spring-cloud-security/src/main/java/org/springframework/cloud/security/oauth2/client/feign/OAuth2FeignRequestInterceptor.java
protected String extract(String tokenType) {
		OAuth2AccessToken accessToken = getToken();
		return String.format("%s %s", tokenType, accessToken.getValue());
	}
protected String extract(String tokenType) {
		OAuth2AccessToken accessToken = getToken();
		return String.format("%s %s", tokenType, accessToken.getValue());
	}
Extracts the token extract id the access token exists or returning an empty extract
if there is no one on the context it may occasionally causes Unauthorized response
since the token extract is empty.
@param tokenType type name of token
@return token value from context if it exists otherwise empty String