作者：whitefox
email: whitefox.jiang@corp.elong.com
日期：2000-7-6 11:32:15
來源水木清華

public class UploadServlet extends HttpServlet
{
  //default maximum allowable file size is 100k
  static final int MAX_SIZE = 102400;
  //instance variables to store root and success message
  String rootPath, successMessage;
  /**
   * init method is called when servlet is initialized.
   */
  public void init(ServletConfig config) throws ServletException
  {
    super.init(config);
    //get path in which to save file
    rootPath = config.getInitParameter("RootPath");
    if (rootPath == null)
    {
      rootPath = "/";
    }
    /*Get message to show when upload is complete. Used only if
      a success redirect page is not supplied.*/
    successMessage = config.getInitParameter("SuccessMessage");
    if (successMessage == null)
    {
      successMessage = "File upload complete!";
    }
  }
  /**
   * doPost reads the uploaded data from the request and writes
   * it to a file.
   */
  public void doPost(HttpServletRequest request,
    HttpServletResponse response)
  {
    ServletOutputStream out=null;
    DataInputStream in=null;
    FileOutputStream fileOut=null;
    try
    {
      /*set content type of response and get handle to output
        stream in case we are unable to redirect client*/
      response.setContentType("text/plain");
      out = response.getOutputStream();
    }
    catch (IOException e)
    {
      //print error message to standard out
      System.out.println("Error getting output stream.");
      System.out.println("Error description: " + e);
      return;
    }
    try
    {
      //get content type of client request
      String contentType = request.getContentType();
      //make sure content type is multipart/form-data
      if(contentType != null && contentType.indexOf(
        "multipart/form-data") != -1)
      {
        //open input stream from client to capture upload file
        in = new DataInputStream(request.getInputStream());
        //get length of content data
        int formDataLength = request.getContentLength();
        //allocate a byte array to store content data
        byte dataBytes[] = new byte[formDataLength];
        //read file into byte array
        int bytesRead = 0;
        int totalBytesRead = 0;
        int sizeCheck = 0;
        while (totalBytesRead < formDataLength)
        {
          //check for maximum file size violation
          sizeCheck = totalBytesRead + in.available();
          if (sizeCheck > MAX_SIZE)
          {
            out.println("Sorry, file is too large to upload.");
            return;
          }
          bytesRead = in.read(dataBytes, totalBytesRead,
            formDataLength);
          totalBytesRead += bytesRead;
        }
        //create string from byte array for easy manipulation
        String file = new String(dataBytes);
        //since byte array is stored in string, release memory
        dataBytes = null;
        /*get boundary value (boundary is a unique string that
          separates content data)*/
        int lastIndex = contentType.lastIndexOf("=");
        String boundary = contentType.substring(lastIndex+1,
          contentType.length());
        //get Directory web variable from request
        String directory="";
        if (file.indexOf("name=\"Directory\"") > 0)
        {
          directory = file.substring(
            file.indexOf("name=\"Directory\""));
          //remove carriage return
          directory = directory.substring(
            directory.indexOf("\n")+1);
          //remove carriage return
          directory = directory.substring(
            directory.indexOf("\n")+1);
          //get Directory
          directory = directory.substring(0,
            directory.indexOf("\n")-1);
          /*make sure user didn't select a directory higher in
            the directory tree*/
          if (directory.indexOf("..") > 0)
          {
            out.println("Security Error: You can't upload " +
              "to a directory higher in the directory tree.");
            return;
          }
        }
        //get SuccessPage web variable from request
        String successPage="";
        if (file.indexOf("name=\"SuccessPage\"") > 0)
        {
          successPage = file.substring(
            file.indexOf("name=\"SuccessPage\""));
          //remove carriage return
          successPage = successPage.substring(
            successPage.indexOf("\n")+1);
          //remove carriage return
          successPage = successPage.substring(
            successPage.indexOf("\n")+1);
          //get success page
          successPage = successPage.substring(0,
            successPage.indexOf("\n")-1);
        }
        //get OverWrite flag web variable from request
        String overWrite;
        if (file.indexOf("name=\"OverWrite\"") > 0)
