servlet处理表单出现问题

各位:最近才学servlet我写了一个处理表单数据的类FormServlet 能通过编译:放在默认的
%tomcat&\webapps\ROOT\WEB-INF\classes 下 也在web.xml 下注册了
<servlet>
        <servlet-name>FormServlet</servlet-name>
        <servlet-class>FormServlet</servlet-class>
    </servlet>    <servlet-mapping>
        <servlet-name>FormServlet</servlet-name>
        <url-pattern> / servlet/FormServlet</url-pattern>
    </servlet-mapping>可是我通过 http://localhost/servlet/FormServlet 访问出现问题具体情况如下:
到底是怎么回事?能否指点一下!HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception javax.servlet.ServletException: Class FormServlet is not a Servlet
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
java.lang.Thread.run(Thread.java:595)
root cause java.lang.ClassCastException: FormServlet
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
java.lang.Thread.run(Thread.java:595)