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For this recipe, we did not configure the base URL, which must be done to avoid issues when running your application behind a proxy. To do so, you might add the following bean declaration inside GoogleConfigurerAdapter:

@Bean 
public ConnectController connectController( 
      ConnectionFactoryLocator locator, 
      ConnectionRepository repository) { 
 
      ConnectController controller =  
            new ConnectController(locator, repository); 
      controller.setApplicationUrl("http://localhost:8080"); 
      return controller; 
} 

Do not forget to define the same redirect URL for the OAuth 2.0 Provider and to make all the communications through TLS/SSL.

To improve security configurations, you might use a database to store all users and respective credentials being held in a cryptographically manner (these features are provided by Spring Security and can be read about in the official documents at https://projects.spring.io/spring-security/).