文件上传

实现文件的上传的第一种方式

（经过servlet实现文件的上传）

1:文件的上传（以上传图片为例）

Jsp代码：

<form action="UploadServlet" method="post"enctype="multipart/

form-data">

上传文件:<input type="file" name="file1"><br>

上传文件:<input type="file" name="file2"><br>

上传文件:<input type="file" name="file3"><br>

     ${result};//显示上传结果

<input type="submit" value="提交">

</form><hr>

Servlet代码：

public class UploadServlet extends HttpServlet {

  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

     doPost(req,resp);

  }

  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    System.out.println("已接收到请求");

  //从request当中获取流信息

       InputStream fileSource = req.getInputStream();

String tempFileName = "E:/tempFile”;

       //tempFile指向临时文件

       File tempFile = new File(tempFileName);

       //outputStram文件输出流指向这个临时文件

       FileOutputStream outStream = new FileOutputStream(tempFile);

       byte b[] = new byte[1024];

       int n;

       while(( n = fileSource.read(b)) != -1){

         outStream.write(b, 0, n);

       }

       //关闭输出流、输入流

       outputStream.close();

       fileSource.close();

      

       //获取上传文件的名称

       RandomAccessFile randomFile = new RandomAccessFile(tempFile,"r");

       randomFile.readLine();//读取临时文件的第一行

       String str = randomFile.readLine();//读取临时文件的第二行 

//不一样的浏览器下读取文件的名称的方法不同，能够用httpwatch肯定

       int begin = str.lastIndexOf("\\") + 1;

       int end = str.lastIndexOf("\"");

       String filename = str.substring(begin, end);

       System.out.println("filename:" + filename);

      

       //从新定位文件指针到文件头

       randomFile.seek(0);

       long startPosition = 0;

       int i = 1;

       //获取文件内容 开始位置

       while(( n = randomFile.readByte()) != -1 && i <=4){

         if(n == '\n'){

            startPosition = randomFile.getFilePointer();

            i ++;

         }

       }

       startPosition = randomFile.getFilePointer() -1;

       //获取文件内容 结束位置

       randomFile.seek(randomFile.length());

       long endPosition = randomFile.getFilePointer();

       int j = 1;

       while(endPosition >=0 && j<=2){

         endPosition--;

         randomFile.seek(endPosition);

         if(randomFile.readByte() == '\n'){

            j++;

         }

       }

       endPosition = endPosition -1;

      

       //设置保存上传文件的路径

       String realPath = getServletContext().getRealPath("/") + "images";

       File fileupload = new File(realPath);

       if(!fileupload.exists()){

         fileupload.mkdir();

       }

       File saveFile = new File(realPath,filename);

       RandomAccessFile randomAccessFile = new RandomAccessFile(saveFile,"rw");

       //从临时文件当中读取文件内容（根据起止位置获取）

       randomFile.seek(startPosition);

       while(startPosition < endPosition){

         randomAccessFile.write(randomFile.readByte());

         startPosition = randomFile.getFilePointer();

       }

       //关闭输入输出流、删除临时文件

       randomAccessFile.close();

       randomFile.close();

       tempFile.delete();

      

       req.setAttribute("result", "上传成功！");

       RequestDispatcher dispatcher = req.getRequestDispatcher("index.jsp");

       dispatcher.forward(req, resp);

     }

}

2文件的下载

1：jsp代码

   下载：(txt.txt已放到images目录下)

<a href="download.do?filename=text.txt">text.txt</a>${erro}

Servlet代码：

public class Download extends HttpServlet {

  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

       String path=getServletContext().getRealPath("/")+"images/";

       String filename=req.getParameter("filename");

       File file=new File(path+filename);

       if(file.exists()){

     //设置相应类型application/octet-stream

       resp.setContentType("application/x-msdownload");

       //设置头信息

       resp.setHeader("Content-Disposition", "attachment;filename=\"" + filename + "\"");

       InputStream inputStream = new FileInputStream(file);

       ServletOutputStream ouputStream = resp.getOutputStream();

       byte b[] = new byte[1024];

       int n ;

       while((n = inputStream.read(b)) != -1){

         ouputStream.write(b,0,n);

       }

       //关闭流、释放资源

       ouputStream.close();

       inputStream.close();

     

     

     }

       else{

       req.setAttribute("erro", "文件不存在，下载失败！");

       RequestDispatcher dis=req.getRequestDispatcher("index.jsp");

       dis.forward(req, resp);

       }

  }

  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

     doGet(req, resp);

  }

 

}

《web.xml文件生成，注意action与url-pattern 一致》