Question

I have been trying to upload a file to a Tomcat server through a servlet, but without success. I am able to create a directory, but somehow the servlet code is not creating a file inside the “upload” directory.

Java code in Android:

 public void upLoad()
{


     String exsistingFileName = path+"//"+"test123.txt";

     String lineEnd = "\r\n";
     String twoHyphens = "--";
     String boundary = "*****";
     try {
         // ------------------ CLIENT REQUEST

         Log.e(Tag, "Inside second Method");

         FileInputStream fileInputStream = new FileInputStream(new File(
                 exsistingFileName));

         // open a URL connection to the Servlet

         URL url = new URL(urlString);

         // Open a HTTP connection to the URL

         conn = (HttpURLConnection) url.openConnection();

         // Allow Inputs
         conn.setDoInput(true);

         // Allow Outputs
         conn.setDoOutput(true);

         // Don't use a cached copy.
         conn.setUseCaches(false);

         // Use a post method.
         conn.setRequestMethod("POST");

         conn.setRequestProperty("Connection", "Keep-Alive");

         conn.setRequestProperty("Content-Type",
                "multipart/form-data;boundary=" + boundary);


         DataOutputStream dos = new DataOutputStream(conn.getOutputStream());

         dos.writeBytes(twoHyphens + boundary + lineEnd);
         dos.writeBytes("Content-Disposition: post-data; name=uploadedfile;filename="
                         + exsistingFileName + "" + lineEnd);
         dos.writeBytes(lineEnd);

         Log.e(Tag, "Headers are written");

         // create a buffer of maximum size

         int bytesAvailable = fileInputStream.available();
         int maxBufferSize = 1000;
         // int bufferSize = Math.min(bytesAvailable, maxBufferSize);
         byte[] buffer = new byte[bytesAvailable];

         // read file and write it into form...

         int bytesRead = fileInputStream.read(buffer, 0, bytesAvailable);

         while (bytesRead > 0) {
             dos.write(buffer, 0, bytesAvailable);
             bytesAvailable = fileInputStream.available();
             bytesAvailable = Math.min(bytesAvailable, maxBufferSize);
             bytesRead = fileInputStream.read(buffer, 0, bytesAvailable);
         }

         // send multipart form data necesssary after file data...

         dos.writeBytes(lineEnd);
         dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

         // close streams
         Log.e(Tag, "File is written");
         fileInputStream.close();
         dos.flush();
         dos.close();

     } catch (MalformedURLException ex) {
         Log.e(Tag, "error: " + ex.getMessage(), ex);
     }

     catch (IOException ioe) {
         Log.e(Tag, "error: " + ioe.getMessage(), ioe);
     }

     try {
         BufferedReader rd = new BufferedReader(new InputStreamReader(conn
                 .getInputStream()));
         String line;
         while ((line = rd.readLine()) != null) {
             Log.e("Dialoge Box", "Message: " + line);
         }
         rd.close();

     } catch (IOException ioex) {
         Log.e("MediaPlayer", "error: " + ioex.getMessage(), ioex);
     }
}

Servlet code on Tomcat server:

import java.io.File;
import java.io.IOException;
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.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

/**
* Servlet implementation class UploadServlet
*/
public class UploadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

private static final String UPLOAD_DIRECTORY = "upload";
private static final int THRESHOLD_SIZE = 1024 * 1024 * 3; // 3MB
private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB
private static final int REQUEST_SIZE = 1024 * 1024 * 50; // 50MB

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
 *      response)
 */
 protected void doPost(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {
    // checks if the request actually contains upload file
    if (!ServletFileUpload.isMultipartContent(request)) {
        // if not, we stop here
        return;
    }

    // configures some settings
    DiskFileItemFactory factory = new DiskFileItemFactory();
    factory.setSizeThreshold(THRESHOLD_SIZE);
    factory.setRepository(new File(System.getProperty("java.io.tmpdir")));

    ServletFileUpload upload = new ServletFileUpload(factory);
    upload.setFileSizeMax(MAX_FILE_SIZE);
    upload.setSizeMax(REQUEST_SIZE);

    // constructs the directory path to store upload file
    String uploadPath = getServletContext().getRealPath("")
        + File.separator + UPLOAD_DIRECTORY;
    // creates the directory if it does not exist
    File uploadDir = new File(uploadPath);
    if (!uploadDir.exists()) {
        uploadDir.mkdir();   //I can see the created directory...but nothing happens after that....No error message display after creating directory
    }

    try {
        // parses the request's content to extract file data
        List formItems = upload.parseRequest(request);
        Iterator iter = formItems.iterator();

        // iterates over form's fields
        while (iter.hasNext()) {
            FileItem item = (FileItem) iter.next();
            // processes only fields that are not form fields
            if (!item.isFormField()) {
                String fileName = new File(item.getName()).getName();
                String filePath = uploadPath + File.separator + fileName;
                File storeFile = new File(filePath);

                // saves the file on disk
                item.write(storeFile);
            }
        }
        request.setAttribute("message", "Upload has been done successfully!");
    } catch (Exception ex) {
        request.setAttribute("message", "There was an error: " + ex.getMessage());
    }
    getServletContext().getRequestDispatcher("/message.jsp").forward(request,         response);
 }
}

My file structure on the server is:

/webapps/
   demo/
      upload/ - The file I'm trying to create (test123.txt) should be inside this folder, but it's not.
   WEB-INF/
      classes/ - UploadServlet.class
      lib/ - commons IO and upload jars

Answer 1

Your Content-Disposition header is wrong. It says post-data while it has to be form-data in case of multipart/form-data. Fix it accordingly in your client:

dos.writeBytes("Content-Disposition: form-data; name=uploadedfile;filename="
                     + exsistingFileName + "" + lineEnd);

See also:

• Using java.net.URLConnection to fire and handle HTTP requests

---

Unrelated to the concrete problem, storing uploaded files in the webapp’s deploy folder is absolutely a bad idea. They’ll all get lost whenever you redeploy a new version of the webapp, with the simple reason that all those so far uploaded files are for sure not contained in the original WAR. Store them somewhere else outside the deploy folder. Just do not ever use getRealPath(), it’ll only lead to poor practices.

Further, FileInputStream#available() absolutely doesn’t do what you thought there in your code. Get rid of it and just do the usual read-write in a for loop with a fixed buffer size, e.g. 10KB.

Also, using DataOutputStream here is scary. It serves a different purpose (creating .dat files) and in this particular construct there’s a big risk for character encoding related issues. Just use PrintWriter which you wrap around OutputStreamWriter with a specified charset. Note that a complete example is shown in the above “See also” link.