        {
          overWrite = file.substring(
            file.indexOf("name=\"OverWrite\""));
          //remove carriage return
          overWrite = overWrite.substring(
            overWrite.indexOf("\n")+1);
          //remove carriage return
          overWrite = overWrite.substring(
            overWrite.indexOf("\n")+1);
          //get overwrite flag
          overWrite = overWrite.substring(0,
            overWrite.indexOf("\n")-1);
        }
        else
        {
          overWrite = "false";
        }
        //get OverWritePage web variable from request
        String overWritePage="";
        if (file.indexOf("name=\"OverWritePage\"") > 0)
        {
          overWritePage = file.substring(
            file.indexOf("name=\"OverWritePage\""));
          //remove carriage return
          overWritePage = overWritePage.substring(
            overWritePage.indexOf("\n")+1);
          //remove carriage return
          overWritePage = overWritePage.substring(
            overWritePage.indexOf("\n")+1);
          //get overwrite page
          overWritePage = overWritePage.substring(0,
            overWritePage.indexOf("\n")-1);
        }
        //get filename of upload file
        String saveFile = file.substring(
          file.indexOf("filename=\"")+10);
        saveFile = saveFile.substring(0,
          saveFile.indexOf("\n"));
        saveFile = saveFile.substring(
          saveFile.lastIndexOf("\\")+1,
          saveFile.indexOf("\""));
        /*remove boundary markers and other multipart/form-data
          tags from beginning of upload file section*/
        int pos; //position in upload file
        //find position of upload file section of request
        pos = file.indexOf("filename=\"");
        //find position of content-disposition line
        pos = file.indexOf("\n",pos)+1;
        //find position of content-type line
        pos = file.indexOf("\n",pos)+1;
        //find position of blank line
        pos = file.indexOf("\n",pos)+1;
        /*find the location of the next boundary marker
          (marking the end of the upload file data)*/
        int boundaryLocation = file.indexOf(boundary,pos)-4;
        //upload file lies between pos and boundaryLocation
        file = file.substring(pos,boundaryLocation);
        //build the full path of the upload file
        String fileName = new String(rootPath + directory +
          saveFile);
        //create File object to check for existence of file
        File checkFile = new File(fileName);
        if (checkFile.exists())
        {
          /*file exists, if OverWrite flag is off, give
            message and abort*/
          if (!overWrite.toLowerCase().equals("true"))
          {
            if (overWritePage.equals(""))
            {
              /*OverWrite HTML page URL not received, respond
                with generic message*/
              out.println("Sorry, file already exists.");
            }
            else
            {
              //redirect client to OverWrite HTML page
              response.sendRedirect(overWritePage);
            }
            return;
          }
        }
        /*create File object to check for existence of
          Directory*/
        File fileDir = new File(rootPath + directory);
        if (!fileDir.exists())
        {
          //Directory doesn't exist, create it
          fileDir.mkdirs();
        }
        //instantiate file output stream
        fileOut = new FileOutputStream(fileName);
        //write the string to the file as a byte array
        fileOut.write(file.getBytes(),0,file.length());
        if (successPage.equals(""))
        {
          /*success HTML page URL not received, respond with
            generic success message*/
          out.println(successMessage);
          out.println("File written to: " + fileName);
        }
        else
        {
          //redirect client to success HTML page
          response.sendRedirect(successPage);
        }
      }
      else //request is not multipart/form-data
      {
        //send error message to client
        out.println("Request not multipart/form-data.");
      }
    }
    catch(Exception e)
    {
      try
      {
        //print error message to standard out
        System.out.println("Error in doPost: " + e);
        //send error message to client
        out.println("An unexpected error has occurred.");
        out.println("Error description: " + e);
      }
      catch (Exception f) {}
    }
    finally
    {
      try
      {
        fileOut.close(); //close file output stream
      }
      catch (Exception f) {}
      try
      {
        in.close(); //close input stream from client
      }
      catch (Exception f) {}
      try
      {
        out.close(); //close output stream to client
      }
      catch (Exception f) {}
    }
  }
}