基于Java文件输入输出流实现文件上传下载功能

 
 

 

  
请选择上传文件:

  

 
 
${info}
 
 
 
  文件下载：${filename}

@WebServlet("/FileUpServlet")
public class FileUpServlet extends HttpServlet {
 private static final long serialVersiOnUID= 1L;
  
 /**
  * @see HttpServlet#HttpServlet()
  */
 public FileUpServlet() {
  super();
  // TODO Auto-generated constructor stub
 }

 /**
  * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
  */
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  // TODO Auto-generated method stub
  doPost(request, response);
 }

 /**
  * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
  */
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  // TODO Auto-generated method stub
  request.setCharacterEncoding("utf-8");
  InputStream filesource = request.getInputStream();//request获取流信息
  String tempname = "D:/temp";//tempfile代表临时存放文件
  File tempfile = new File(tempname);//创建临时文件
  
  FileOutputStream outputStream = new FileOutputStream(tempfile);//输出流对象，指定输出指tempfile目录下
  byte b[] = new byte[1024];
  int n;
  while((n = filesource.read(b))!= -1)//从输出流中每次读取1024字节,直至读完
  {
   outputStream.write(b,0,n);
  }
  outputStream.close();
  filesource.close();//关闭输入输出流
  
  
  /*以下为具体的文件操作，主要为解析临时产生的 temp文件 ，知识多为java输入输出流的内容！*/
  

  RandomAccessFile randomfile = new RandomAccessFile(tempfile, "r");//随机流，指定要读临时文件，只读
  randomfile.readLine();//读取第一行,无效数据，不需要
  String str = randomfile.readLine();//读取第二行
  int beginIndex = str.lastIndexOf("=")+2;//指定所需数据的开始位置
  int endIndex = str.lastIndexOf("\"");//指定所需数据截至位置
  String filename = str.substring(beginIndex,endIndex);//截取文件名
  
  //重新定位文件指针，获取文件内容
  randomfile.seek(0);//文件指针从头开始
  long startext = 0;
  int i = 1;
  //文件内容开始位置
  while((n=randomfile.readByte()) != -1&&i <= 4)
  {
   if(n=='\n')
   {
    startext = randomfile.getFilePointer();
    i++;
   } 
  }
  startext = randomfile.getFilePointer() - 1;
  //获取文件内容 结束位置
  randomfile.seek(randomfile.length());
  long endtext = randomfile.getFilePointer();
  int j = 1;
  while(endtext >= 0 && j <= 2)
  {
   endtext--;
   randomfile.seek(endtext);
   if(randomfile.readByte()=='\n')
   {
    j++;
   }
  }
  endtext = endtext-1;
  
  //将临时文件保存至指定目录中 
  String realpath = getServletContext().getRealPath("/")+"images";//设置文件保存目录
  System.out.println(realpath);
  File fileupload = new File(realpath);
  if(!fileupload.exists())
  {
   fileupload.mkdir();//目录不存在则创建
  }
  File savefile = new File(realpath,filename);
  RandomAccessFile randomAccessFile = new RandomAccessFile(savefile, "rw");
  randomfile.seek(startext);
  while(startext

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  // TODO Auto-generated method stub
  String filename = request.getParameter("filename");
  String path = getServletContext().getRealPath("/")+"images/";
  File file = new File(path+filename);//找到文件
  if(file.exists())
  {
   response.setContentType("application/x-msdownload"); //设置响应类型,此处为下载类型
   response.setHeader("Content-Disposition", "attachment;filename=\""+filename+"\"");//以附件的形式打开
   InputStream inputStream = new FileInputStream(file);
   ServletOutputStream outputStream = response.getOutputStream();
   byte b[] = new byte[1024];
   int n;
   while((n = inputStream.read(b)) != -1)
   {
    outputStream.write(b,0,n);
   }
   outputStream.close();
   inputStream.close();   
   }else{
   request.setAttribute("result", "文件不存在！下载失败！");
   request.getRequestDispatcher("/fildeOp.jsp").forward(request, response);
  }
 }