Question

I have developed an signed applet that is used to upload a file in encrypted form.
This applet I am calling from jsp which is working fine, but my issue is :
Can I call that applet from jsp in such way that will return encrypted file in jsp and I pass that file to server side?
And Can I create multipart file in applet or jsp for that encrypted file and send it to server?

My running Applet looks like:

public static void encryptDecryptFile(String srcFileName,
            String destFileName, Key key, int cipherMode) throws Exception {
        OutputStream outputWriter = null;
        InputStream inputReader = null;     
        try {                   
            Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");         
            byte[] buf = cipherMode == Cipher.ENCRYPT_MODE ? new byte[100]
                    : new byte[128];
            int bufl;
            cipher.init(cipherMode, key);           
            outputWriter = new FileOutputStream(destFileName);
            inputReader = new FileInputStream(srcFileName);
            while ((bufl = inputReader.read(buf)) != -1) {          
                byte[] encText = null;
                if (cipherMode == Cipher.ENCRYPT_MODE)
                    encText = encrypt(copyBytes(buf, bufl), (PublicKey) key);
                else
                    encText = decrypt(copyBytes(buf, bufl), (PrivateKey) key);              
                outputWriter.write(encText);
            }           
        } catch (Exception e) {e.printStackTrace();
            throw e;
        } finally {
            try {
                if (outputWriter != null)
                    outputWriter.close();
                if (inputReader != null)
                    inputReader.close();
            } catch (Exception e) {
            }
        }
    }

My Calling jsp looks like :

<applet id="upload" name="upload" code="TestApplet.class" archive="Encrypt.jar" width="360" height="350"></applet>

Answer 1

The easiest way would be using HttpClient Apache Commons library. You will have to do something like this in your applet:

    public void sendFile throws IOException {
        HttpClient client = new HttpClient();
        PostMethod postMethod = new PostMethod("http://yourserverip:8080/yourServlet");

        File f = new File(destFileName);
       
        postMethod.setRequestBody(new FileInputStream(f));
        postMethod.setRequestHeader("Content-type",
            "text/xml; charset=ISO-8859-1");

        client.executeMethod(postMethod);
        postMethod.releaseConnection();
    }

This will trigger your servlet doPost() method where you can retrieve the file. As you said, your applet should be signed to be allowed to do this.