diff --git a/Survey/src/java/servlet/Ml1.java b/Survey/src/java/servlet/Ml1.java
index 37f854941c247fe11c84e49811669350d61e12dc..30c1b3c4a6c791c79e24f2f7187aef1b36c3ddfc 100644
--- a/Survey/src/java/servlet/Ml1.java
+++ b/Survey/src/java/servlet/Ml1.java
@@ -50,7 +50,6 @@ public class Ml1 extends HttpServlet {
             Integer urlNum = Integer.parseInt(request.getParameter("urlNum"));
             HttpSession session = request.getSession(true);
             String currentUser = (String) session.getAttribute("currentSessionUser");
-            System.out.println(currentUser);
             String url = (String) session.getAttribute("1url" + urlNum + currentUser);
             URL MLurl = new URL(url);
             InputStream is = (InputStream) MLurl.getContent();
@@ -69,30 +68,32 @@ public class Ml1 extends HttpServlet {
             String info = (String) jsonObj.get("infoLinks");
             out.println(message);
 
-            //write info and percentexper to the logging file
-            String path = request.getRealPath("/User");
-            String oldFileName = path + "/" + currentUser + ".txt";
-            String tempFileName = path + "/" + "temp.txt";
-            BufferedReader newBr;
-            BufferedWriter bw;
-            String newLine;
-            newBr = new BufferedReader(new FileReader(oldFileName));
-            bw = new BufferedWriter(new FileWriter(tempFileName));
-            if (!"null".equals(currentUser)) {
-                while ((newLine = newBr.readLine()) != null) {
-                    if (newLine.contains(url)) {
-                        newLine = newLine.replace("<info></info>", "<info>" + info + "</info>").replace("<percentexper></percentexper>", "<percentexper>" + percentexper + "</percentexper>");
+            if (currentUser != null) {
+                //write info and percentexper to the logging file
+                String path = request.getRealPath("/User");
+                String oldFileName = path + "/" + currentUser + ".txt";
+                String tempFileName = path + "/" + "temp.txt";
+                BufferedReader newBr;
+                BufferedWriter bw;
+                String newLine;
+                newBr = new BufferedReader(new FileReader(oldFileName));
+                bw = new BufferedWriter(new FileWriter(tempFileName));
+                if (!"null".equals(currentUser)) {
+                    while ((newLine = newBr.readLine()) != null) {
+                        if (newLine.contains(url)) {
+                            newLine = newLine.replace("<info></info>", "<info>" + info + "</info>").replace("<percentexper></percentexper>", "<percentexper>" + percentexper + "</percentexper>");
+                        }
+                        bw.write(newLine + "\n");
                     }
-                    bw.write(newLine + "\n");
                 }
-            }
-            newBr.close();
-            bw.close();
+                newBr.close();
+                bw.close();
 
-            File oldFile = new File(oldFileName);
-            oldFile.delete();
-            File newFile = new File(tempFileName);
-            newFile.renameTo(oldFile);
+                File oldFile = new File(oldFileName);
+                oldFile.delete();
+                File newFile = new File(tempFileName);
+                newFile.renameTo(oldFile);
+            }
         } finally {
             out.close();
         }
diff --git a/Survey/src/java/servlet/Ml3.java b/Survey/src/java/servlet/Ml3.java
index 4ab2296325f8a75c8f806371a7143b742729545a..0664dc655415b261330f5e6e0c6913b3bd7743d0 100644
--- a/Survey/src/java/servlet/Ml3.java
+++ b/Survey/src/java/servlet/Ml3.java
@@ -68,29 +68,30 @@ public class Ml3 extends HttpServlet {
             String info = (String) jsonObj.get("infoLinks");
             out.println(message);
 
-            String path = request.getRealPath("/User");
-            String oldFileName = path + "/" + currentUser + ".txt";
-            String tempFileName = path + "/" + "temp.txt";
-            BufferedReader newBr;
-            BufferedWriter bw;
-            String newLine;
-            newBr = new BufferedReader(new FileReader(oldFileName));
-            bw = new BufferedWriter(new FileWriter(tempFileName));
-            if (!"null".equals(currentUser)) {
+            if (currentUser != null) {
+                String path = request.getRealPath("/User");
+                String oldFileName = path + "/" + currentUser + ".txt";
+                String tempFileName = path + "/" + "temp.txt";
+                BufferedReader newBr;
+                BufferedWriter bw;
+                String newLine;
+                newBr = new BufferedReader(new FileReader(oldFileName));
+                bw = new BufferedWriter(new FileWriter(tempFileName));
+
                 while ((newLine = newBr.readLine()) != null) {
                     if (newLine.contains(url)) {
                         newLine = newLine.replace("<info></info>", "<info>" + info + "</info>").replace("<percentexper></percentexper>", "<percentexper>" + percentexper + "</percentexper>");
                     }
                     bw.write(newLine + "\n");
                 }
-            }
-            newBr.close();
-            bw.close();
+                newBr.close();
+                bw.close();
 
-            File oldFile = new File(oldFileName);
-            oldFile.delete();
-            File newFile = new File(tempFileName);
-            newFile.renameTo(oldFile);
+                File oldFile = new File(oldFileName);
+                oldFile.delete();
+                File newFile = new File(tempFileName);
+                newFile.renameTo(oldFile);
+            }
         } finally {
             out.close();
         }