import java.io.File;
import java.io.IOException;
import java.util.List;

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.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**
 * 上传附件
 * @author new
 *
 */
public class UploadAnnexServlet extends HttpServlet {

 private static String path = "";

 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

 doPost(request, response);
 }

 /*
 * post处理
 * (non-Javadoc)
 * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
 */
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

 path = this.getServletContext().getRealPath("/upload");

 try {
 DiskFileItemFactory factory = new DiskFileItemFactory();
 ServletFileUpload up = new ServletFileUpload(factory);
 List<FileItem> ls = up.parseRequest(request);

 for (FileItem fileItem : ls) {
 if (fileItem.isFormField()) {
  String FieldName = fileItem.getFieldName();
  //getName()返回的是文件名字 普通域没有文件 返回NULL
  //     String Name = fileItem.getName();
  String Content = fileItem.getString("gbk");
  request.setAttribute(FieldName, Content);
 } else {
 
  String nm = fileItem.getName().substring(
  fileItem.getName().lastIndexOf("\\") + 1);
  File mkr = new File(path, nm);
  if (mkr.createNewFile()) {
  fileItem.write(mkr);//非常方便的方法
  }
  request.setAttribute("result", "上传文件成功！");
 }
 }
 } catch (Exception e) {
 e.printStackTrace();
 request.setAttribute("result", "上传失败，请查找原因，重新再试！");
 }
 request.getRequestDispatcher("/pages/admin/annex-manager.jsp").forward(
 request, response);
 }

}

import java.io.IOException;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 下载文件
 * @author
 *
 */
public class DownloadFilesServlet extends HttpServlet {

 /**
 * 
 */
 private static final long serialVersionUID = 8594448765428224944L;

 public void doGet(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

 doPost(request, response);
 }

 /*
 * 处理请求
 * (non-Javadoc)
 * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
 */
 public void doPost(HttpServletRequest request, HttpServletResponse response)
 throws ServletException, IOException {

 String name = request.getParameter("fileName");

 System.out.print("dddddddddd:" + name);
 // web绝对路径
 String path = request.getSession().getServletContext().getRealPath("/");
 String savePath = path + "upload";

 // 设置为下载application/x-download
 response.setContentType("application/x-download");
 // 即将下载的文件在服务器上的绝对路径
 String filenamedownload = savePath + "/" + name;
 // 下载文件时显示的文件保存名称
 String filenamedisplay = name;
 // 中文编码转换
 filenamedisplay = URLEncoder.encode(filenamedisplay, "UTF-8");
 response.addHeader("Content-Disposition", "attachment;filename="
 + filenamedisplay);
 try {
 java.io.OutputStream os = response.getOutputStream();
 java.io.FileInputStream fis = new java.io.FileInputStream(
  filenamedownload);
 byte[] b = new byte[1024];
 int i = 0;
 while ((i = fis.read(b)) > 0) {
 os.write(b, 0, i);
 }
 fis.close();
 os.flush();
 os.close();
 } catch (Exception e) {

 }

 }

}