JWT Token gneration for apple Sign in verification

JWTToken.java

/***Imports ****/
import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
import org.bouncycastle.openssl.PEMParser;
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
import java.security.PrivateKey;
import java.security.PublicKey;
import io.jsonwebtoken.JwsHeader;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import java.util.Date;
import java.io.File;
import org.springframework.util.ResourceUtils;
/**************/

/***
* To generate JWT token for verification
* @param identifierFromApp the service identifier of web app or kid from mobile app extracted from id token
*
****/
private String generateJWT(String identiferFromApp) throws Exception {
        // Generate a private key for token verification from your end with your creds
        PrivateKey pKey = generatePrivateKey();
        String token = Jwts.builder()
                .setHeaderParam(JwsHeader.KEY_ID, appleKeyId)
                .setIssuer(appleTeamId)
                .setAudience("https://appleid.apple.com")
                 .setSubject(identiferFromApp)
                .setExpiration(new Date(System.currentTimeMillis() + (1000 * 60 * 5)))
                .setIssuedAt(new Date(System.currentTimeMillis()))
                .signWith(pKey, SignatureAlgorithm.ES256)
                 .compact();
        return token;
    }

// Method to generate private key from certificate you created
    private PrivateKey generatePrivateKey() throws Exception {
        // here i have added cert at resource/apple folder. So if you have added somewhere else, just replace it with your path ofcert
        File file = ResourceUtils.getFile("classpath:apple/cert.p8");
        final PEMParser pemParser = new PEMParser(new FileReader(file));
        final JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
        final PrivateKeyInfo object = (PrivateKeyInfo) pemParser.readObject();
        final PrivateKey pKey = converter.getPrivateKey(object);
        pemParser.close();
        return pKey;
    }