javax.servlet.ServeretException:Error instantiating servlet class[com.xxx.xxxservlet]の解決策

      servlet    servlet，    ，  Tomcat          ：
javax.servlet.ServletException: Error instantiating servlet class [com.java.servlet.demo1servlet]
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:412)
org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1385)
org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Unknown Source)

第一反応はwebです.xmlはservlet名を変更せずにwebを開く.xmlはやはり変更されていないので、両側servlet-nameが一致せず、過去をマッピングできず、手動で修正して正常です.