严重: The web application [/service] 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.  
一月 25, 2018 11:58:37 上午 org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc  
严重: The web application [/service] 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.  
一月 25, 2018 11:58:37 上午 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads  
严重: The web application [/service] 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.  
一月 25, 2018 11:58:37 上午 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads  
严重: The web application [/service] appears to have started a thread named [New I/O worker #1] but has failed to stop it. This is very likely to create a memory leak.  
一月 25, 2018 11:58:37 上午 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads  
严重: The web application [/service] appears to have started a thread named [New I/O worker #2] but has failed to stop it. This is very likely to create a memory leak.  
一月 25, 2018 11:58:37 上午 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads  
严重: The web application [/service] appears to have started a thread named [New I/O worker #3] but has failed to stop it. This is very likely to create a memory leak.  
一月 25, 2018 11:58:37 上午 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads  
严重: The web application [/service] appears to have started a thread named [New I/O worker #4] but has failed to stop it. This is very likely to create a memory leak.

2. 错误原因
  从字面翻译：为了防止内存泄漏，JDBC驱动程序已经被强制注销。

3. 解决办法
  将Tomcat中server.xml监听器注释掉，重启tomcat
  vi tomcat9/conf/server.xml //注释如下两行：
  
<?xml version='1.0' encoding='utf-8'?>
<Server port="8709" shutdown="SHUTDOWN">
  <!--
  <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" />
  <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" />
  -->

参考： http://ian.wang/309.htm