修改class或xml文件，重启异常tomcat异常_[abandoned connection cleanup thread] org.apache.c

[Abandoned connection cleanup thread] org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading Illegal access: this web application instance has been stopped already. Could not load []. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
 java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load []. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
	at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1305)
	at org.apache.catalina.loader.WebappClassLoaderBase.getResource(WebappClassLoaderBase.java:986)
	at com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.checkContextClassLoaders(AbandonedConnectionCleanupThread.java:96)
	at com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:69)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)

修改部分class或者配置文件后重启tomcat出现以上异常。发现的问题是在修改mapper目录下的xml文件后，将原文件备份成xxx_bak.xml。导致项目无法启动。正确的修改方法是将修改的文件名改为xxx.xml.bak