servlet上传下载

package utils.imgUpload;
import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import java.util.UUID; 
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; 
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload; @SuppressWarnings("serial")
public class ImgUpload extends HttpServlet {
    /*
     /imgUpload/ImgUpload
     */
@SuppressWarnings("unchecked")
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
    System.out.println(request.getAttribute("name"));
    System.out.println(request.getParameter("name"));
    String savePath = this.getServletConfig().getServletContext().getRealPath("");
    savePath = savePath + "/uploads/";
File f1 = new File(savePath);
System.out.println(savePath);
if (!f1.exists()) {
f1.mkdirs();
     }
DiskFileItemFactory fac = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(fac);
upload.setHeaderEncoding("utf-8");
//upload.setFileSizeMax(fileSizeMax);设置文件最大值
List fileList = null;
    try {
        //解析请求正文，获取上传文件，不抛出异常则写入真是路径 
         fileList = upload.parseRequest(request);
         } catch (FileUploadException ex) {
        return;
        }
Iterator<FileItem> it = fileList.iterator();
String name = "";
String extName = "";
while (it.hasNext()) {
FileItem item = it.next();
if (!item.isFormField()) {
name = item.getName();
long size = item.getSize();
String type = item.getContentType();
System.out.println(size + " " + type);
     if (name == null || name.trim().equals("")) {
     continue;
     }
    if (name.lastIndexOf(".") >= 0) {
    extName = name.substring(name.lastIndexOf("."));
    }
File file = null;
    do {
         name = UUID.randomUUID().toString();
        file = new File(savePath + name + extName);
        } while (file.exists());
       File saveFile = new File(savePath + name + extName);
       try {
      item.write(saveFile);
      } catch (Exception e) {
      e.printStackTrace();
           }
           }
           }
     response.getWriter().print(name + extName);
    }
}