错误描述：单独有运行durid连接池操作数据库，以及单独获取servlet的doPost都正确，但是在doPost中运行写了通过durid操作数据库的方法报错：ClassNotFoundException: com.alibaba.druid.pool.DruidDataSourceFactory

错误代码：

2月 23, 2020 4:26:45 下午 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet [login.Login] in context with path [/MiWeb] threw exception [Servlet execution threw an exception] with root cause
java.lang.ClassNotFoundException: com.alibaba.druid.pool.DruidDataSourceFactory
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1343)
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1173)
	at login.JDBCUtils.<clinit>(JDBCUtils.java:24)
	at login.UserDo.getUser(UserDo.java:24)
	at login.Login.doPost(Login.java:31)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:668)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:834)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1417)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Thread.java:834)

2月 23, 2020 4:31:14 下午 org.apache.catalina.core.StandardContext reload
信息: Reloading Context with name [/MiWeb] has started
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.catalina.loader.WebappClassLoaderBase (file:/F:/tomcat/apache-tomcat-9.0.14/lib/catalina.jar) to field java.io.ObjectStreamClass$Caches.localDescs
WARNING: Please consider reporting this to the maintainers of org.apache.catalina.loader.WebappClassLoaderBase
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
2月 23, 2020 4:31:14 下午 org.apache.catalina.core.StandardContext reload
信息: Reloading Context with name [/MiWeb] is completed
2月 23, 2020 4:32:35 下午 org.apache.catalina.core.StandardContext reload
信息: Reloading Context with name [/MiWeb] has started
2月 23, 2020 4:32:35 下午 org.apache.catalina.core.StandardContext reload
信息: Reloading Context with name [/MiWeb] is completed

　解决方案　

1. 折腾了两天，才发现，应该是jar包没有导对，jar包应该先放到WEB_INF目录下的lib中，在BuidPath一下，但是我是直接放在了项目的根目录下，直接BuildPath