ZK-3729: getDesktop() sometimes returns NULL causing NPE

zk/src/main/java/org/zkoss/zk/ui/impl/SimpleDesktopCache.java

@@ -17,6 +17,7 @@
 package org.zkoss.zk.ui.impl;
 
 import java.util.ArrayList;
+import java.util.List;
 import java.util.Timer;
 import java.util.TimerTask;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -241,6 +242,20 @@ public void stop() {
 		}
 	}
 
+	public List<Desktop> getAllDesktops() {
+		final boolean old = _desktops.disableExpunge(true);
+
+		try {
+			ArrayList<Desktop> desktops = null;
+			synchronized (_desktops) {
+				desktops = new ArrayList<Desktop>(_desktops.values());
+			}
+			return desktops;
+		} finally {
+			_desktops.disableExpunge(old);
+		}
+	}
+
 	/** Holds desktops. */
 	private static class Cache extends CacheMap<String, Desktop> { //serializable
 		private AtomicBoolean _expungeDisabled = new AtomicBoolean(false);

zk/src/main/java/org/zkoss/zk/ui/impl/UiEngineImpl.java

@@ -98,6 +98,7 @@
 import org.zkoss.zk.ui.sys.Attributes;
 import org.zkoss.zk.ui.sys.ComponentCtrl;
 import org.zkoss.zk.ui.sys.ComponentsCtrl;
+import org.zkoss.zk.ui.sys.DesktopCache;
 import org.zkoss.zk.ui.sys.DesktopCtrl;
 import org.zkoss.zk.ui.sys.EventProcessingThread;
 import org.zkoss.zk.ui.sys.ExecutionCtrl;
@@ -2123,8 +2124,26 @@ private static final void doDeactivate(Execution exec) {
 		}
 
 		final SessionCtrl sessCtrl = (SessionCtrl) desktop.getSession();
-		if (sessCtrl.isInvalidated())
-			sessCtrl.invalidateNow();
+
+		if (sessCtrl.isInvalidated()) {
+
+			// Fix ZK-3729, only invalidate if there is no working desktop in the session.
+			DesktopCache desktopCache = sessCtrl.getDesktopCache();
+			boolean hasWorkingDesktop = false;
+			if (desktopCache != null) {
+				List<Desktop> allDesktops = desktopCache.getAllDesktops();
+
+				for (Desktop d : allDesktops) {
+					if (d != desktop && d.getExecution() != null) {
+						hasWorkingDesktop = true;
+						break;
+					}
+				}
+			}
+
+			if (!hasWorkingDesktop)
+				sessCtrl.invalidateNow();
+		}
 	}
 
 	/** Re-activates for another execution. It is callable only for

zk/src/main/java/org/zkoss/zk/ui/sys/DesktopCache.java

@@ -1,9 +1,9 @@
 /* DesktopCache.java
 
 	Purpose:
-		
+
 	Description:
-		
+
 	History:
 		Tue Apr 18 10:38:22     2006, Created by tomyeh
 
@@ -16,6 +16,8 @@
 */
 package org.zkoss.zk.ui.sys;
 
+import java.util.List;
+
 import org.zkoss.zk.ui.ComponentNotFoundException;
 import org.zkoss.zk.ui.Desktop;
 import org.zkoss.zk.ui.Session;
@@ -65,4 +67,10 @@ public interface DesktopCache {
 	 * {@link DesktopCacheProvider}.
 	 */
 	public void stop();
+
+	/** Returns all the desktops in this cache.
+	 * It is used only internally.
+	 * @since 10.1.0
+	 */
+	public List<Desktop> getAllDesktops();
 }

zkdoc/release-note

@@ -18,6 +18,7 @@ ZK 10.1.0
   ZK-5743: clicking menuitem fires 2 onClick events in mobile browser
   ZK-5594: ListboxDataLoader doGroupsDataChange finds incorrect offset, causes class cast exception
   ZK-5475: select a date with time produces an invalid result under locale pt
+  ZK-3729: getDesktop() sometimes returns NULL causing NPE
 
 * Upgrade Notes
   + Remove Htmls.encodeJavaScript(), Strings.encodeJavaScript(), Strings.escape() with Strings.ESCAPE_JAVASCRIPT, and replace them with OWASP Java Encoder APIs instead.

