Sample Code Google Login Oauth2 Java Api

google-service.java

// Required for Http Request and json management for credentials
HttpTransport httpTransport = new NetHttpTransport();
JacksonFactory jsonFactory = new JacksonFactory();

// Go to the Google API Console, open your application's
// credentials page, and copy the client ID and client secret.
// Then paste them into the following code.
String clientId = "YOUR_CLIENT_ID";
String clientSecret = "YOUR_CLIENT_SECRET";

// Or your redirect URL for web based applications.
String redirectUrl = "urn:ietf:wg:oauth:2.0:oob";

//  Default scope is profile, but you can add email and openid for more permissions
String scope = "profile email openid";

// Step 1: Create Authorize Url for auhorizing the user -->
String authorizationUrl = new GoogleBrowserClientRequestUrl(clientId, redirectUrl, Arrays.asList(scope))
       .build();

// Point or redirect your user to the authorizationUrl where he will get access code

//Sample code you will get from url
code=4%2FSQEGs6ivqKz2YYpdwzgkLRHyr4nq2-hxHUy336-80TgnmJyyQTzjWnly3x5QwDndN3kFNyCMHTaIFGBWauOOoGA
// here code is parameter you need to get from URL
// End of Step 1 <--

// Step 2.
// Authorization code we get after url authentication need to be decoded
String decodedAuthorizationCode = URLDecoder.decode(authorizationCode,"UTF-8");
        
// Create exchange request for Google access Token
GoogleTokenResponse googleTokenResponse = new GoogleAuthorizationCodeTokenRequest(
            httpTransport,JSON_FACTORY, "https://www.googleapis.com/oauth2/v4/token",
            this.clientId,this.clientSecret, decodedAuthorizationCode, REDIRECT_URI)
            .execute();

// Extract token from token response
String accessTokenFromGoogle = googleTokenResponse.getAccessToken();

// Extract Id Token from response
GoogleIdToken googleIdToken = googleTokenResponse.parseIdToken();

//Step 2  End--> 


//Step 3. Get User data from either Payload from token response object (openid scope is required)

// Get payload from id token containing user data 
GoogleIdToken.Payload payload = googleIdToken.getPayload();

String userId = payload.getSubject();  // Use this value as a key to identify a user.
String email = payload.getEmail();
boolean emailVerified = Boolean.valueOf(payload.getEmailVerified());
String name = (String) payload.get("name");
String pictureUrl = (String) payload.get("picture");
String locale = (String) payload.get("locale");
String familyName = (String) payload.get("family_name");
String givenName = (String) payload.get("given_name");
// Step 3 End


// Step 4 Get User Info from OAuth2 by access token from previous step no. 2 

// Create new google credentials with access token from googl
GoogleCredential googleCredential = new GoogleCredential().setAccessToken(accessTokenFromGoogle);

// Create Oauth Object with token credential
Oauth2 oauth2 = new Oauth2.Builder(
       httpTransport,jsonFactory,googleCredential)
       .setHttpRequestInitializer(googleCredential)
       .setApplicationName("Dehaze") // Change to name of your app
       .build();

// Create UserInfo Plus object;
String id = useririnfoplus.getId();
String email = userinfoplus.getEmail();  
String name = useririnfoplus.getName();  // Balvinder Singh
String familyName = userinfoplus.getFamilyName();  // Singh
String givenName = userinfoplus.getGivenName();   // Balvinder
String locale = userinfoplus.getLocale();   // en
Boolean emailVerified = userinfoplus.getVerifiedEmail();  // true in case of verified email
String profilePicUrl = userinfoplus.getPicture();  // url of profile pic