Authorize Method for apple sign in

apple-authorize.java

/*************** Imports  ***************/
import okhttp3.FormBody;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;
import org.json.JSONObject;
import org.springframework.cloud.cloudfoundry.com.fasterxml.jackson.databind.ObjectMapper;

private static String APPLE_AUTH_URL = "https://appleid.apple.com/auth/token";

/** Social Paramters DTO check here
https://gist.github.com/balvinder294/8a6c8c4754c309a3a7052ed037bc3c3b

Apple Id token payload DTO here
https://gist.github.com/balvinder294/72a437791aab7c9708b5a74dcece41b9

Token Response DTO here
https://gist.github.com/balvinder294/344284456e06c37d5afcdf08b8381092
*****************/
/****************************************/
    public void authorizeApple(SocialParametersDTO socialParametersDTO) throws Exception {
        log.debug("Get Apple User Profile {}", socialParametersDTO);
        String appClientId = null;
        if (socialParametersDTO.getIdentifierFromApp() != null) {
          // if kid is sent from mobile app
            appClientId = socialParametersDTO.getIdentifierFromApp();
        } else {
          // if doing sign in with web using predefined identifier
            appClientId = appleClientId;
        }
        SocialUserDTO socialUserDTO = new SocialUserDTO();
        // generate personal verification token
        String token = generateJWT(appClientId);
        
        ////////// Get OAuth Token from Apple by exchanging code
        // Prepare client, you can use other Rest client library also
        OkHttpClient okHttpClient = new OkHttpClient()
            .newBuilder()
            .connectTimeout(70, TimeUnit.SECONDS)      
            .writeTimeout(70, TimeUnit.SECONDS)
            .readTimeout(70, TimeUnit.SECONDS)
            .build();
       // Request body for sending parameters as FormUrl Encoded
        RequestBody requestBody = new FormBody
            .Builder()
            .add("client_id", appClientId)
            .add("client_secret", token)
            .add("grant_type", "authorization_code")
            .add("code", socialParametersDTO.getAuthorizationCode())
            .build();

       // Prepare rest request
        Request request = new Request
          .Builder()
          .url(APPLE_AUTH_URL)
          .post(requestBody)
          .header("Content-Type", "application/x-www-form-urlencoded")
          .build();

        // Execute api call and get Response
        Response resp = okHttpClient.newCall(request).execute();
        String response = resp.body().string();
        // Parse response as DTO
        ObjectMapper objectMapper = new ObjectMapper();
        TokenResponse tokenResponse = objectMapper.readValue(response, TokenResponse.class);
        // Parse id token from Token
        String idToken = tokenResponse.getId_token();
        String payload = idToken.split("\\.")[1];// 0 is header we ignore it for now
        String decoded = new String(Decoders.BASE64.decode(payload));
        AppleIDTokenPayload idTokenPayload = new Gson().fromJson(decoded, AppleIDTokenPayload.class);
    
        // if we have user obj also from Web or mobile
        // we get only at 1st authorization
        if (socialParametersDTO.getUserObj() != null ) {
            JSONObject user = new JSONObject(userObj);
            JSONObject name = user.has("name") ? user.getJSONObject("name") : null;
            String firstName = name.getString("firstName);
            String lastName = name.getString("lastName);
        }

        // Add your logic here
    }

Hi Balvinder.
There is one question: where did you get userObj object ? Because there is no initialization. (See line 76)
Thanks in advance.