apache.coyote.AbstractProtocol.stop Stopping ProtocolHandler ["http-nio-80"]
24-Nov-2020 21:57:28.100 信息 [main] org.apache.coyote.AbstractProtocol.stop Stopping ProtocolHandler ["ajp-nio-8009"]
24-Nov-2020 21:57:28.103 信息 [main] org.apache.coyote.AbstractProtocol.destroy Destroying ProtocolHandler ["http-nio-80"]
24-Nov-2020 21:57:28.104 信息 [main] org.apache.coyote.AbstractProtocol.destroy Destroying ProtocolHandler ["ajp-nio-8009"]
最后高人给我指点，可能是我连接获取有问题，自己写的JDBCUtil，用的DataSource，让我换DruidDataSource，
dds = (DruidDataSource) DruidDataSourceFactory.createDataSource(pro);
最后，在监听器那里关闭的时候，把这个连接池也关闭掉，修改后，赶紧试一下，卧槽，ok解决了。
贴一下代码，也是在别人的基础上修改来的；
加了这么一句JDBCUtil.getDataSource().close();问题解决了，搞了我一天，哎。。。
public class MyContextListener implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent arg0) {
System.out.println("webService start");
}
@Override
public void contextDestroyed(ServletContextEvent arg0) {
System.out.println("webService stop");
try {
while(DriverManager.getDrivers().hasMoreElements()) {
DriverManager.deregisterDriver(DriverManager.getDrivers().nextElement());
}
System.out.println("jdbc Driver close");
AbandonedConnectionCleanupThread.checkedShutdown();
JDBCUtil.getDataSource().close();
System.out.println("clean thread success");
} catch (SQLException e) {
e.printStackTrace();
}
}
}
在web.xml中配置
<listener>
<listener-class>com.javasm.MyContextListener</listener-class>
</listener>
OK,完美 最后，高人就是高人啊！菜鸡就是菜鸡…