zktest/src/main/java/org/zkoss/zktest/test2/B101_ZK_3729Composer.java

@@ -0,0 +1,58 @@
+/* B101_ZK_3729Composer.java
+
+	Purpose:
+
+	Description:
+
+	History:
+		3:36 PM 2024/9/18, Created by jumperchen
+
+Copyright (C) 2024 Potix Corporation. All Rights Reserved.
+*/
+package org.zkoss.zktest.test2;
+
+import org.zkoss.zk.ui.Component;
+import org.zkoss.zk.ui.Sessions;
+import org.zkoss.zk.ui.event.Events;
+import org.zkoss.zk.ui.select.SelectorComposer;
+import org.zkoss.zk.ui.select.annotation.Listen;
+import org.zkoss.zk.ui.select.annotation.Wire;
+import org.zkoss.zul.Div;
+import org.zkoss.zul.Grid;
+import org.zkoss.zul.ListModelList;
+
+/**
+ * @author jumperchen
+ */
+public class B101_ZK_3729Composer extends SelectorComposer {
+
+	@Wire private Grid grid;
+	private Div rootDiv;
+	private ListModelList model = new ListModelList();
+
+	@Override
+	public void doAfterCompose(Component comp) throws Exception {
+		super.doAfterCompose(comp);
+		rootDiv = (Div) comp;
+		grid.setModel(model);
+	}
+
+	@Listen(Events.ON_CLICK + "=#logout")
+	public void logout() {
+		Sessions.getCurrent().invalidate();
+		//        ((SimpleSession)Sessions.getCurrent()).invalidateNow();
+	}
+
+	@Listen(Events.ON_CLICK + "=#op2")
+	public void longOp() {
+		fakeOperation(3);
+		model.add("success");
+	}
+
+	static public void fakeOperation(int seconds) {
+		long endTime = System.currentTimeMillis() + seconds * 1000;
+		while (System.currentTimeMillis() < endTime) {
+			// Just a busy-wait. In real scenarios, this could be some meaningful computation.
+		}
+	}
+}

zktest/src/main/webapp/test2/B101-ZK-3729.zul

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!--
+B101-ZK-3729.zul
+
+	Purpose:
+
+	Description:
+
+	History:
+		2024/9/18, Created by jumperchen
+
+Copyright (C) 2024 Potix Corporation. All Rights Reserved.
+
+-->
+<zk>
+	<div apply="org.zkoss.zktest.test2.B101_ZK_3729Composer">
+		<button id="op2" label="sync long op"/>
+		<button id="logout" label="logout" />
+		<grid id="grid"></grid>
+	</div>
+</zk>

zktest/src/main/webapp/test2/config.properties

@@ -3137,6 +3137,7 @@ B90-ZK-4431.zul=A,E,Multislider
 ##zats##B101-ZK-5743.zul=A,E,Compressed,JS,Debug-JS,TabletUI,Mobile,onClick
 ##zats##B101-ZK-5594.zul=A,E,Group,ListGroup,ROD,zkmax,Exception
 ##zats##B101-ZK-5475.zul=A,E,Datebox,PT,Locale,Format,Constraint
+##zats##B101-ZK-3729.zul=A,E,Desktop,Session,Timeout,NPE,Multithreading
 
 ##
 # Features - 3.0.x version

zktest/src/test/java/org/zkoss/zktest/zats/test2/B101_ZK_3729Test.java

@@ -0,0 +1,39 @@
+/* B101_ZK_3729Test.java
+
+	Purpose:
+
+	Description:
+
+	History:
+		11:25 AM 2024/9/19, Created by jumperchen
+
+Copyright (C) 2024 Potix Corporation. All Rights Reserved.
+*/
+package org.zkoss.zktest.zats.test2;
+
+import org.junit.jupiter.api.Test;
+import org.openqa.selenium.WindowType;
+
+import org.zkoss.test.webdriver.WebDriverTestCase;
+
+/**
+ * @author jumperchen
+ */
+public class B101_ZK_3729Test extends WebDriverTestCase {
+
+	@Test
+	public void test() {
+		connect();
+		driver.switchTo().newWindow(WindowType.TAB);
+		driver.get(getAddress() + "/test2/B101-ZK-3729.zul");
+		waitResponse();
+		Object[] windowHandles = driver.getWindowHandles().toArray();
+		driver.switchTo().window((String) windowHandles[0]);
+		click(jq("$op2"));
+		driver.switchTo().window((String) windowHandles[1]);
+		click(jq("$logout"));
+		driver.switchTo().window((String) windowHandles[0]);
+		waitResponse();
+		assertNoZKError();
+	}
+}