OAuth2RestTemplate - Client Side Caching

Question

I see the below restTemplate being used for fetching OAuth token. I don't see any explicit call to cache the token in my application. However I see the same token value being returned by this template. Does OAuth2RestTemplate inherently implement client side caching? If so , does it make an explicit call to the OAuth2 endpoint when the token expires?

@Qualifier("oauth")
@Bean
public OAuth2RestTemplate restTemplate(@Qualifier("resourceDetails") ClientCredentialsResourceDetails resourceDetails) {
    return new OAuth2RestTemplate(resourceDetails);
}

I saw the below in the documentation -

getAccessToken public OAuth2AccessToken getAccessToken() throws UserRedirectRequiredException

Acquire or renew an access token for the current context if necessary. This method will be called automatically when a request is executed (and the result is cached), but can also be called as a standalone method to pre-populate the token.

Answer 1

it's clearly said that the token is cached in the context (DefaultOAuth2ClientContext object) created when defining a resource. however, the token is managed by calling getAccessToken(). here is what the Docs says about getAccessToken():

Acquire or renew an access token for the current context if necessary. This method will be called automatically * when a request is executed (and the result is cached), but can also be called as a standalone method to * pre-populate the token.

the token is cached until it's Expired, then it will be renewed automatically. this snippet of code from getAccessToken() describes it:

if (accessToken == null || accessToken.isExpired()) {
            try {
                accessToken = acquireAccessToken(context);
            }

About Caching mechanism, By default spring provides an in-memory caching

DefaultOAuth2ClientContext

but you can provide your own implementation of

OAuth2ClientContext