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ZxingPlusJjwtSample

A demo application for generating QR code and scanning JJWT token.

using zxing-android-embedded and zxing for generating and scanning QR code.

Some Features of Zxing library:

  1. Can be used via Intents (little code required).
  2. Can be embedded in an Activity, for advanced customization of UI and logic.
  3. Scanning can be performed in landscape or portrait mode.
  4. Camera is managed in a background thread, for fast startup time.

JJWT aims to be the easiest to use and understand library for creating and verifying JSON Web Tokens (JWTs) on the JVM and Android.

JJWT is a pure Java implementation based exclusively on the JWT, JWS, JWE, JWK and JWA RFC specifications and open source under the terms of the Apache 2.0 License.

Usage

QR code generation

        val qrText = "Your qr code hash here"
        val multiFormatWriter = MultiFormatWriter()
        try {
            bitMatrix?.clear()
            val size = convertDpToPixel()
            bitMatrix = multiFormatWriter.encode(
                    qrText,
                    BarcodeFormat.QR_CODE,
                    size,
                    size
            )
            val barcodeEncoder = BarcodeEncoder()
            val bitmap = barcodeEncoder.createBitmap(bitMatrix)
            imageView.setImageBitmap(bitmap)
        } catch (e: WriterException) { //do nothing
        }

Decrypting JJWT token

        val publicKeyBytes = Base64.decode("your public key", Base64.DEFAULT)
        // create a key object from the bytes
        val keySpec =
            X509EncodedKeySpec(publicKeyBytes)
        val keyFactory = KeyFactory.getInstance("RSA")
        val publicKey = keyFactory.generatePublic(keySpec)
        return Jwts.parserBuilder().setSigningKey(publicKey).build().parseClaimsJws(jwtToken)

Scanning and Extracting result from QR code

        capture = CustomCaptureManager(this, barcodeScanner)
        capture?.setShowMissingCameraPermissionDialog(true)
        barcodeScanner.barcodeView.cameraSettings = camSettings
        capture?.setViewCaptureListener(this)
        capture?.initializeFromIntent(intent, savedInstanceState)
        capture?.decode()

In other lifecycle methods,add this-
 override fun onResume() {
        super.onResume()
        capture?.onResume()
    }

    override fun onPause() {
        super.onPause()
        capture?.onPause()
    }

    override fun onDestroy() {
        super.onDestroy()
        capture?.onDestroy()
    }

On getting the result,you can extract keys like this-

  //show your result here
        val claimsJws: Jws<Claims?>?
        try {
            claimsJws = decryptFile(json)
            //extract your keys from claimJws
            val stringKey = claimsJws?.body?.get("your key name", String::class.java)
            val intKey = claimsJws?.body?.get("your key name", Integer::class.java)
        } catch (e: Exception) {
            //handle exception
        }

Happy Coding!!