My class is not a servlet error

I have the following servlet code

public void doPost(HttpServletRequest request, HttpServletResponse response){    Backup bup = new Backup();    bup.doBackup();    response.setContentType("text/html");    PrintWriter out;    try {        out = response.getWriter();    out.println("You backed up your data - well hopefully");    out.flush();    out.close();    } catch (IOException e) {        // TODO Auto-generated catch block        e.printStackTrace();    }}

And the following stack trace

javax.servlet.ServletException: Class view.BackupServlet is not a Servlet org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849) org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454) java.lang.Thread.run(Thread.java:619)

root cause

java.lang.ClassCastException: view.BackupServlet cannot be cast to javax.servlet.Servlet org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849) org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454) java.lang.Thread.run(Thread.java:619)

and the web.xml is

<?xml version="1.0" encoding="UTF-8"?><web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-<br>app_2_4.xsd"><display-name>Backup</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>BackupServlet</description><display-name>BackupServlet</display-name><servlet-name>BackupServlet</servlet-name><br><servlet-class>view.BackupServlet</servlet-class></servlet><servlet-mapping><servlet-name>BackupServlet</servlet-name><url-pattern>/BackupServlet</url-pattern></servlet-mapping></web-app>`