Tomcat: Class not found exception - eclipse

Question

I'm developing a servlet running on Tomcat 6 using Eclipse as IDE.
The main path of the web application is "Calcolatrice" and the name of the servlet id "Calcolatrice" too.
When I try to execute a simple get operation on the servlet the following exception is throwed:
javax.servlet.ServletException: Wrapper cannot find servlet class as.unibo.Calcolatrice or a class it depends on
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
java.lang.Thread.run(Thread.java:680)
root cause
java.lang.ClassNotFoundException: as.unibo.Calcolatrice
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1680)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1526)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
java.lang.Thread.run(Thread.java:680)
What I cannot understand is why the package where is the servlet is "as.unibo.polac.server" but Tomcat searches it in another package "as.unibo".
Which could be the reason of this problem?
[EDIT]
This is the content of my web.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>Calcolatrice</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<description></description>
<display-name>Calcolatrice</display-name>
<servlet-name>Calcolatrice</servlet-name>
<servlet-class>as.unibo.Calcolatrice</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Calcolatrice</servlet-name>
<url-pattern>/Calcolatrice</url-pattern>
</servlet-mapping>
</web-app>
Is it correct?

Answer 1

Because your servlet is in as.unibo.polac.server package your web.xml should be:
....
<servlet>
<description></description>
<display-name>Calcolatrice</display-name>
<servlet-name>Calcolatrice</servlet-name>
<servlet-class>as.unibo.polac.server.Calcolatrice</servlet-class>
</servlet>
.....
The class path is wrong in your web.xml. Update it.