diff --git a/README.md b/README.md
index f4fafcd..9c4b532 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ Next, you have to configure your web page for Sign in with Apple. Follow the gui
 # Example
 ## Using `AppleAuthProvider.java` `AppleClientPrivateKeyFactory.java`
 First order of business should be creating an instance of `ECPrivateKey` representing the client's(your) private key.<br/>
-`AppleKeyProvider` can help you create a `ECPrivateKey` if you have your private key as string or stream (from a p8 for example).
+`AppleClientPrivateKeyFactory` can help you create a `ECPrivateKey` if you have your private key as string or stream (from a p8 for example).
 
 Creating a new instance of `AppleAuthProvider`, should be trivial at this point. The only two parameters that are not 
 self explanatory are the `SecretGenerator` and the collection of scopes.<br/>
@@ -30,10 +30,10 @@ Once you have your `AppleAuthProvider` instance you can:
 ## Handling initial response from Apple
 After the user clicks on the "Sign in with Apple" button on your page they will be redirected to https://appleid.apple.com/. 
 After they provide their credentials Apple will make a POST request to the url that you have specified as Redirect URL. 
-It will contain a ```code``` field. Its contents is what should be handed down to `makeNewAuthorisationTokenRequest` in order retrieve thee authorization token (it will also contain the state used to create the redirect url).
+It will contain a `code` field. Its contents is what should be handed down to `makeNewAuthorisationTokenRequest` in order retrieve the authorization token (it will also contain the state used to create the redirect url).
 Keep in mind that tokens returned from Apple are short-lived, so you should create a session or a user in your system 
-using the returned ```AppleAuthorizationToken``` object. After that you can verify if the user is 
-still logged in using "Sign in with Apple" by retrieving a refresh token using the ```makeNewRefreshTokenRequest``` method.
+using the returned `AppleAuthorizationToken` object. After that you can verify if the user is 
+still logged in using "Sign in with Apple" by retrieving a refresh token using the `makeNewRefreshTokenRequest` method.
 
 ```java
         public class AppleIdTokenManager {
@@ -44,14 +44,14 @@ still logged in using "Sign in with Apple" by retrieving a refresh token using t
             private static final String REDIRECT_URL = "Your redirect url";
         
             public static void main(String[] args) throws IOException, InvalidKeySpecException {
-                //Generating your private key.
-                //This could be just a string containing the key.
+                // Generating your private key.
+                // This could be just a string containing the key.
                 InputStream pkStream = AppleIdTokenManager.class
                         .getClassLoader().getResourceAsStream("your_pk_file.p8");
                 AppleClientPrivateKeyFactory appleClientPrivateKeyFactory = new AppleClientPrivateKeyFactory();
                 ECPrivateKey privateKey = appleClientPrivateKeyFactory.getEcPrivateKey(pkStream);
                 
-                //Creating provider instance.
+                // Creating provider instance.
                 SecretGenerator secretGenerator = new SecretGenerator();
                 AppleAuthProvider appleAuthProvider = new AppleAuthProvider(
                         CLIENT_ID,
@@ -63,20 +63,20 @@ still logged in using "Sign in with Apple" by retrieving a refresh token using t
                         REDIRECT_URL
                 );
                 
-                //We are ready to start using the provider.
+                // We are ready to start using the provider.
 
-                //Generate a url and navigate the user to it.
+                // Generate a url and navigate the user to it.
                 String loginLink = appleAuthProvider.getLoginLink("Some form of state");
                 
-                //Once the user is redirected back to our domain get the "code" in the request.
+                // Once the user is redirected back to our domain get the "code" in the request.
                 String authCode = "the code in the callback request";
-                //Now we can authenticate the user.
+                // Now we can authenticate the user.
                 AppleAuthorizationToken initialToken = appleAuthProvider.makeNewAuthorisationTokenRequest(authCode);
-                //After the authentication we should check (not more than once every once 24 hours) if the user still 
-                // logged in using "Sign in with Apple" by retrieving a refresh token.
+                // After the authentication we should check (not more than once every 24h) if the user 
+                // is still logged in using "Sign in with Apple" by retrieving a refresh token.
