oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/OAuth2ClientCredentialsGrantRequestEntityConverter.java
private MultiValueMap<String, String> buildFormParameters(OAuth2ClientCredentialsGrantRequest clientCredentialsGrantRequest) {
		ClientRegistration clientRegistration = clientCredentialsGrantRequest.getClientRegistration();

		MultiValueMap<String, String> formParameters = new LinkedMultiValueMap<>();
		formParameters.add(OAuth2ParameterNames.GRANT_TYPE, clientCredentialsGrantRequest.getGrantType().getValue());
		if (!CollectionUtils.isEmpty(clientRegistration.getScopes())) {
			formParameters.add(OAuth2ParameterNames.SCOPE,
					StringUtils.collectionToDelimitedString(clientRegistration.getScopes(), " "));
		}
		if (ClientAuthenticationMethod.POST.equals(clientRegistration.getClientAuthenticationMethod())) {
			formParameters.add(OAuth2ParameterNames.CLIENT_ID, clientRegistration.getClientId());
			formParameters.add(OAuth2ParameterNames.CLIENT_SECRET, clientRegistration.getClientSecret());
		}

		return formParameters;
	}
private MultiValueMap<String, String> buildFormParameters(OAuth2ClientCredentialsGrantRequest clientCredentialsGrantRequest) {
		ClientRegistration clientRegistration = clientCredentialsGrantRequest.getClientRegistration();

		MultiValueMap<String, String> formParameters = new LinkedMultiValueMap<>();
		formParameters.add(OAuth2ParameterNames.GRANT_TYPE, clientCredentialsGrantRequest.getGrantType().getValue());
		if (!CollectionUtils.isEmpty(clientRegistration.getScopes())) {
			formParameters.add(OAuth2ParameterNames.SCOPE,
					StringUtils.collectionToDelimitedString(clientRegistration.getScopes(), " "));
		}
		if (ClientAuthenticationMethod.POST.equals(clientRegistration.getClientAuthenticationMethod())) {
			formParameters.add(OAuth2ParameterNames.CLIENT_ID, clientRegistration.getClientId());
			formParameters.add(OAuth2ParameterNames.CLIENT_SECRET, clientRegistration.getClientSecret());
		}

		return formParameters;
	}
Returns a {@link MultiValueMap} of the form parameters used for the Access Token Request body.

@param clientCredentialsGrantRequest the client credentials grant request
@return a {@link MultiValueMap} of the form parameters used for the Access Token Request body