public ValidationServiceClient(String backendServerURL, String username, String password) throws Exception{
String serviceURL = backendServerURL + "OAuth2TokenValidationService";
try {
stub = new OAuth2TokenValidationServiceStub(serviceURL);
CarbonUtils.setBasicAccessSecurityHeaders(username, password, true, stub._getServiceClient());
} catch (AxisFault e) {
log.error("Error initializing OAuth2 Client");
throw new Exception("Error initializing OAuth Client", e);
}