java.lang.ClassNotFoundException: com.mysql.cj.jdbc.AbandonedConnectionCleanupThread

在停止tomcat的时候在localhost.2019-08-28.log 报错：

27-Aug-2019 21:23:50.410 SEVERE [localhost-startStop-2] org.apache.catalina.core.StandardContext.listenerStop Exception sending context destroyed event to listener instance of class com.test.receive.servlet.DataBaseListener
 java.lang.NoClassDefFoundError: com/mysql/cj/jdbc/AbandonedConnectionCleanupThread
        at com.asiainfo.receive.servlet.DataBaseListener.contextDestroyed(DataBaseListener.java:27)
        at org.apache.catalina.core.StandardContext.listenerStop(StandardContext.java:4947)
        at org.apache.catalina.core.StandardContext.stopInternal(StandardContext.java:5586)
        at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:221)
        at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1426)
        at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1415)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.ClassNotFoundException: com.mysql.cj.jdbc.AbandonedConnectionCleanupThread
        at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1352)
        at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1180)
        ... 10 more

在catalina.out的错误虽然是警告，但是看着很不对劲

28-Aug-2019 18:29:57.472 INFO [main] org.apache.catalina.core.StandardServer.await A valid shutdown command was received via the shutdown port. Stopping the Server instance.
28-Aug-2019 18:29:57.473 INFO [main] org.apache.coyote.AbstractProtocol.pause Pausing ProtocolHandler ["http-nio-1301"]
28-Aug-2019 18:29:57.524 INFO [main] org.apache.coyote.AbstractProtocol.pause Pausing ProtocolHandler ["ajp-nio-8019"]
28-Aug-2019 17:59:14.607 INFO [main] org.apache.catalina.core.StandardService.stopInternal Stopping service Catalina
28-Aug-2019 17:59:14.615 WARNING [localhost-startStop-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [ROOT] 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. Stack trace of thread:
 java.lang.Object.wait(Native Method)
 java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
 com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:41)
28-Aug-2019 17:59:14.625 WARNING [localhost-startStop-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [api] 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.
28-Aug-2019 17:59:14.625 WARNING [localhost-startStop-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [api] appears to have started a thread named [Timer-0] 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.util.TimerThread.mainLoop(Timer.java:552)
 java.util.TimerThread.run(Timer.java:505)
28-Aug-2019 17:59:14.626 WARNING [localhost-startStop-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [api] 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. Stack trace of thread:
 java.lang.Object.wait(Native Method)
 java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
 com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:41)

在localhost.2019-08-28.log重要的是这句：

Caused by: java.lang.ClassNotFoundException: com.mysql.cj.jdbc.AbandonedConnectionCleanupThread

这两个日志报的错应该是用一个意思

看到有同学和我一样的错误，根据此同学 链接 的解决办法：

package com.test.receive.servlet;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Date;
import java.util.Enumeration;
import java.util.Timer;

import com.test.receive.utils.pswd.DbIntervalUtil;
import com.mysql.jdbc.AbandonedConnectionCleanupThread;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class DataBaseListener implements ServletContextListener {
private Timer timer = null;
	@Override
	public void contextDestroyed(ServletContextEvent sce) {
	    Enumeration<Driver> drivers = DriverManager.getDrivers();
	    Driver d = null;
	    while (drivers.hasMoreElements()) {
	        try {
	            d = drivers.nextElement();
	            DriverManager.deregisterDriver(d);
	            System.out.println(String.format("ContextFinalizer:Driver %s deregistered", d));
	        } catch (SQLException ex) {
	            System.out.println(String.format("ContextFinalizer:Error deregistering driver %s", d) + ":" + ex);
	        }
	    }
	    try {
	        AbandonedConnectionCleanupThread.shutdown();
	    } catch (InterruptedException e) {
	        System.out.println("ContextFinalizer:SEVERE problem cleaning up: " + e.getMessage());
	        e.printStackTrace();
	    }
	}
}

修改后localhost.2019-08-28.log 不报错了，所以localhost.2019-08-28.log 报错的原因是
我本该引用
import com.mysql.jdbc.AbandonedConnectionCleanupThread;
但是却引用了
import com.mysql.cj.jdbc.AbandonedConnectionCleanupThread;

而catalina.out的警告依旧在，再找找解决办法吧。