Iterate over copies of listener lists (#17477)

Allows adding/removing view change listeners from listeners.

Change-Id: Idb2227e1423c0297887f01f6df03b74e633ad917

server/src/com/vaadin/navigator/Navigator.java

@@ -32,6 +32,7 @@ package com.vaadin.navigator;
  */
 
 import java.io.Serializable;
+import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
@@ -597,7 +598,10 @@ public class Navigator implements Serializable {
      *         block the navigation operation
      */
     protected boolean fireBeforeViewChange(ViewChangeEvent event) {
-        for (ViewChangeListener l : listeners) {
+        // a copy of the listener list is needed to avoid
+        // ConcurrentModificationException as a listener can add/remove
+        // listeners
+        for (ViewChangeListener l : new ArrayList<ViewChangeListener>(listeners)) {
             if (!l.beforeViewChange(event)) {
                 return false;
             }
@@ -647,7 +651,10 @@ public class Navigator implements Serializable {
      *            view change event (not null)
      */
     protected void fireAfterViewChange(ViewChangeEvent event) {
-        for (ViewChangeListener l : listeners) {
+        // a copy of the listener list is needed to avoid
+        // ConcurrentModificationException as a listener can add/remove
+        // listeners
+        for (ViewChangeListener l : new ArrayList<ViewChangeListener>(listeners)) {
             l.afterViewChange(event);
         }
     }

uitest/src/com/vaadin/tests/navigator/NavigatorListenerModifiesListeners.java

@@ -0,0 +1,100 @@
+package com.vaadin.tests.navigator;
+
+import com.vaadin.navigator.Navigator;
+import com.vaadin.navigator.View;
+import com.vaadin.navigator.ViewChangeListener;
+import com.vaadin.navigator.ViewChangeListener.ViewChangeEvent;
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.Button;
+import com.vaadin.ui.Button.ClickEvent;
+import com.vaadin.ui.Button.ClickListener;
+import com.vaadin.ui.Label;
+import com.vaadin.ui.VerticalLayout;
+
+public class NavigatorListenerModifiesListeners extends AbstractTestUI {
+
+    private Navigator navigator;
+
+    protected static final String LABEL_MAINVIEW_ID = "LABEL_MAINVIEW_ID";
+    protected static final String LABEL_ANOTHERVIEW_ID = "LABEL_ANOTHERVIEW_ID";
+
+    // NOP view change listener
+    private class MyViewChangeListener implements ViewChangeListener {
+        @Override
+        public boolean beforeViewChange(ViewChangeEvent event) {
+            navigator.removeViewChangeListener(listener1);
+            navigator.addViewChangeListener(listener2);
+            return true;
+        }
+
+        @Override
+        public void afterViewChange(ViewChangeEvent event) {
+            navigator.removeViewChangeListener(listener2);
+            navigator.addViewChangeListener(listener1);
+        }
+    }
+
+    private MyViewChangeListener listener1 = new MyViewChangeListener();
+    private MyViewChangeListener listener2 = new MyViewChangeListener();
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        navigator = new Navigator(this, this);
+        navigator.addView(MainView.NAME, new MainView());
+        navigator.addView(AnotherView.NAME, new AnotherView());
+        navigator.addViewChangeListener(listener1);
+        navigator.navigateTo(MainView.NAME);
+    }
+
+    class MainView extends VerticalLayout implements View {
+
+        public static final String NAME = "mainview";
+
+        public MainView() {
+            Label label = new Label("MainView content");
+            label.setId(LABEL_MAINVIEW_ID);
+            addComponent(label);
+
+            Button buttonNavToAnotherView = new Button(
+                    "Navigate to another view", new ClickListener() {
+
+                        @Override
+                        public void buttonClick(ClickEvent event) {
+                            navigator.navigateTo(AnotherView.NAME);
+                        }
+                    });
+            addComponent(buttonNavToAnotherView);
+        }
+
+        @Override
+        public void enter(ViewChangeEvent event) {
+        }
+
+    }
+
+    class AnotherView extends VerticalLayout implements View {
+
+        public static final String NAME = "another";
+
+        public AnotherView() {
+            Label label = new Label("AnotherView content");
+            label.setId(LABEL_ANOTHERVIEW_ID);
+            addComponent(label);
+        }
+
+        @Override
+        public void enter(ViewChangeEvent event) {
+        }
+    }
+
+    @Override
+    protected String getTestDescription() {
+        return "Adding and removing view change listeners from view change listeners should not cause a ConcurrentModificationException";
+    }
+
+    @Override
+    protected Integer getTicketNumber() {
+        return 17477;
+    }
+}

uitest/src/com/vaadin/tests/navigator/NavigatorListenerModifiesListenersTest.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2000-2014 Vaadin Ltd.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.tests.navigator;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import org.openqa.selenium.By;
+import org.openqa.selenium.WebElement;
+
+import com.vaadin.testbench.elements.ButtonElement;
+import com.vaadin.tests.tb3.SingleBrowserTest;
+
+public class NavigatorListenerModifiesListenersTest extends SingleBrowserTest {
+
+    @Test
+    public void testIfConfirmBack() {
+        openTestURL();
+
+        // keep URL of main view
+        final String initialUrl = driver.getCurrentUrl();
+
+        // do it 2 times to verify that this is not broken after first time
+        for (int i = 0; i < 2; i++) {
+            // go to prompted view
+            WebElement button = $(ButtonElement.class).first();
+            button.click();
+
+            // verify we are in another view and url is correct
+            waitForElementPresent(By
+                    .id(NavigatorListenerModifiesListeners.LABEL_ANOTHERVIEW_ID));
+            String currentUrl = driver.getCurrentUrl();
+            assertEquals(
+                    "Current URL should be equal to another view URL",
+                    initialUrl
+                            .replace(
+                                    NavigatorListenerModifiesListeners.MainView.NAME,
+                                    NavigatorListenerModifiesListeners.AnotherView.NAME),
+                    currentUrl);
+
+            // click back button
+            driver.navigate().back();
+
+            // verify we are in main view and url is correct
+            // without the fix for #17477, we get
+            // ConcurrentModificationException
+            waitForElementPresent(By
+                    .id(NavigatorListenerModifiesListeners.LABEL_MAINVIEW_ID));
+            currentUrl = driver.getCurrentUrl();
+            assertEquals("Current URL should be equal to the initial view URL",
+                    initialUrl, currentUrl);
+        }
+    }
+
+}