Problem in running the servlet

Question

I have compiled the servlet and put the class file HelloWorld.class inside
$CATALINA_HOME$/webapps/ROOT/WEB-INF/classes/
directory, under tomcat6.0.18
and also mapped servlet in
$CATALINA_HOME$/webapps/ROOT/WEB-INF/web.xml, as below
web.xml:
    <?xml version="1.0" encoding="ISO-8859-1"?>
<!--
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  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at
      http://www.apache.org/licenses/LICENSE-2.0
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  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
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<web-app xmlns="http://java.sun.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
   version="2.5">
  <display-name>Welcome to Tomcat</display-name>
  <description>
     Welcome to Tomcat
  </description>
  <servlet>
    <servlet-name>HelloWorld</servlet-name>
    <servlet-class>HelloWorld</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>HelloWorld</servlet-name>
    <url-pattern>/HelloWorld</url-pattern>
  </servlet-mapping>
</web-app>and run the servlet using this url......*.http://localhost/HelloWorld*
but I got following error code under tomcat 6.0.18
  type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
javax.servlet.ServletException: Error allocating a servlet instance
     org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
     org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
     org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
     org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
     org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
     java.lang.Thread.run(Thread.java:619)
root cause
java.lang.NoClassDefFoundError: HelloWorld (wrong name: hall/HelloWorld)
     java.lang.ClassLoader.defineClass1(Native Method)
     java.lang.ClassLoader.defineClass(ClassLoader.java:620)
     java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
     org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1847)
     org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:890)
     org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1354)
     org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233)
     org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
     org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
     org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
     org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
     org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
     java.lang.Thread.run(Thread.java:619)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.18 logs.is there something I did wrong?
Edited by: san_4u on Mar 16, 2009 1:20 AM

Answer 1

root cause
java.lang.NoClassDefFoundError: HelloWorld (wrong name: hall/HelloWorld)Is your servlet contains first line as package hall;If it is there,remove it from the servlet code. And run your program.
If you want to keep it, then make a folder named hall in classes folder and put your HelloWorld.class there. Also change <servlet-class> as
<servlet>
    <servlet-name>HelloWorld</servlet-name>
    <servlet-class>hall.HelloWorld</servlet-class>
  </servlet>