tomcat启动filter问题出现error filterStart

Question

我在我的Servlet项目下建了一个HelloFilter.java：package servlet;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class HelloFilter extends HttpServlet implements Filter
{
public void init(FilterConfig config)throws ServletException
{
System.out.println("HelloFilter.init");
}
public void doFilter(ServletRequest requst,ServletResponse response,FilterChain chain)
throws IOException,ServletException
{
System.out.println("HelloFilter.doFilter");
}
public void destroy()
{
System.out.println("HelloFilter.destory");
}
}
类放在servlet文件夹下。我在Servlet项目下的Web.xml配置文件中添加了:
   <filter>
      <filter-name>HelloFilter</filter-name>
      <filter-class>servlet.HelloFilter</filter-class>
   </filter>
  
<filter-mapping>
<filter-name>HelloFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
运行tomcat6.x时就报错：
严重：error filterStart
 org.apache.catalina.startup.HostConfig deployDirectory
严重：Context [/Servlet]startup fail due to previous errors
 org.apache.catalina.startup.HostConfig deployDirectory