title: Mysql AbandonedConnectionCleanupThread Error
body: <p>I want deploy a spring boot web application on tomcat external but error, I can't fix it. Please help me, thank you very much.</p>
  
  <p><strong>application.properties</strong></p>
  
  <pre><code>server.port=8080
  spring.datasource.url=jdbc:mysql://localhost:3306/springboot?useUnicode=yes&amp;characterEncoding=UTF-8&amp;useSSL=false&amp;allowPublicKeyRetrieval=true
  spring.datasource.username=root
  spring.datasource.password=root
  spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
  
  spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQLDialect
  #spring.jpa.properties.hibernate.id.new_generator_mappings = false
  spring.jpa.properties.hibernate.format_sql = true
  </code></pre>
  
  <p><strong>Log</strong></p>
  
  <pre><code>java.lang.Object.wait(Native Method)
   java.lang.ref.ReferenceQueue.remove(Unknown Source)
   com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:70)
   java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
   java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
   java.lang.Thread.run(Unknown Source)
  14-Jan-2019 16:25:53.860 INFO [http-nio-8080-exec-2] org.apache.catalina.startup.HostConfig.deployWAR Deployment of web application archive C:\Server\Tomcat-8.5\webapps\springboot-0.0.1-SNAPSHOT.war has finished in 12,765 ms
  14-Jan-2019 16:25:54.713 INFO [Abandoned connection cleanup thread] org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading Illegal access: this web application instance has been stopped already. Could not load []. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
   java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load []. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
          at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1305)
          at org.apache.catalina.loader.WebappClassLoaderBase.getResource(WebappClassLoaderBase.java:986)
          at com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.checkContextClassLoaders(AbandonedConnectionCleanupThread.java:96)
          at com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:69)
          at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
          at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
          at java.lang.Thread.run(Unknown Source)
  </code></pre>