Premesso che ho installato Tomcat e javasdk e funziona tutto! Ho provato a creare una cartella in Webapp e a creare dentro WEB-INF e poi CLASSES.
Ho infilato in Classes HelloWorldServlet.class e creato il web.xml che ho messo in WEB-INF.
Poi con un file html richiamo la classe ma dice errore 500!
Come mai?
Soul
Web.xml----------------------------------------------
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<display-name>
hello
</display-name>
<description>
none
</description>
<servlet>
<servlet-name>
hello
</servlet-name>
<description>
descrizione
</description>
<servlet-class>
HelloWorldServlet.class
</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>
hello
</servlet-name>
<url-pattern>
/adegamisu
</url-pattern>
</servlet-mapping>
</web-app>
file html----------------------------------------------
<HTML>
<HEAD>
<TITLE>esecuzione servlet</TITLE>
</HEAD>
<BODY>
<form method="GET" action="adegamisu">
<input type="submit" value="Invia">
</p>
</form>
</BODY>
</HTML>
Errore--------------------------------------------------
The server encountered an internal error () that prevented it from fulfilling this request.
exception
javax.servlet.ServletException: Wrapper cannot find servlet class HelloWorldServlet.class or a class it depends on
org.apache.catalina.valves.ErrorReportValve.invoke (ErrorReportValve.java:117)
org.apache.coyote.tomcat5.CoyoteAdapter.service(Co yoteAdapter.java:160)
org.apache.coyote.http11.Http11Processor.process(H ttp11Processor.java:793)
org.apache.coyote.http11.Http11Protocol$Http11Conn ectionHandler.processConnection(Http11Protocol.jav a:702)
org.apache.tomcat.util.net.TcpWorkerThread.runIt(P oolTcpEndpoint.java:571)
org.apache.tomcat.util.threads.ThreadPool$ControlR unnable.run(ThreadPool.java:644)
java.lang.Thread.run(Unknown Source)
root cause
java.lang.ClassNotFoundException: HelloWorldServlet.class
org.apache.catalina.loader.WebappClassLoader.loadC lass(WebappClassLoader.java:1340)
org.apache.catalina.loader.WebappClassLoader.loadC lass(WebappClassLoader.java:1189)
org.apache.catalina.valves.ErrorReportValve.invoke (ErrorReportValve.java:117)
org.apache.coyote.tomcat5.CoyoteAdapter.service(Co yoteAdapter.java:160)
org.apache.coyote.http11.Http11Processor.process(H ttp11Processor.java:793)
org.apache.coyote.http11.Http11Protocol$Http11Conn ectionHandler.processConnection(Http11Protocol.jav a:702)
org.apache.tomcat.util.net.TcpWorkerThread.runIt(P oolTcpEndpoint.java:571)
org.apache.tomcat.util.threads.ThreadPool$ControlR unnable.run(ThreadPool.java:644)
java.lang.Thread.run(Unknown Source)
GRAZIE A TUTTI!
" ho copiato tutti i jar in quelle cartelle ed ora non riparte TOMCAT! o meglio parte ma non visualizza il sito 
