title: How to get oauth2 access token in a spring boot application (not a web application) using spring security 5
body: <p>I need to get access token (grant_type = client_credentials) in the service layer of my spring boot application to talk to other microservice (service to service interaction). There is no spring http session or auth at this layer, I just have client_id, client_secret and token url. These properties are set in application.properties as:</p>
  
  <pre><code>spring.security.oauth2.client.registration.auth1.client-id=***
  spring.security.oauth2.client.registration.auth1.client-secret=***
  spring.security.oauth2.client.registration.auth1.authorization-grant-type=client_credentials
  spring.security.oauth2.client.provider.auth1.tokenUri=***
  </code></pre>
  
  <p>This seemed simple with Spring Security OAuth, but can't figure out with Spring security. Referred the documents for spring security 5, but everything seems to be in context of web interface. I understand I could just make http call to get the token with the info I have, but I wanted to utilize the framework...</p>
  
  <p>Scenario:
  Lets call this spring boot app service A. There are other services which might call A to process updates on http or send kafka message on a topic which A listens to. When A processes the update/message, it needs to send some data to service B which requires access token for authz. This is where I need the access token. So the interaction is essentially service-service and is not specific to user.</p>