//Tomcat Localhost Log信息

org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [Servlet] in context with path [] threw exception [Servlet execution threw an exception] with root cause

 java.lang.ClassNotFoundException: org.apache.commons.io.IOUtils

    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1269)

    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1104)

    at servlet.Servlet.doGet(Servlet.java:29)

    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)

    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:475)

    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)

    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80)

    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)

    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)

    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)

    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:498)

    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)

    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:796)

    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1374)

    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)

    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)

    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)

    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)

    at java.lang.Thread.run(Thread.java:745)

 @WebServlet(name = "Servlet",urlPatterns = "/Servlet")

 public class Servlet extends HttpServlet {

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         Class c = this.getClass();

         InputStream input = c.getResourceAsStream("a.txt");

         String str = IOUtils.toString(input,"utf-8");//问题所在之处

         System.out.println(str);

     }

 }