//
    // JSON Web Token is a compact URL-safe means of representing claims/attributes to be transferred between two parties.
    // This example demonstrates producing and consuming a signed JWT
    //

    // Generate an RSA key pair, which will be used for signing and verification of the JWT, wrapped in a JWK
    RsaJsonWebKey rsaJsonWebKey = RsaJwkGenerator.generateJwk(2048);

    // Give the JWK a Key ID (kid), which is just the polite thing to do
    rsaJsonWebKey.setKeyId("k1");

    // Create the Claims, which will be the content of the JWT
    JwtClaims claims = new JwtClaims();
    claims.setIssuer("Issuer");  // who creates the token and signs it
    claims.setAudience("Audience"); // to whom the token is intended to be sent
    claims.setExpirationTimeMinutesInTheFuture(10); // time when the token will expire (10 minutes from now)
    claims.setGeneratedJwtId(); // a unique identifier for the token
    claims.setIssuedAtToNow();  // when the token was issued/created (now)
    claims.setNotBeforeMinutesInThePast(2); // time before which the token is not yet valid (2 minutes ago)
    claims.setSubject("subject"); // the subject/principal is whom the token is about
    claims.setClaim("email","mail@example.com"); // additional claims/attributes about the subject can be added
    List<String> groups = Arrays.asList("group-one", "other-group", "group-three");
    claims.setStringListClaim("groups", groups); // multi-valued claims work too and will end up as a JSON array

    // A JWT is a JWS and/or a JWE with JSON claims as the payload.
    // In this example it is a JWS so we create a JsonWebSignature object.
    JsonWebSignature jws = new JsonWebSignature();

    // The payload of the JWS is JSON content of the JWT Claims
    jws.setPayload(claims.toJson());

    // The JWT is signed using the private key
    jws.setKey(rsaJsonWebKey.getPrivateKey());

    // Set the Key ID (kid) header because it's just the polite thing to do.
    // We only have one key in this example but a using a Key ID helps
    // facilitate a smooth key rollover process
    jws.setKeyIdHeaderValue(rsaJsonWebKey.getKeyId());

    // Set the signature algorithm on the JWT/JWS that will integrity protect the claims
    jws.setAlgorithmHeaderValue(AlgorithmIdentifiers.RSA_USING_SHA256);

    // Sign the JWS and produce the compact serialization or the complete JWT/JWS
    // representation, which is a string consisting of three dot ('.') separated
    // base64url-encoded parts in the form Header.Payload.Signature
    // If you wanted to encrypt it, you can simply set this jwt as the payload
    // of a JsonWebEncryption object and set the cty (Content Type) header to "jwt".
    String jwt = jws.getCompactSerialization();


    // Now you can do something with the JWT. Like send it to some other party
    // over the clouds and through the interwebs.
    System.out.println("JWT: " + jwt);


    // Use JwtConsumerBuilder to construct an appropriate JwtConsumer, which will
    // be used to validate and process the JWT.
    // The specific validation requirements for a JWT are context dependent, however,
    // it typically advisable to require a (reasonable) expiration time, a trusted issuer, and
    // and audience that identifies your system as the intended recipient.
    // If the JWT is encrypted too, you need only provide a decryption key or
    // decryption key resolver to the builder.
    JwtConsumer jwtConsumer = new JwtConsumerBuilder()
            .setRequireExpirationTime() // the JWT must have an expiration time
            .setMaxFutureValidityInMinutes(300) // but the  expiration time can't be too crazy
            .setAllowedClockSkewInSeconds(30) // allow some leeway in validating time based claims to account for clock skew
            .setRequireSubject() // the JWT must have a subject claim
            .setExpectedIssuer("Issuer") // whom the JWT needs to have been issued by
            .setExpectedAudience("Audience") // to whom the JWT is intended for
            .setVerificationKey(rsaJsonWebKey.getKey()) // verify the signature with the public key
            .build(); // create the JwtConsumer instance

    try
    {
        //  Validate the JWT and process it to the Claims
        JwtClaims jwtClaims = jwtConsumer.processToClaims(jwt);
        System.out.println("JWT validation succeeded! " + jwtClaims);
    }
    catch (InvalidJwtException e)
    {
        // InvalidJwtException will be thrown, if the JWT failed processing or validation in anyway.
        // Hopefully with meaningful explanations(s) about what went wrong.
        System.out.println("Invalid JWT! " + e);
    }

