JWT verification using jjwt

Question

I generated a RSA key using keytool.

keytool -genkeypair -alias myAlias -keyalg RSA -dname ... 

creates a jks.

I am using this to sign..

String sig = Jwts.builder().setClaims(claims).setIssuedAt(new      
Date(now)).setExpiration(expires.getTime()).signWith(
SignatureAlgorithm.RS256, myKey).compact();

and for verifying..

Certificate cert = keystore.getCertificate(myAlias);
PublicKey publicKey = cert.getPublicKey();
Jwt jwt = Jwts.parser().setSigningKey(publicKey).require("user",  
"me").require("iotDevice", "123456789").parse(signature);

verifies fine.

I created a public key for this cert..

keytool -export -alias myAlias -keystore myKeyStore.jks -file myPem.pem
openssl rsa -in myPem.pem -pubout > myApp.pub

I am loading this public key to verify again..

RSAPublicKey getPublicKeyFromString(String key) throws IOException,  
GeneralSecurityException {
    String publicKey = key;
    publicKey = publicKey.replace("-----BEGIN PUBLIC KEY-----\n", "");
    publicKey = publicKey.replace("-----END PUBLIC KEY-----", "");
    publicKey = publicKey.replace("\n", "");
    byte[] encoded = Base64.getDecoder().decode(publicKey);
    KeyFactory kf = KeyFactory.getInstance("RSA");
    RSAPublicKey pubKey = (RSAPublicKey) kf.generatePublic(new 
    X509EncodedKeySpec(encoded));
    return pubKey;
}

PublicKey publicKey2 = getPublicKeyFromString(keyString); // keyString has myApp.pub
Jwt jwt = Jwts.parser().setSigningKey(publicKey2).require("user",  
"me").require("iotDevice", "123456789").parse(signature);

// fails with message

JWT signature does not match locally computed signature. JWT validity cannot be asserted and should not be trusted.

Any help is appreciated.

Thanks in advance