Creating an OAuth2 Application in Google

To begin, we need to set up an OAuth application within the Google Cloud Platform console. Follow these steps:

1. In the top-left corner, near the Google Cloud logo, click the dropdown menu and select the "NEW PROJECT" button. Name your project "simple-web-chat" and click "CREATE."
2. Ensure your project is selected in the dropdown, then navigate to the burger menu on the top-left, select "APIs & Services," and choose "OAuth consent screen."
3. On the consent screen, select "External" and click the "Create" button.
4. In the "App information" section, enter "Simple Web Chat" as the app name and provide your email for user support and developer contact. Click "SAVE AND CONTINUE."
5. Under "Scopes," click "ADD AND REMOVE SCOPES," select "profile" and "openid," then click "UPDATE" and "SAVE AND CONTINUE."
6. In the "Test users" section, add your email as a test user and save the changes.
7. Finally, review the OAuth consent summary and click "BACK TO DASHBOARD."

Next, we need to create credentials:

1. Go to the "Credentials" menu and click "+ CREATE CREDENTIALS," then select "OAuth client ID."
2. Choose "Web application" for the application type and name it "Simple Web Chat App." Add the redirect URI: http://localhost:8080/login/oauth2/code/google.
3. Click "CREATE." The Client ID and Client Secret will be displayed; make sure to note them down as they will be used for login testing.

Creating the GoogleOAuth2UserInfoExtractor Class

Next, let's create the GoogleOAuth2UserInfoExtractor class in the security package. This class will handle user information extraction:

package com.example.simplewebchat.security;

import org.springframework.security.core.authority.SimpleGrantedAuthority;

import org.springframework.security.oauth2.client.userinfo.OAuth2UserRequest;

import org.springframework.security.oauth2.core.user.OAuth2User;

import org.springframework.stereotype.Service;

import java.util.Collections;

@Service

public class GoogleOAuth2UserInfoExtractor implements OAuth2UserInfoExtractor {

@Override

public CustomUserDetails extractUserInfo(OAuth2User oAuth2User) {

CustomUserDetails customUserDetails = new CustomUserDetails();

customUserDetails.setUsername(retrieveAttr("given_name", oAuth2User) + retrieveAttr("family_name", oAuth2User));

customUserDetails.setName(retrieveAttr("name", oAuth2User));

customUserDetails.setAttributes(oAuth2User.getAttributes());

customUserDetails.setAuthorities(Collections.singletonList(new SimpleGrantedAuthority(WebSecurityConfig.CHAT_USER)));

return customUserDetails;

}

@Override

public boolean accepts(OAuth2UserRequest userRequest) {

return "google".equalsIgnoreCase(userRequest.getClientRegistration().getRegistrationId());

}

}

The GoogleOAuth2UserInfoExtractor class is designed to extract user details from Google's OAuth2 provider. It implements the OAuth2UserInfoExtractor interface, providing methods to retrieve user information and verify the OAuth2 provider.

Updating application.properties

Add the following lines to your application.properties file:

spring.security.oauth2.client.registration.google.clientId=${GOOGLE_CLIENT_ID}

spring.security.oauth2.client.registration.google.clientSecret=${GOOGLE_CLIENT_SECRET}

spring.security.oauth2.client.registration.google.scope=profile

These lines configure the OAuth2 client registration for Google, ensuring that the Client ID and Client Secret are pulled from environment variables rather than being hard-coded. The scope is set to "profile," requesting access to basic user profile data.

Modifying login.html

In the login.html file, implement the following changes:

<a th:href="@{/oauth2/authorization/google}">Google</a>

This line establishes the link for initiating the OAuth2 authorization flow with Google.