    // In the example above we generated a key pair and used it directly for signing and verification.
    // Key exchange in the real word, however, is rarely so simple.
    // A common pattern that's emerging is for an issuer to publish its public keys
    // as a JSON Web Key Set at an HTTPS endpoint. And for the consumer of the JWT to periodically,
    // based on cache directives or known/unknown Key IDs, retrieve the keys from the host authenticated
    // and secured endpoint.

    // The HttpsJwks retrieves and caches keys from a the given HTTPS JWKS endpoint.
    // Because it retains the JWKs after fetching them, it can and should be reused
    // to improve efficiency by reducing the number of outbound calls the the endpoint.
    HttpsJwks httpsJkws = new HttpsJwks("https://example.com/jwks");

    // The HttpsJwksVerificationKeyResolver uses JWKs obtained from the HttpsJwks and will select the
    // most appropriate one to use for verification based on the Key ID and other factors provided
    // in the header of the JWS/JWT.
    HttpsJwksVerificationKeyResolver httpsJwksKeyResolver = new HttpsJwksVerificationKeyResolver(httpsJkws);


    // Use JwtConsumerBuilder to construct an appropriate JwtConsumer, which will
    // be used to validate and process the JWT. But, in this case, provide it with
    // the HttpsJwksVerificationKeyResolver instance rather than setting the
    // verification key explicitly.
    jwtConsumer = new JwtConsumerBuilder()
            // ... other set up of the JwtConsumerBuilder ...
            .setVerificationKeyResolver(httpsJwksKeyResolver)
            // ...
            .build();

    // There's also a key resolver that selects from among a given list of JWKs using the Key ID
    // and other factors provided in the header of the JWS/JWT.
    JsonWebKeySet jsonWebKeySet = new JsonWebKeySet(rsaJsonWebKey);
    JwksVerificationKeyResolver jwksResolver = new JwksVerificationKeyResolver(jsonWebKeySet.getJsonWebKeys());
    jwtConsumer = new JwtConsumerBuilder()
            // ... other set up of the JwtConsumerBuilder ...
            .setVerificationKeyResolver(jwksResolver)
            // ...
            .build();

