java源程序如下
import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.*;

/**
 * 计算并记录请求的响应时间到日志文件
 */
public class ResponseTimeFilter implements Filter {

    protected FilterConfig config;

    public void init(FilterConfig filterConfig) throws ServletException {
        this.config = filterConfig;
    }

    // 需要重点实现的方法
    public void doFilter(
        ServletRequest request,
        ServletResponse response,
        FilterChain chain)
        throws IOException, ServletException {

        // 响应开始时间
        long startTime = System.currentTimeMillis();

        // 将请求转发给过滤器链上其他对象
        chain.doFilter(request, response);

        // 计算请求的响应时间
        long elapsed = System.currentTimeMillis() - startTime;

        String name = "default";
        if (request instanceof HttpServletRequest) {
            name = ((HttpServletRequest) request).getRequestURI();
        }

        // 将请求的响应时间记录到日志文件
        config.getServletContext().log(name + " took " + elapsed + " ms");

    }

    public void destroy() {

    }

}


wed.xml配置信息如下
<filter>
    <filter-name>RseponseTimeFilter</filter-name>
    <filter-class>ch16.RseponseTimeFilter</filter-class>
    </filter>
    <filter-mapping>
    <filter-name>RseponseTimeFilter</filter-name>
    <url-pattern>/*</url-pattern>
    </filter-mapping>
    
    
    
    
    启动tomcat是出现如下错误信息
    严重: Error filterStart
2007-11-16 10:01:34 org.apache.catalina.core.StandardContext start
严重: Context [/serlet] startup failed due to previous errors

请高手看看.原因是什么.谢谢