Add shorthands for locking the session (#10225)

Change-Id: Ic2f3843a48a6e26af848208e9495473853146fbe

3 files changed, 72 insertions, 24 deletions

diff --git a/server/src/com/vaadin/server/AbstractCommunicationManager.java b/server/src/com/vaadin/server/AbstractCommunicationManager.java
index 731d83067e..31920b5df6 100644
--- a/server/src/com/vaadin/server/AbstractCommunicationManager.java
+++ b/server/src/com/vaadin/server/AbstractCommunicationManager.java
@@ -297,12 +297,12 @@ public abstract class AbstractCommunicationManager implements Serializable {
                 cleanStreamVariable(owner, variableName);
             }
         } catch (Exception e) {
-            session.getLock().lock();
+            session.lock();
             try {
                 handleChangeVariablesError(session, (Component) owner, e,
                         new HashMap<String, Object>());
             } finally {
-                session.getLock().unlock();
+                session.unlock();
             }
         }
         sendUploadResponse(request, response);
@@ -345,12 +345,12 @@ public abstract class AbstractCommunicationManager implements Serializable {
                 cleanStreamVariable(owner, variableName);
             }
         } catch (Exception e) {
-            session.getLock().lock();
+            session.lock();
             try {
                 handleChangeVariablesError(session, (Component) owner, e,
                         new HashMap<String, Object>());
             } finally {
-                session.getLock().unlock();
+                session.unlock();
             }
         }
         sendUploadResponse(request, response);
@@ -382,13 +382,13 @@ public abstract class AbstractCommunicationManager implements Serializable {
                 filename, type, contentLength);
         try {
             boolean listenProgress;
-            session.getLock().lock();
+            session.lock();
             try {
                 streamVariable.streamingStarted(startedEvent);
                 out = streamVariable.getOutputStream();
                 listenProgress = streamVariable.listenProgress();
             } finally {
-                session.getLock().unlock();
+                session.unlock();
             }
 
             // Gets the output target stream
@@ -409,13 +409,13 @@ public abstract class AbstractCommunicationManager implements Serializable {
                 if (listenProgress) {
                     // update progress if listener set and contentLength
                     // received
-                    session.getLock().lock();
+                    session.lock();
                     try {
                         StreamingProgressEventImpl progressEvent = new StreamingProgressEventImpl(
                                 filename, type, contentLength, totalBytes);
                         streamVariable.onProgress(progressEvent);
                     } finally {
-                        session.getLock().unlock();
+                        session.unlock();
                     }
                 }
                 if (streamVariable.isInterrupted()) {
@@ -427,11 +427,11 @@ public abstract class AbstractCommunicationManager implements Serializable {
             out.close();
             StreamingEndEvent event = new StreamingEndEventImpl(filename, type,
                     totalBytes);
-            session.getLock().lock();
+            session.lock();
             try {
                 streamVariable.streamingFinished(event);
             } finally {
-                session.getLock().unlock();
+                session.unlock();
             }
 
         } catch (UploadInterruptedException e) {
@@ -439,17 +439,17 @@ public abstract class AbstractCommunicationManager implements Serializable {
             tryToCloseStream(out);
             StreamingErrorEvent event = new StreamingErrorEventImpl(filename,
                     type, contentLength, totalBytes, e);
-            session.getLock().lock();
+            session.lock();
             try {
                 streamVariable.streamingFailed(event);
             } finally {
-                session.getLock().unlock();
+                session.unlock();
             }
             // Note, we are not throwing interrupted exception forward as it is
             // not a terminal level error like all other exception.
         } catch (final Exception e) {
             tryToCloseStream(out);
-            session.getLock().lock();
+            session.lock();
             try {
                 StreamingErrorEvent event = new StreamingErrorEventImpl(
                         filename, type, contentLength, totalBytes, e);
@@ -458,7 +458,7 @@ public abstract class AbstractCommunicationManager implements Serializable {
                 // terminalErrorHandler)
                 throw new UploadException(e);
             } finally {
-                session.getLock().unlock();
+                session.unlock();
             }
         }
         return startedEvent.isDisposed();
@@ -571,7 +571,7 @@ public abstract class AbstractCommunicationManager implements Serializable {
         // The rest of the process is synchronized with the session
         // in order to guarantee that no parallel variable handling is
         // made
-        session.getLock().lock();
+        session.lock();
         try {
 
