diff --git a/src/com/hellogithub/servlet/retLabelServlet.java b/src/com/hellogithub/servlet/retLabelServlet.java
index dcf5223..d9386ef 100644
--- a/src/com/hellogithub/servlet/retLabelServlet.java
+++ b/src/com/hellogithub/servlet/retLabelServlet.java
@@ -38,8 +38,14 @@ public class retLabelServlet extends HttpServlet {
         resp.setHeader("Access-Control-Allow-Headers", "access-control-allow-origin, authority, content-type, version-info, X-Requested-With");
         resp.setContentType("application/json;charset=UTF-8");
         PrintWriter writer = resp.getWriter();
-        String jsonString = JSONObject.toJSONString(categoryService.retLabel());
-        writer.println(jsonString);
+        if(categoryService.retLabel().size() !=0)
+        {
+            String jsonString = JSONObject.toJSONString(categoryService.retLabel());
+            writer.println(jsonString);
+        }
+        else{
+            writer.println("null");
+        }
         writer.close();
     }
     public void setResult(Integer code, String msg, PrintWriter writer) {