diff --git a/src/main/java/org/gcube/datatransfer/resolver/http/HttpResolver.java b/src/main/java/org/gcube/datatransfer/resolver/http/HttpResolver.java
index 84cb81b..bead527 100644
--- a/src/main/java/org/gcube/datatransfer/resolver/http/HttpResolver.java
+++ b/src/main/java/org/gcube/datatransfer/resolver/http/HttpResolver.java
@@ -24,13 +24,16 @@ import org.slf4j.LoggerFactory;
 /**
  * 
  * @author Andrea Manzi(CERN)
+ * updated by Francesco Mangiacrapa
+ * 
  *
  */
 public class HttpResolver extends HttpServlet {
 	
-	String uri =null;
-	String fileName =null;
-	String contentType =null;
+	protected static final String SMP_URI = "smp-uri";
+	protected static final String VALIDATION = "validation";
+	protected static final String CONTENT_TYPE = "contentType";
+	protected static final String FILE_NAME = "fileName";
 
 	private static final long serialVersionUID = 1L;
 
@@ -44,14 +47,15 @@ public class HttpResolver extends HttpServlet {
 	}
 
 	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
-	
-
-		logger.info("The http session id is: " + request.getSession().getId());
 		
-		logger.debug("Original URI = "+ uri);
+		String uri =null;
+		String fileName =null;
+		String contentType =null;
+		boolean validatingURI = false;
 
-		
-		uri = request.getParameter("smp-uri");
+//		logger.info("The http session id is: " + request.getSession().getId());
+
+		uri = request.getParameter(SMP_URI);
 
 		if (uri == null || uri.equals("")) {
 			logger.debug("URI not found");
@@ -59,7 +63,7 @@ public class HttpResolver extends HttpServlet {
 			return;
 		}
 		
-		fileName  = request.getParameter("fileName");
+		fileName  = request.getParameter(FILE_NAME);
 		
 		
 		if (fileName == null || fileName.equals("")) {
@@ -67,13 +71,17 @@ public class HttpResolver extends HttpServlet {
 			fileName = null;
 		}
 
-		contentType  = request.getParameter("contentType");
+		contentType  = request.getParameter(CONTENT_TYPE);
 		
 		if (contentType == null || contentType.equals("")) {
 			logger.debug("contentType not found");
 			contentType = null;
 		}
 		
+		String validation = request.getParameter(VALIDATION);
+		validatingURI = Boolean.parseBoolean(validation);
+		logger.debug("validation? "+validatingURI);
+		
 		//we should not unescape the filename with spaces
 		
 		int index= uri.indexOf("?");
@@ -123,8 +131,27 @@ public class HttpResolver extends HttpServlet {
 				logger.error("URLConnection Exception:", e);
 				return;
 			}
+			
+			//CASE InputStream NULL
+			if(in==null){
+				logger.warn("Input stream is null, sending status error 404");
+				sendErrorQuietly(response, 404);
+				return;
+			}
 
-
+			//CASE VALIDATION
+			if(validatingURI){
+				byte[] bytes = new byte[1]; //1B
+				int c = in.read(bytes);
+				logger.info(c+" byte read from InputStream");
+				if(c>0){
+					logger.info("at least 1 byte read, returning status 200");
+					IOUtils.closeQuietly(in);
+					response.setStatus(200);
+					return;
+				}	
+			}
+	
 			/*
 			IOUtils.copy(in, out);
 		
@@ -133,8 +160,6 @@ public class HttpResolver extends HttpServlet {
 			in.close();
 			*/
 			
-			if(in!=null)
-			
 			//CHANGED BY FRANCESCO M.
 			try {
 				
@@ -148,7 +173,7 @@ public class HttpResolver extends HttpServlet {
 					throw e; //Sending Exceptions
 				
 			}	catch (NullPointerException e) {
-				logger.warn("NullPointerException: input stream is null, skipping printStrackTrace");
+				logger.warn("NullPointerException during copy, skipping printStrackTrace");
 				sendErrorQuietly(response, 404);
 				
 			} finally {
@@ -171,6 +196,7 @@ public class HttpResolver extends HttpServlet {
 		if(response!=null){
 			try {
 				response.sendError(code);
+				logger.info("Response sent error: "+code);
 			} catch (IOException ioe) {
 				 // ignore
 			}