Limit previous solution for non-push mode UI (#11629)

* add test case

* Limit the workaround for non-push mode

Fixes #11616

1 files changed, 8 insertions, 3 deletions

diff --git a/server/src/main/java/com/vaadin/server/communication/FileUploadHandler.java b/server/src/main/java/com/vaadin/server/communication/FileUploadHandler.java
index addf032a83..dbb394cea2 100644
--- a/server/src/main/java/com/vaadin/server/communication/FileUploadHandler.java
+++ b/server/src/main/java/com/vaadin/server/communication/FileUploadHandler.java
@@ -16,8 +16,6 @@
 
 package com.vaadin.server.communication;
 
-import static java.nio.charset.StandardCharsets.UTF_8;
-
 import java.io.BufferedWriter;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -42,6 +40,8 @@ import com.vaadin.shared.ApplicationConstants;
 import com.vaadin.ui.UI;
 import com.vaadin.ui.Upload.FailedEvent;
 
+import static java.nio.charset.StandardCharsets.UTF_8;
+
 /**
  * Handles a file upload request submitted via an Upload component.
  *
@@ -617,7 +617,12 @@ public class FileUploadHandler implements RequestHandler {
             } finally {
                 session.unlock();
             }
-            return true;
+            boolean pushEnabled = UI.getCurrent().getPushConfiguration()
+                    .getPushMode().isEnabled();
+            if (!pushEnabled) {
+                return true;
+            }
+
             // Note, we are not throwing interrupted exception forward as it is
             // not a terminal level error like all other exception.
         } catch (final Exception e) {