显示上传的文件，图片则显示，附件则提供下载
package cn.com.leadfar.cms.backend.view;import java.io.File;import java.io.IOException;import java.net.URLDecoder;import java.net.URLEncoder;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.apache.commons.io.FileUtils;import cn.com.leadfar.cms.backend.model.Attachment;public class AttachmentFilter implements Filter {@Overridepublic void destroy() {}@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {//判断请求的URI，是否包含"upload_image"//如果包含"upload_image"，则从d:/temp/upload目录中读取相应的文件，并且把文件的数据流写入responseHttpServletRequest req = (HttpServletRequest)request;HttpServletResponse resp = (HttpServletResponse)response;String requestURI = req.getRequestURI();//因为路径中可能包含有经过编码的信息，所以需要将它转换为正确的字符串requestURI = URLDecoder.decode(requestURI, request.getCharacterEncoding());//indexOf返回值：//-1表示不包含这个字符串//某个值，就表示这个字符串起始字符的索引//requestURI的值，可能是：/cms/backend/upload_image/logo.gifint index = requestURI.indexOf("/upload_image/");if(index != -1){ String imageName = requestURI.substring(index+"/upload_image/".length());byte[] image = FileUtils.readFileToByteArray(new File(Attachment.ATTACHMENT_DIR+imageName));response.setContentType("image/jpeg");response.getOutputStream().write(image);return;}index = requestURI.indexOf("/upload_file/");if(index != -1){String fileName = requestURI.substring(index+"/upload_file/".length());byte[] file = FileUtils.readFileToByteArray(new File(Attachment.ATTACHMENT_DIR+fileName));response.setContentType("application/x-msdownload");response.getOutputStream().write(file);return;}//让其他的请求通行！chain.doFilter(request, response);}@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}}?