@Override
        public Map<String, String> getHeaders() {
            String tokenValue = getTokenValue();
            if (StringUtils.isNullOrEmpty(tokenValue) ) {
                return new HashMap<String, String>();
            }
            return Collections.singletonMap("Authorization", tokenValue);
        }
A URI resolver that uses environment variable {@value CONTAINER_CREDENTIALS_FULL_URI} as the URI
for the metadata service.
Optionally an authorization token can be provided using the {@value CONTAINER_AUTHORIZATION_TOKEN} environment variable.
aws-java-sdk-core/src/main/java/com/amazonaws/auth/ContainerCredentialsProvider.java