    // Sometimes X509 certificate(s) are provided out-of-band somehow by the signer/issuer
    // and the X509VerificationKeyResolver is helpful for that situation. It will use
    // the X.509 Certificate Thumbprint Headers (x5t or x5t#S256) from the JWS/JWT to
    // select from among the provided certificates to get the public key for verification.
    X509Util x509Util = new X509Util();
    X509Certificate certificate = x509Util.fromBase64Der(
            "MIIDQjCCAiqgAwIBAgIGATz/FuLiMA0GCSqGSIb3DQEBBQUAMGIxCzAJB" +
            "gNVBAYTAlVTMQswCQYDVQQIEwJDTzEPMA0GA1UEBxMGRGVudmVyMRwwGgYD" +
            "VQQKExNQaW5nIElkZW50aXR5IENvcnAuMRcwFQYDVQQDEw5CcmlhbiBDYW1" +
            "wYmVsbDAeFw0xMzAyMjEyMzI5MTVaFw0xODA4MTQyMjI5MTVaMGIxCzAJBg" +
            "NVBAYTAlVTMQswCQYDVQQIEwJDTzEPMA0GA1UEBxMGRGVudmVyMRwwGgYDV" +
            "QQKExNQaW5nIElkZW50aXR5IENvcnAuMRcwFQYDVQQDEw5CcmlhbiBDYW1w" +
            "YmVsbDCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAL64zn8/QnH" +
            "YMeZ0LncoXaEde1fiLm1jHjmQsF/449IYALM9if6amFtPDy2yvz3YlRij66" +
            "s5gyLCyO7ANuVRJx1NbgizcAblIgjtdf/u3WG7K+IiZhtELto/A7Fck9Ws6" +
            "SQvzRvOE8uSirYbgmj6He4iO8NCyvaK0jIQRMMGQwsU1quGmFgHIXPLfnpn" +
            "fajr1rVTAwtgV5LEZ4Iel+W1GC8ugMhyr4/p1MtcIM42EA8BzE6ZQqC7VPq" +
            "PvEjZ2dbZkaBhPbiZAS3YeYBRDWm1p1OZtWamT3cEvqqPpnjL1XyW+oyVVk" +
            "aZdklLQp2Btgt9qr21m42f4wTw+Xrp6rCKNb0CAwEAATANBgkqhkiG9w0BA" +
            "QUFAAOCAQEAh8zGlfSlcI0o3rYDPBB07aXNswb4ECNIKG0CETTUxmXl9KUL" +
            "+9gGlqCz5iWLOgWsnrcKcY0vXPG9J1r9AqBNTqNgHq2G03X09266X5CpOe1" +
            "zFo+Owb1zxtp3PehFdfQJ610CDLEaS9V9Rqp17hCyybEpOGVwe8fnk+fbEL" +
            "2Bo3UPGrpsHzUoaGpDftmWssZkhpBJKVMJyf/RuP2SmmaIzmnw9JiSlYhzo" +
            "4tpzd5rFXhjRbg4zW9C+2qok+2+qDM1iJ684gPHMIY8aLWrdgQTxkumGmTq" +
            "gawR+N5MDtdPTEQ0XfIBc2cJEUyMTY5MPvACWpkA6SdS4xSvdXK3IVfOWA==");

    X509Certificate otherCertificate = x509Util.fromBase64Der(
            "MIICUDCCAbkCBETczdcwDQYJKoZIhvcNAQEFBQAwbzELMAkGA1UEBhMCVVMxCzAJ" +
            "BgNVBAgTAkNPMQ8wDQYDVQQHEwZEZW52ZXIxFTATBgNVBAoTDFBpbmdJZGVudGl0" +
            "eTEXMBUGA1UECxMOQnJpYW4gQ2FtcGJlbGwxEjAQBgNVBAMTCWxvY2FsaG9zdDAe" +
            "Fw0wNjA4MTExODM1MDNaFw0zMzEyMjcxODM1MDNaMG8xCzAJBgNVBAYTAlVTMQsw" +
            "CQYDVQQIEwJDTzEPMA0GA1UEBxMGRGVudmVyMRUwEwYDVQQKEwxQaW5nSWRlbnRp" +
            "dHkxFzAVBgNVBAsTDkJyaWFuIENhbXBiZWxsMRIwEAYDVQQDEwlsb2NhbGhvc3Qw" +
            "gZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBAJLrpeiY/Ai2gGFxNY8Tm/QSO8qg" +
            "POGKDMAT08QMyHRlxW8fpezfBTAtKcEsztPzwYTLWmf6opfJT+5N6cJKacxWchn/" +
            "dRrzV2BoNuz1uo7wlpRqwcaOoi6yHuopNuNO1ms1vmlv3POq5qzMe6c1LRGADyZh" +
            "i0KejDX6+jVaDiUTAgMBAAEwDQYJKoZIhvcNAQEFBQADgYEAMojbPEYJiIWgQzZc" +
            "QJCQeodtKSJl5+lA8MWBBFFyZmvZ6jUYglIQdLlc8Pu6JF2j/hZEeTI87z/DOT6U" +
            "uqZA83gZcy6re4wMnZvY2kWX9CsVWDCaZhnyhjBNYfhcOf0ZychoKShaEpTQ5UAG" +
            "wvYYcbqIWC04GAZYVsZxlPl9hoA=");

    X509VerificationKeyResolver x509VerificationKeyResolver = new X509VerificationKeyResolver(certificate, otherCertificate);

