public class FilterManager {

  public void processFilter(Filter target,

    javax.servlet.http.HttpServletRequest request,

    javax.servlet.http.HttpServletResponse response)

    throws javax.servlet.ServletException,

      java.io.IOException       {

    FilterChain filterChain = new FilterChain();

     //过滤器管理器在此构建过滤器链

    //如有必要

    //通过过滤器链管理请求

    filterChain.processFilter(request, response);

      //进程目标资源

    target.execute(request, response);

  }

}

public class FilterChain {

  //过滤器链 filter chain

  private Vector myFilters = new Vector();

  // 创建新的 FilterChain

  public FilterChain()  {

    // 插件默认过滤服务为例

    // 只要。这通常会在

    // FilterManager，但是在这里完成了例子目的

    addFilter(new DebugFilter());

    addFilter(new LoginFilter());

    addFilter(new AuditFilter());

  }

  public void processFilter(

    javax.servlet.http.HttpServletRequest request,

    javax.servlet.http.HttpServletResponse response)

  throws javax.servlet.ServletException,

    java.io.IOException         {

    Filter filter;

    // 应用过滤器

    Iterator filters = myFilters.iterator();//迭代器过滤器

    while (filters.hasNext())

    {

      filter = (Filter)filters.next();

      //通过各种请求和响应

      //筛选器

      filter.execute(request, response);

    }

  }

  public void addFilter(Filter filter)  {

    myFilters.add(filter);

  }

}

public class BaseEncodeFilter implements

      javax.servlet.Filter {

  private javax.servlet.FilterConfig myFilterConfig;

  public BaseEncodeFilter()     {  }

  public void doFilter(

    javax.servlet.ServletRequest servletRequest,

    javax.servlet.ServletResponse servletResponse,

    javax.servlet.FilterChain filterChain)

  throws java.io.IOException,

    javax.servlet.ServletException {

    filterChain.doFilter(servletRequest,

        servletResponse);

  }

  public javax.servlet.FilterConfig getFilterConfig()

  {

    return myFilterConfig;

  }

  public void setFilterConfig(

    javax.servlet.FilterConfig filterConfig) {

      myFilterConfig = filterConfig;

  }

}

public class StandardEncodeFilter

  extends BaseEncodeFilter {

  //创建新的 StandardEncodeFilter

  public StandardEncodeFilter()   {  }

  public void doFilter(javax.servlet.ServletRequest

    servletRequest,javax.servlet.ServletResponse

    servletResponse,javax.servlet.FilterChain

    filterChain)

  throws java.io.IOException,

    javax.servlet.ServletException {

    String contentType =

      servletRequest.getContentType();

    if ((contentType == null) ||

      contentType.equalsIgnoreCase(

        "application/x-www-form-urlencoded"))     {

      translateParamsToAttributes(servletRequest,

        servletResponse);

    }

    filterChain.doFilter(servletRequest,

      servletResponse);

  }

  private void translateParamsToAttributes(

    ServletRequest request, ServletResponse response)

  {

    Enumeration paramNames =

        request.getParameterNames();

    while (paramNames.hasMoreElements())     {

      String paramName = (String)

          paramNames.nextElement();

      String [] values;

      values = request.getParameterValues(paramName);

      System.err.println("paramName = " + paramName);

      if (values.length == )

        request.setAttribute(paramName, values[]);

      else

        request.setAttribute(paramName, values);

    }

 }

}

 public class MultipartEncodeFilter extends

   BaseEncodeFilter {

   public MultipartEncodeFilter() { }

   public void doFilter(javax.servlet.ServletRequest

     servletRequest, javax.servlet.ServletResponse

     servletResponse,javax.servlet.FilterChain

     filterChain)

   throws java.io.IOException,

     javax.servlet.ServletException {

     String contentType =

       servletRequest.getContentType();

     // 只有当这个请求是多部分的时候才过滤这个请求编码

     if (contentType.startsWith(

                 "multipart/form-data")){

       try {

         String uploadFolder =

           getFilterConfig().getInitParameter(

               "UploadFolder");

         if (uploadFolder == null) uploadFolder = ".";

         /** The MultipartRequest class is:

         * Copyright (C) 2001 by Jason Hunter

         * <jhunter@servlets.com>. All rights reserved.

         **/

         MultipartRequest multi = new

           MultipartRequest(servletRequest,

                            uploadFolder,

                             *  *  );

         Enumeration params =

                  multi.getParameterNames();

         while (params.hasMoreElements()) {

           String name = (String)params.nextElement();

           String value = multi.getParameter(name);

           servletRequest.setAttribute(name, value);

         }

         Enumeration files = multi.getFileNames();

         while (files.hasMoreElements()) {

           String name = (String)files.nextElement();

           String filename = multi.getFilesystemName(name);

           String type = multi.getContentType(name);

           File f = multi.getFile(name);

          //在这一点上，做一些事情

           //文件，必要时

         }

       }

       catch (IOException e)

       {

         LogManager.logMessage(

           "error reading or saving file"+ e);//读取或保存文件错误

       }

     } // end if

     filterChain.doFilter(servletRequest,

                          servletResponse);

   } // end method doFilter()

 }