Lock session during deserialization (#19310)

Change-Id: I0f0c029d6de88b74bae1c7253b7665d5570e3767

server/src/com/vaadin/server/VaadinSession.java

@@ -18,6 +18,7 @@ package com.vaadin.server;
 
 import java.io.IOException;
 import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.io.Serializable;
 import java.lang.reflect.Method;
 import java.util.Collection;
@@ -1419,6 +1420,26 @@ public class VaadinSession implements HttpSessionBindingListener, Serializable {
         }
     }
 
+    /**
+     * Override default serialization logic to avoid
+     * ConcurrentModificationException if the contents are modified while
+     * serialization is reading them.
+     */
+    private void writeObject(ObjectOutputStream out) throws IOException {
+        Lock lock = this.lock;
+
+        if (lock != null) {
+            lock.lock();
+        }
+        try {
+            out.defaultWriteObject();
+        } finally {
+            if (lock != null) {
+                lock.unlock();
+            }
+        }
+    }
+
     /**
      * Finds the UI with the corresponding embed id.
      *

server/tests/src/com/vaadin/server/VaadinSessionTest.java

@@ -20,6 +20,7 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
+import java.io.Serializable;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.locks.Lock;
@@ -42,17 +43,17 @@ import com.vaadin.ui.Label;
 import com.vaadin.ui.UI;
 import com.vaadin.util.CurrentInstance;
 
-public class VaadinSessionTest {
+public class VaadinSessionTest implements Serializable {
 
-    private VaadinSession session;
-    private VaadinServlet mockServlet;
-    private VaadinServletService mockService;
-    private ServletConfig mockServletConfig;
-    private HttpSession mockHttpSession;
-    private WrappedSession mockWrappedSession;
-    private VaadinServletRequest vaadinRequest;
-    private UI ui;
-    private Lock httpSessionLock;
+    private transient VaadinSession session;
+    private transient VaadinServlet mockServlet;
+    private transient VaadinServletService mockService;
+    private transient ServletConfig mockServletConfig;
+    private transient HttpSession mockHttpSession;
+    private transient WrappedSession mockWrappedSession;
+    private transient VaadinServletRequest vaadinRequest;
+    private transient UI ui;
+    private transient Lock httpSessionLock;
 
     @Before
     public void setup() throws Exception {
@@ -316,4 +317,27 @@ public class VaadinSessionTest {
                 deserializedSession, deserializedLabel.session);
         deserializedSession.unlock();
     }
+
+    @Test
+    public void lockedDuringSerialization() throws IOException {
+        final AtomicBoolean lockChecked = new AtomicBoolean(false);
+
+        ui.setContent(new Label() {
+            private void writeObject(ObjectOutputStream out) throws IOException {
+                Assert.assertTrue(session.hasLock());
+                lockChecked.set(true);
+                out.defaultWriteObject();
+            }
+        });
+
+        session.unlock();
+        Assert.assertFalse(session.hasLock());
+
+        ObjectOutputStream out = new ObjectOutputStream(
+                new ByteArrayOutputStream());
+        out.writeObject(session);
+
+        Assert.assertFalse(session.hasLock());
+        Assert.assertTrue(lockChecked.get());
+    }
 }