    // Optionally the X509VerificationKeyResolver can attempt to verify the signature
    // with the key from each of the provided certificates, if no X.509 Certificate
    // Thumbprint Header is present in the JWT/JWS.
    x509VerificationKeyResolver.setTryAllOnNoThumbHeader(true);

    jwtConsumer = new JwtConsumerBuilder()
            // ... other set up of the JwtConsumerBuilder ...
            .setVerificationKeyResolver(x509VerificationKeyResolver)
            // ...
            .build();


    // Note that on the producing side, the X.509 Certificate Thumbprint Header
    // can be set like this on the JWS (which is the JWT)
    jws.setX509CertSha1ThumbprintHeaderValue(certificate);

    // In some cases you won't have enough information to set up your JWT consumer without cracking open
    // the JWT first. For example, in some contexts you might not know who issued the token without looking
    // at the "iss" claim inside the JWT.
    // This can be done efficiently and relatively easily using two JwtConsumers in a "two-pass" validation
    // of sorts - the first JwtConsumer parses the JWT and the second one does the actual validation.

    // Build a JwtConsumer that doesn't check signatures or do any validation.
    JwtConsumer firstPassJwtConsumer = new JwtConsumerBuilder()
            .setSkipAllValidators()
            .setDisableRequireSignature()
            .setSkipSignatureVerification()
            .build();

    //The first JwtConsumer is basically just used to parse the JWT into a JwtContext object.
    JwtContext jwtContext = firstPassJwtConsumer.process(jwt);

    // From the JwtContext we can get the issuer, or whatever else we might need,
    // to lookup or figure out the kind of validation policy to apply
    String issuer = jwtContext.getJwtClaims().getIssuer();

    // Just using the same key here but you might, for example, have a JWKS URIs configured for
    // each issuer, which you'd use to set up a HttpsJwksVerificationKeyResolver
    Key verificationKey = rsaJsonWebKey.getKey();

    // Using info from the JwtContext, this JwtConsumer is set up to verify
    // the signature and validate the claims.
    JwtConsumer secondPassJwtConsumer = new JwtConsumerBuilder()
            .setExpectedIssuer(issuer)
            .setVerificationKey(verificationKey)
            .setRequireExpirationTime()
            .setAllowedClockSkewInSeconds(30)
            .setRequireSubject()
            .setExpectedAudience("Audience")
            .build();

    // Finally using the second JwtConsumer to actually validate the JWT. This operates on
    // the JwtContext from the first processing pass, which avoids redundant parsing/processing.
    secondPassJwtConsumer.processContext(jwtContext);

    // Generate an EC key pair, which will be used for signing and verification of the JWT, wrapped in a JWK
    EllipticCurveJsonWebKey senderJwk = EcJwkGenerator.generateJwk(EllipticCurves.P256);

    // Give the JWK a Key ID (kid), which is just the polite thing to do
    senderJwk.setKeyId("sender's key");


    // Generate an EC key pair, wrapped in a JWK, which will be used for encryption and decryption of the JWT
    EllipticCurveJsonWebKey receiverJwk = EcJwkGenerator.generateJwk(EllipticCurves.P256);

    // Give the JWK a Key ID (kid), which is just the polite thing to do
    receiverJwk.setKeyId("receiver's key");

    // Create the Claims, which will be the content of the JWT
    JwtClaims claims = new JwtClaims();
    claims.setIssuer("sender");  // who creates the token and signs it
    claims.setAudience("receiver"); // to whom the token is intended to be sent
    claims.setExpirationTimeMinutesInTheFuture(10); // time when the token will expire (10 minutes from now)
    claims.setGeneratedJwtId(); // a unique identifier for the token
    claims.setIssuedAtToNow();  // when the token was issued/created (now)
    claims.setNotBeforeMinutesInThePast(2); // time before which the token is not yet valid (2 minutes ago)
    claims.setSubject("subject"); // the subject/principal is whom the token is about
    claims.setClaim("email","mail@example.com"); // additional claims/attributes about the subject can be added
    List<String> groups = Arrays.asList("group-1", "other-group", "group-3");
    claims.setStringListClaim("groups", groups); // multi-valued claims work too and will end up as a JSON array

