Generating VAPID Keys

[MathikumarC]

Hi,

Your libs are excellent to learn for web push in java.

My requirement is sending push messages without GCM ,FCM ,etc... Without application server key when i try to subscribe in client side i am getting below error message.

app.js:57 Unable to register service worker. DOMException: Registration failed - missing applicationServerKey, and manifest empty or missing

So I have generated VAPID keys using below code and output as follows.

 ECNamedCurveParameterSpec parameterSpec = 
 ECNamedCurveTable.getParameterSpec("prime256v1");
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("ECDH", "BC");
        keyPairGenerator.initialize(parameterSpec);
        KeyPair serverKey = keyPairGenerator.generateKeyPair();
        
        PrivateKey priv = serverKey.getPrivate();
        PublicKey pub = serverKey.getPublic();

Below is my public and private keys:

EC Private Key
S: 84d0fbbda6e65e29b4ef314fb502879da07581280b3059cb8e8ef41b28099d5b

EC Public Key
X: 171874128880f91dea2daf4514e5bcf7020c86da1abf063d389149392c0812ff
Y: 175edbd04506da58581b72c28cd4833d4f104c7cc2b5300416ee547c5d7bd9d4

How do i pass my public key to PushManager.subscribe method.

Can you please help me out on this.

Thanks in advance.

[martijndwars]

Did you read this document? It explains how to generate a keypair using openssl, how to encode the public key for use in your frontend (i.e. for PushManager.subscribe), and how to load it into your Java application that uses this library.

[MathikumarC]

@martijndwars R Thanks for the prompt reply. It is working perfectly when i generate VAPID keys using openssl :-) . But in my use case i need generate VAPID keys in java then subscribe with public key which i generated in java and push messages from my application server using java.

[martijndwars]

Ah, right. In that case, you can use Utils.savePublicKey to convert your Java-generated PublicKey to a byte[]. This byte[] is then passed to the PushManager.subscribe method.

It may be more convenient to base64 encode the byte[] in Java and base64 decode the string in JavaScript. For example, after generating the keypair in Java:

KeyPair keyPair = generateKeyPair();
byte[] publicKey = Utils.savePublicKey((ECPublicKey) keyPair.getPublic());
String publicKeyBase64 = BaseEncoding.base64Url().encode(publicKey);
System.out.println("PublicKey = " + publicKeyBase64);
// PublicKey = BPf36QAqZNNvvnl9kkpTDerXUOt6Nm6P4x9GEvmFVFKgVyCVWy24KUTs6wLQtbV2Ug81utbNnx86_vZzXDyrl88=

Then in JavaScript:

function subscribe() {
    const publicKey = base64UrlToUint8Array('BPf36QAqZNNvvnl9kkpTDerXUOt6Nm6P4x9GEvmFVFKgVyCVWy24KUTs6wLQtbV2Ug81utbNnx86_vZzXDyrl88=');
    
    navigator.serviceWorker.ready.then(function (serviceWorkerRegistration) {
        serviceWorkerRegistration.pushManager.subscribe({
            userVisibleOnly: true,
            applicationServerKey: publicKey
        })
        .then(function (subscription) {
            return sendSubscriptionToServer(subscription);
        })
        .catch(function (e) {
            if (Notification.permission === 'denied') {
                console.warn('Permission for Notifications was denied');
            } else {
                console.error('Unable to subscribe to push.', e);
            }
        });
    });
}

function base64UrlToUint8Array(base64UrlData) {
    const padding = '='.repeat((4 - base64UrlData.length % 4) % 4);
    const base64 = (base64UrlData + padding)
        .replace(/\-/g, '+')
        .replace(/_/g, '/');

    const rawData = atob(base64);
    const buffer = new Uint8Array(rawData.length);
    
    for (let i = 0; i < rawData.length; ++i) {
        buffer[i] = rawData.charCodeAt(i);
    }
    
    return buffer;
}

[MathikumarC]

Great!!!!. It is working exactly what i have expected.

Thanks a lot.

Regards
Mathikumar