上传附件代码：借助commons-fileupload-1.2.jar

package com.str;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.util.Iterator;
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.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class UploadServlet extends HttpServlet {
 
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
   doGet(req, resp);
 }
 
 
 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  
  HttpServletRequest request = (HttpServletRequest)req; 
  HttpServletResponse response = (HttpServletResponse)resp; 
  
 /* response.setContentType("text/html;charset=gb2312");
  response.setCharacterEncoding("utf-8");*/
  
  OutputStream outputStream = null;   
  InputStream inputStream = null;
  
  DiskFileItemFactory factory = new DiskFileItemFactory(); 
  ServletFileUpload fileUpload = new ServletFileUpload(factory);
 
  try {
   List items = fileUpload.parseRequest(request); 
   for (Iterator iterator = items.iterator(); iterator.hasNext();) {   
    FileItem name = (FileItem) iterator.next();               
    if(!name.isFormField()){                     
     String fieldName  = name.getFieldName();  //这个是name值
     String fileName = name.getName();     //这个是全路径
     String lastFileName ="";
     
     //这句话获取的是源文件的原名称，不做任何修改
     String oldNamePath = fileName.substring(fileName.lastIndexOf("\\")+1);
     
     if(fileName.endsWith(".docx")|| fileName.endsWith(".xls")){
      
      lastFileName = request.getRealPath("/")+"\\upload\\"+ oldNamePath;
      outputStream = new FileOutputStream(new File(lastFileName )); 
      
      inputStream = name.getInputStream();                  
      byte[] bs = new byte[1024];                     
      int length = 0;                     
      while(null != inputStream && (length = inputStream.read(bs))!=-1){            
       outputStream.write(bs);    
      }  
     }
     outputStream.flush();
     }                            
    //把lastFileName存到数据库（这里就不写了不只lz用的什么方式）} 
   }
  } catch (Exception e) {
   e.printStackTrace();
  }

 }
}

单个下载文件，批量下载文件代码：借助于ant.jar包的ZipOutputStream、ZipEntry

package com.str;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

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

import org.apache.tools.zip.ZipEntry;
import org.apache.tools.zip.ZipOutputStream;

public class LoadServlet  extends HttpServlet {
 
 @Override
 /*protected void doGet(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  
  String path = getServletContext().getRealPath("/") + "\\upload";
  OutputStream o = resp.getOutputStream();
  byte b[] = new byte[1024];
  
  //这个地方的文件，可以从数据库中动态查找，我这边写死了为了简单展示
  File fileLoad = new File(path, "解析类型配置.xls");
  
  String filename = new String("解析类型配置.xls".getBytes("gbk"), "iso8859-1");

  System.out.println(filename);
  
  我记得在Excel导出数据的时候说过filename千万别写中文，其实经过以下：
  String filename = new String("解析类型配置.xls".getBytes("gbk"), "iso8859-1"); 
  转换以后，文件无论是中文、英文，都不会出现乱码情况，本人已验证
  
  resp.setHeader("Content-disposition", "attachment;filename="+ filename);
  
  long fileLength = fileLoad.length();    
  String length = String.valueOf(fileLength);   
  resp.setHeader("Content_Length", length);  
  FileInputStream in = new FileInputStream(fileLoad);      
  int n = 0;      
  while ((n = in.read(b)) != -1) {   
   o.write(b, 0, n);
   }
 }*/
 
 

//以上是单个下载附件，这边是批量压缩下载附件
 protected void doGet(HttpServletRequest req, HttpServletResponse resp)
 throws ServletException, IOException {
  
  String zipFileName = "test.zip";
  
  //这些文件都是存在的，我是写死了的，可以从页面传名称过来
  String[] filePathArray = {"1.jpg","2.jpg","3.xls","测试.docx"};   
  String path = getServletContext().getRealPath("/") + "\\image";
  
  resp.setContentType("application/x-msdownload" ); // 通知客户文件的MIME类型：
  resp.setHeader("Content-disposition","attachment;filename=" + zipFileName);
  
  ZipOutputStream zos = new ZipOutputStream(resp.getOutputStream());
  
  for (String filePath : filePathArray) {
   File file = new File(path + File.separator + filePath);
   doZip(file, zos);
  }   
  zos.close();
 }
 
 //处理批量下载时候，文件压缩问题
 private void doZip(File file, ZipOutputStream zos) throws IOException {
  if(file.exists()) {
   if (file.isFile()) {
    //如果是文件，写入到 zip 流中
    String fileName = file.getName();
    
    ZipEntry zet = new ZipEntry(file.getName());
    zos.putNextEntry(zet);
    FileInputStream fis = new FileInputStream(file);
    byte[] buffer = new byte[1024];
    int r = 0;
    while ((r = fis.read(buffer)) != -1) {
     zos.write(buffer, 0, r);
    }
    zos.setEncoding("gbk");   //这个地方很重要
    zos.flush();    
    fis.close();
   }else {
    System.out.println("不是文件，那就不下载了，因为前台会做处理，此处就不在一步步进行验证了!");
   }
  }
 }

}

java上传附件，批量下载附件(一)