    // A JWT is a JWS and/or a JWE with JSON claims as the payload.
    // In this example it is a JWS nested inside a JWE
    // So we first create a JsonWebSignature object.
    JsonWebSignature jws = new JsonWebSignature();

    // The payload of the JWS is JSON content of the JWT Claims
    jws.setPayload(claims.toJson());

    // The JWT is signed using the sender's private key
    jws.setKey(senderJwk.getPrivateKey());

    // Set the Key ID (kid) header because it's just the polite thing to do.
    // We only have one signing key in this example but a using a Key ID helps
    // facilitate a smooth key rollover process
    jws.setKeyIdHeaderValue(senderJwk.getKeyId());

    // Set the signature algorithm on the JWT/JWS that will integrity protect the claims
    jws.setAlgorithmHeaderValue(AlgorithmIdentifiers.ECDSA_USING_P256_CURVE_AND_SHA256);

    // Sign the JWS and produce the compact serialization, which will be the inner JWT/JWS
    // representation, which is a string consisting of three dot ('.') separated
    // base64url-encoded parts in the form Header.Payload.Signature
    String innerJwt = jws.getCompactSerialization();

    // The outer JWT is a JWE
    JsonWebEncryption jwe = new JsonWebEncryption();

    // The output of the ECDH-ES key agreement will encrypt a randomly generated content encryption key
    jwe.setAlgorithmHeaderValue(KeyManagementAlgorithmIdentifiers.ECDH_ES_A128KW);

    // The content encryption key is used to encrypt the payload
    // with a composite AES-CBC / HMAC SHA2 encryption algorithm
    String encAlg = ContentEncryptionAlgorithmIdentifiers.AES_128_CBC_HMAC_SHA_256;
    jwe.setEncryptionMethodHeaderParameter(encAlg);

    // We encrypt to the receiver using their public key
    jwe.setKey(receiverJwk.getPublicKey());
    jwe.setKeyIdHeaderValue(receiverJwk.getKeyId());

    // A nested JWT requires that the cty (Content Type) header be set to "JWT" in the outer JWT
    jwe.setContentTypeHeaderValue("JWT");

    // The inner JWT is the payload of the outer JWT
    jwe.setPayload(innerJwt);

    // Produce the JWE compact serialization, which is the complete JWT/JWE representation,
    // which is a string consisting of five dot ('.') separated
    // base64url-encoded parts in the form Header.EncryptedKey.IV.Ciphertext.AuthenticationTag
    String jwt = jwe.getCompactSerialization();


    // Now you can do something with the JWT. Like send it to some other party
    // over the clouds and through the interwebs.
    System.out.println("JWT: " + jwt);


    // Use JwtConsumerBuilder to construct an appropriate JwtConsumer, which will
    // be used to validate and process the JWT.
    // The specific validation requirements for a JWT are context dependent, however,
    // it typically advisable to require a expiration time, a trusted issuer, and
    // and audience that identifies your system as the intended recipient.
    JwtConsumer jwtConsumer = new JwtConsumerBuilder()
            .setRequireExpirationTime() // the JWT must have an expiration time
            .setRequireSubject() // the JWT must have a subject claim
            .setExpectedIssuer("sender") // whom the JWT needs to have been issued by
            .setExpectedAudience("receiver") // to whom the JWT is intended for
            .setDecryptionKey(receiverJwk.getPrivateKey()) // decrypt with the receiver's private key
            .setVerificationKey(senderJwk.getPublicKey()) // verify the signature with the sender's public key
            .build(); // create the JwtConsumer instance

    try
    {
        //  Validate the JWT and process it to the Claims
        JwtClaims jwtClaims = jwtConsumer.processToClaims(jwt);
        System.out.println("JWT validation succeeded! " + jwtClaims);
    }
    catch (InvalidJwtException e)
    {
        // InvalidJwtException will be thrown, if the JWT failed processing or validation in anyway.
        // Hopefully with meaningful explanations(s) about what went wrong.
        System.out.println("Invalid JWT! " + e);
    }