updated VRE Confirm URL

src/main/java/org/gcube/portal/ddas/DdasVREService.java

@@ -28,8 +28,7 @@ public class DdasVREService extends HttpServlet {
 	private static final long serialVersionUID = 1L;
 	private static com.liferay.portal.kernel.log.Log _log = LogFactoryUtil.getLog(DdasVREService.class);  
 	private static final int CACHE_SECONDS_EXPIRATION = 1800; //30 minutes
-
-
+	private static final String VRE_CONFIRM_URL = "https://blue-cloud.d4science.org/group/bluecloud-gateway/vre-data-pool";
 	/**
 	 * @see HttpServlet#HttpServlet()
 	 */
@@ -85,7 +84,8 @@ public class DdasVREService extends HttpServlet {
 			Base64.Encoder withoutPaddingEncoder = Base64.getEncoder().withoutPadding();
 			String requestIdParam  =  withoutPaddingEncoder.encodeToString("otp".getBytes());
 			String message = "Started downloading order files to Virtual Research Environment '"+requestId+"'";
-			String vreConfirmUrl = "https://blue-cloud.d4science.org/group/bluecloud-gateway/vre-data-pool?"+requestIdParam+"="+otp; //redirect URL
+			
+			String vreConfirmUrl = new StringBuilder(VRE_CONFIRM_URL).append("?").append(requestIdParam).append("=").append(otp).toString(); //redirect URL
 			URL theURL = new URL(vreConfirmUrl);
 			theResponse = new BrokerResponse(status, message, theURL);
 		}