title: How to resolve WebappClassLoaderBase
body: <p><strong>When I am starting the server, it is getting started but I am getting errors. Due to this not able to do APIs call. These are the errors.</strong></p>
  
  <pre><code>Jul 18, 2018 11:05:36 PM com.mongodb.ServerMonitor$ServerMonitorRunnable run
  WARNING: Exception in monitor thread during notification of server state change
  java.lang.NoClassDefFoundError: com/mongodb/ChangeEvent
      at com.mongodb.ServerMonitor$ServerMonitorRunnable.sendStateChangedEvent(ServerMonitor.java:136)
      at com.mongodb.ServerMonitor$ServerMonitorRunnable.run(ServerMonitor.java:119)
      at java.lang.Thread.run(Unknown Source)
  Caused by: java.lang.ClassNotFoundException: Illegal access: this web application instance has been stopped already. Could not load [com.mongodb.ChangeEvent]. 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.checkStateForClassLoading(WebappClassLoaderBase.java:1362)
      at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1219)
      at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1180)
      ... 3 more
  Caused by: java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [com.mongodb.ChangeEvent]. 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:1372)
      at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1360)
      ... 5 more
  
  Jul 18, 2018 11:05:36 PM org.apache.catalina.loader.WebappClassLoaderBase checkStateForResourceLoading
  INFO: Illegal access: this web application instance has been stopped already. Could not load [java.util.concurrent.locks.Condition]. 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 [java.util.concurrent.locks.Condition]. 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:1372)
      at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1360)
      at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1219)
      at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1180)
      at com.mongodb.ServerMonitor$ServerMonitorRunnable.waitForSignalOrTimeout(ServerMonitor.java:177)
      at com.mongodb.ServerMonitor$ServerMonitorRunnable.waitForNext(ServerMonitor.java:158)
      at com.mongodb.ServerMonitor$ServerMonitorRunnable.run(ServerMonitor.java:124)
      at java.lang.Thread.run(Unknown Source)
  
  Exception in thread "cluster-2-34.214.191.171:27017" java.lang.NoClassDefFoundError: java/util/concurrent/locks/Condition
      at com.mongodb.ServerMonitor$ServerMonitorRunnable.waitForSignalOrTimeout(ServerMonitor.java:177)
      at com.mongodb.ServerMonitor$ServerMonitorRunnable.waitForNext(ServerMonitor.java:158)
      at com.mongodb.ServerMonitor$ServerMonitorRunnable.run(ServerMonitor.java:124)
      at java.lang.Thread.run(Unknown Source)
  </code></pre>