             // Verify that there's an UI
@@ -606,7 +606,7 @@ public abstract class AbstractCommunicationManager implements Serializable {
                     outWriter, uI, analyzeLayouts);
             postPaint(uI);
         } finally {
-            session.getLock().unlock();
+            session.unlock();
         }
 
         outWriter.close();
@@ -2439,7 +2439,7 @@ public abstract class AbstractCommunicationManager implements Serializable {
     public void handleBrowserDetailsRequest(VaadinRequest request,
             VaadinResponse response, VaadinSession session) throws IOException {
 
-        session.getLock().lock();
+        session.lock();
 
         try {
             assert UI.getCurrent() == null;
@@ -2468,7 +2468,7 @@ public abstract class AbstractCommunicationManager implements Serializable {
             // TODO Auto-generated catch block
             e.printStackTrace();
         } finally {
-            session.getLock().unlock();
+            session.unlock();
         }
     }
 
diff --git a/server/src/com/vaadin/server/VaadinService.java b/server/src/com/vaadin/server/VaadinService.java
index a4caf6cdd6..41115a3503 100644
--- a/server/src/com/vaadin/server/VaadinService.java
+++ b/server/src/com/vaadin/server/VaadinService.java
@@ -642,14 +642,14 @@ public abstract class VaadinService implements Serializable {
         int uiId = Integer.parseInt(uiIdString);
 
         // Get lock before accessing data in session
-        session.getLock().lock();
+        session.lock();
         try {
             UI ui = session.getUIById(uiId);
 
             UI.setCurrent(ui);
             return ui;
         } finally {
-            session.getLock().unlock();
+            session.unlock();
         }
     }
 
diff --git a/server/src/com/vaadin/server/VaadinSession.java b/server/src/com/vaadin/server/VaadinSession.java
index 74e3bd360d..3fc75b67f4 100644
--- a/server/src/com/vaadin/server/VaadinSession.java
+++ b/server/src/com/vaadin/server/VaadinSession.java
@@ -743,16 +743,64 @@ public class VaadinSession implements HttpSessionBindingListener, Serializable {
     }
 
     /**
-     * Gets the lock that should be used to synchronize usage of data inside
-     * this session.
+     * Gets the {@link Lock} instance that is used for protecting the data of
+     * this session from concurrent access.
+     * <p>
+     * The <code>Lock</code> can be used to gain more control than what is
+     * available only using {@link #lock()} and {@link #unlock()}. The returned
+     * instance is not guaranteed to support any other features of the
+     * <code>Lock</code> interface than {@link Lock#lock()} and
+     * {@link Lock#unlock()}.
+     * 
+     * @return the <code>Lock</code> that is used for synchronization, never
+     *         <code>null</code>
      * 
-     * @return the lock that should be used for synchronization
+     * @see #lock()
+     * @see Lock
      */
-    public Lock getLock() {
+    public Lock getLockInstance() {
         return lock;
     }
 
     /**
+     * Locks this session to protect its data from concurrent access. Accessing
+     * the UI state from outside the normal request handling should always lock
+     * the session and unlock it when done. To ensure that the lock is always
+     * released, you should typically wrap the code in a <code>try</code> block
+     * and unlock the session in <code>finally</code>:
+     * 
+     * <pre>
+     * session.lock();
+     * try {
+     *     doSomething();
+     * } finally {
+     *     session.unlock();
+     * }
+     * </pre>
+     * <p>
+     * This method will block until the lock can be retrieved.
+     * <p>
+     * {@link #getLockInstance()} can be used if more control over the locking
+     * is required.
+     * 
+     * @see #unlock()
+     * @see #getLockInstance()
+     */
+    public void lock() {
+        getLockInstance().lock();
+    }
+
+    /**
+     * Unlocks this session. This method should always be used in a finally
+     * block after {@link #lock()} to ensure that the lock is always released.
+     * 
+     * @see #unlock()
+     */
+    public void unlock() {
+        getLockInstance().unlock();
+    }
+
+    /**
      * Stores a value in this service session. This can be used to associate
      * data with the current user so that it can be retrieved at a later point
      * from some other part of the application. Setting the value to