                 AppleAuthorizationToken refreshToken = appleAuthProvider.makeNewRefreshTokenRequest(initialToken
                         .getRefreshToken());
         
             }
         }
-```
\ No newline at end of file
+```
diff --git a/pom.xml b/pom.xml
index 9e4a786..a31aa6d 100644
--- a/pom.xml
+++ b/pom.xml
@@ -84,21 +84,20 @@
         <dependency>
             <groupId>com.auth0</groupId>
             <artifactId>java-jwt</artifactId>
-            <version>3.10.3</version>
+            <version>4.0.0</version>
         </dependency>
 
         <dependency>
             <groupId>com.auth0</groupId>
             <artifactId>jwks-rsa</artifactId>
-            <version>0.11.0</version>
+            <version>0.21.1</version>
         </dependency>
 
         <dependency>
             <groupId>com.google.api-client</groupId>
             <artifactId>google-api-client</artifactId>
-            <version>1.30.9</version>
+            <version>2.0.0</version>
         </dependency>
     </dependencies>
 
-
-</project>
\ No newline at end of file
+</project>
diff --git a/src/main/java/com/accedia/apple/auth/AppleAuthProvider.java b/src/main/java/com/accedia/apple/auth/AppleAuthProvider.java
index a8a4f2a..fd904c6 100644
--- a/src/main/java/com/accedia/apple/auth/AppleAuthProvider.java
+++ b/src/main/java/com/accedia/apple/auth/AppleAuthProvider.java
@@ -12,7 +12,7 @@
 import com.google.api.client.http.HttpTransport;
 import com.google.api.client.http.javanet.NetHttpTransport;
 import com.google.api.client.json.JsonFactory;
-import com.google.api.client.json.jackson2.JacksonFactory;
+import com.google.api.client.json.gson.GsonFactory;
 import com.google.common.base.Supplier;
 import com.google.common.base.Suppliers;
 import com.google.common.collect.ImmutableList;
@@ -26,7 +26,8 @@
 import java.util.List;
 import java.util.Optional;
 import java.util.concurrent.TimeUnit;
-import java.util.stream.Collectors;
+
+import static java.util.stream.Collectors.toList;
 
 public class AppleAuthProvider {
 
@@ -45,7 +46,7 @@ public class AppleAuthProvider {
     private final long secretLifeInSec;
     private final GenericUrl appleAuthTokenUrl;
     private final String appleAuthAuthorizationUrl;
-    private UserDataDeserializer userDataDeserializer;
+    private final UserDataDeserializer userDataDeserializer;
     private final List<String> appleUserScopes;
     private final String redirectUrl;
     private final HttpTransport httpTransport;
@@ -81,11 +82,11 @@ public AppleAuthProvider(String clientId, String keyId, String teamId, SecretGen
                 DEFAULT_APPLE_AUTH_AUTHORIZE_URL,
                 new UserDataDeserializer(),
                 new NetHttpTransport(),
-                new JacksonFactory(),
+                new GsonFactory(),
                 DEFAULT_MAX_TIMEOUT_IN_SEC,
                 secretGenerator,
                 privateKey,
-                () -> Instant.now(),
+                Instant::now,
                 DEFAULT_SECRET_LIFE_IN_SEC,
                 new AppleKeyProvider(),
                 scopes,
@@ -146,7 +147,7 @@ public AppleAuthProvider(String clientId,
         this.secretLifeInSec = secretLifeInSec;
         this.userDataDeserializer = userDataDeserializer;
         this.appleUserScopes = scopes != null ? ImmutableList.copyOf(
-                scopes.stream().map(AppleUserScope::getLiteral).collect(Collectors.toList())
+                scopes.stream().map(AppleUserScope::getLiteral).collect(toList())
         ) : null;
         this.appleAuthTokenUrl = new GenericUrl(appleAuthTokenUrl);
         this.jsonFactory = jsonFactory;
@@ -159,7 +160,7 @@ public AppleAuthProvider(String clientId,
         this.httpTransport = httpTransport;
 
         Algorithm validationAlg = Algorithm.RSA256(appleKeyProvider);
-        this.jwtVerifier =  JWT.require(validationAlg)
+        this.jwtVerifier = JWT.require(validationAlg)
                 .build();
 
     }
@@ -182,13 +183,13 @@ public String getLoginLink(String state) {
                 .setResponseTypes(Arrays.asList("code", "id_token"))
                 .setScopes(appleUserScopes)
                 .setState(state)
-                .set("response_mode", "form_post")//Could be parameterized based on scope.
+                .set("response_mode", "form_post")  //Could be parameterized based on scope.
                 .build();
     }
 
     /**
-     * Makes an authorisation request. Retrieves an User's date from Apple. Use this object to create users or sessions.
-     * @param authCode Received from Apple after successfully redirecting the use.
+     * Makes an authorisation request. Retrieves a User's date from Apple. Use this object to create users or sessions.
+     * @param authCode Received from Apple after successfully redirecting the user.
      * @throws IOException
      */
     public AppleAuthorizationToken makeNewAuthorisationTokenRequest(String authCode) throws IOException {
@@ -201,7 +202,7 @@ public AppleAuthorizationToken makeNewAuthorisationTokenRequest(String authCode)
     /**
      * Verifies if a token is valid.
      * Use this method to check daily if the user is still signed in on your app using Apple ID.
-     * @param refreshToken 
+     * @param refreshToken
      * @return
      * @throws IOException
      */
@@ -218,13 +219,13 @@ private AppleAuthorizationToken executeTokenRequest(TokenRequest tokenRequest) t
         TokenResponse tokenResponse = tokenRequest.execute();
         Optional<String> idToken = Optional.ofNullable(tokenResponse.get("id_token")).map(Object::toString);
         idToken.ifPresent(this::validateToken);
-        Optional<UserData> userData = idToken.map(userDataDeserializer::getUserDataFromIdToken);
+        UserData userData = idToken.map(userDataDeserializer::getUserDataFromIdToken).orElse(null);
         return new AppleAuthorizationToken(
                 tokenResponse.getAccessToken(),
                 tokenResponse.getExpiresInSeconds(),
                 idToken.orElse(null),
                 tokenResponse.getRefreshToken(),
-                userData.orElse(null));
+                userData);
     }
 
     private void validateToken(String token) {