vaadin
diff --git a/‎flow-server/src/main/java/com/vaadin/flow/server/streams/AbstractFileUploadHandler.java
Lines changed: 5 additions & 2 deletions b/‎flow-server/src/main/java/com/vaadin/flow/server/streams/AbstractFileUploadHandler.java
Lines changed: 5 additions & 2 deletions
diff --git a/‎flow-server/src/main/java/com/vaadin/flow/server/streams/InMemoryUploadHandler.java
Lines changed: 5 additions & 2 deletions b/‎flow-server/src/main/java/com/vaadin/flow/server/streams/InMemoryUploadHandler.java
Lines changed: 5 additions & 2 deletions
diff --git a/‎flow-server/src/test/java/com/vaadin/flow/server/communication/UploadHandlerTest.java
Lines changed: 16 additions & 2 deletions b/‎flow-server/src/test/java/com/vaadin/flow/server/communication/UploadHandlerTest.java
Lines changed: 16 additions & 2 deletions
diff --git a/‎flow-server/src/test/java/com/vaadin/flow/server/streams/UploadTransferProgressTest.java
Lines changed: 1 addition & 0 deletions b/‎flow-server/src/test/java/com/vaadin/flow/server/streams/UploadTransferProgressTest.java
Lines changed: 1 addition & 0 deletions
@@ -69,8 +69,11 @@ public void handleUploadRequest(UploadEvent event) throws IOException {
             notifyError(event, e);
             throw e;
         }
-        successHandler.accept(new UploadMetadata(event.getFileName(),
-                event.getContentType(), event.getFileSize()), file);
+        event.getUI()
+                .access(() -> successHandler.accept(
+                        new UploadMetadata(event.getFileName(),
+                                event.getContentType(), event.getFileSize()),
+                        file));
     }
 
     @Override
 
@@ -53,8 +53,11 @@ public void handleUploadRequest(UploadEvent event) throws IOException {
             notifyError(event, e);
             throw e;
         }
-        successHandler.accept(new UploadMetadata(event.getFileName(),
-                event.getContentType(), event.getFileSize()), data);
+        event.getUI()
+                .access(() -> successHandler.accept(
+                        new UploadMetadata(event.getFileName(),
+                                event.getContentType(), event.getFileSize()),
+                        data));
     }
 
     @Override
 
@@ -9,6 +9,7 @@
 import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.Future;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -32,6 +33,7 @@
 import com.vaadin.flow.internal.CurrentInstance;
 import com.vaadin.flow.internal.StateNode;
 import com.vaadin.flow.server.AbstractStreamResource;
+import com.vaadin.flow.server.Command;
 import com.vaadin.flow.server.HttpStatusCode;
 import com.vaadin.flow.server.MockVaadinServletService;
 import com.vaadin.flow.server.MockVaadinSession;
@@ -84,12 +86,24 @@ public class UploadHandlerTest {
     @Before
     public void setUp() throws ServletException, ServiceException {
         VaadinService service = new MockVaadinServletService();
+        ui = new MockUI() {
+            @Override
+            public Future<Void> access(Command command) {
+                command.execute();
+                return null;
+            }
+        };
 
         session = new AlwaysLockedVaadinSession(service) {
             @Override
             public StreamResourceRegistry getResourceRegistry() {
                 return streamResourceRegistry;
             }
+
+            @Override
+            public UI getUIById(int uiId) {
+                return ui;
+            }
         };
         streamResourceRegistry = new StreamResourceRegistry(session);
         request = Mockito.mock(VaadinServletRequest.class);
@@ -102,8 +116,6 @@ public StreamResourceRegistry getResourceRegistry() {
         element = Mockito.
DED0
mock(Element.class);
         Mockito.when(element.getNode()).thenReturn(stateNode);
         response = Mockito.mock(VaadinResponse.class);
-        ui = new MockUI();
-        UI.setCurrent(ui);
     }
 
     @After
@@ -199,6 +211,8 @@ public void accept(UploadMetadata uploadMetadata,
         mockRequest(res, testString);
 
         handler.handleRequest(session, request, response);
+        session.getPendingAccessQueue()
+                .forEach(futureAccess -> futureAccess.run());
 
         Assert.assertArrayEquals("Output differed from expected", testBytes,
                 output);
 
@@ -127,6 +127,7 @@ public StreamResourceRegistry getResourceRegistry() {
             command.execute();
             return null;
         }).when(ui).access(Mockito.any(Command.class));
+        Mockito.when(uploadEvent.getUI()).thenReturn(ui);
 
         Mockito.when(componentOwner.getUI()).thenReturn(Optional.of(ui));
         Mockito.when(uploadEvent.getOwningComponent())
Original file line number	Diff line number	Diff line change
`@@ -69,8 +69,11 @@ public void handleUploadRequest(UploadEvent event) throws IOException {`
`69`	`69`	`notifyError(event, e);`
`70`	`70`	`throw e;`
`71`	`71`	`}`
`72`		`- successHandler.accept(new UploadMetadata(event.getFileName(),`
`73`		`- event.getContentType(), event.getFileSize()), file);`
	`72`	`+ event.getUI()`
	`73`	`+ .access(() -> successHandler.accept(`
	`74`	`+ new UploadMetadata(event.getFileName(),`
	`75`	`+ event.getContentType(), event.getFileSize()),`
	`76`	`+ file));`
`74`	`77`	`}`
`75`	`78`
`76`	`79`	`@Override`
Original file line number	Diff line number	Diff line change
`@@ -53,8 +53,11 @@ public void handleUploadRequest(UploadEvent event) throws IOException {`
`53`	`53`	`notifyError(event, e);`
`54`	`54`	`throw e;`
`55`	`55`	`}`
`56`		`- successHandler.accept(new UploadMetadata(event.getFileName(),`
`57`		`- event.getContentType(), event.getFileSize()), data);`
	`56`	`+ event.getUI()`
	`57`	`+ .access(() -> successHandler.accept(`
	`58`	`+ new UploadMetadata(event.getFileName(),`
	`59`	`+ event.getContentType(), event.getFileSize()),`
	`60`	`+ data));`
`58`	`61`	`}`
`59`	`62`
`60`	`63`	`@Override`