Adjust handling of resolved action command object

When the view provider's getViewName() method is called twice with the same viewAndParameters argument, the corresponding result is returned right away for the second invocation if an action command object was determined in the first invocation. An exception will only be thrown if there is already a view object available but has not yet been requested via getView() and a different viewAndParameters argument is passed into getViewName().

This fixes an issue which the add-on had with Vaadin 7.7 and 8.0.

src/main/java/org/vaadin/uriactions/ActionExecutionView.java

@@ -19,19 +19,17 @@
  */
 public class ActionExecutionView implements View {
     private final UriActionCommand command;
-    private final UriFragmentActionNavigatorWrapper uriFragmentActionNavigatorWrapper;
 
-    ActionExecutionView(final UriFragmentActionNavigatorWrapper uriFragmentActionNavigatorWrapper, final UriActionCommand command) {
-        Preconditions.checkNotNull(command);
-        Preconditions.checkNotNull(uriFragmentActionNavigatorWrapper);
+    ActionExecutionView(final UriActionCommand command) {
+        if (command == null) {
+            throw new IllegalArgumentException("action command object must not be null");
+        }
         this.command = command;
-        this.uriFragmentActionNavigatorWrapper = uriFragmentActionNavigatorWrapper;
     }
 
     @Override
     public void enter(final ViewChangeListener.ViewChangeEvent event) {
         command.run();
-        uriFragmentActionNavigatorWrapper.resetCurrentActionCommand();
     }
 
     /**

src/main/java/org/vaadin/uriactions/UriFragmentActionNavigatorWrapper.java

@@ -87,7 +87,6 @@ public class UriFragmentActionNavigatorWrapper {
      */
     private final Navigator navigator;
     private UriActionMapperTree uriActionMapperTree;
-    private UriActionCommand currentActionCommandObject;
     private Object routingContext;
 
     /**
@@ -197,13 +196,6 @@ public void setRoutingContext(final Object routingContext) {
         this.routingContext = routingContext;
     }
 
-    /**
-     * Sets the current action command object to null.
-     */
-    void resetCurrentActionCommand() {
-        currentActionCommandObject = null;
-    }
-
     /**
      * {@link ViewDisplay} which delegates the task to display the current {@link View} to a wrapped {@link ViewDisplay}
      * if the {@link View} to be shown is <em>not</em> of type {@link ActionExecutionView}. The wrapped {@link
@@ -232,24 +224,39 @@ public void showView(final View view) {
      * fragment could successfully be resolved.
      */
     private class UriActionViewProvider implements ViewProvider {
+        private ActionExecutionView currentView;
+        private String currentNavigationState;
+
         @Override
         public String getViewName(final String viewAndParameters) {
             if (uriActionMapperTree == null) {
                 return null;
             }
+            if (currentView != null && currentNavigationState != null) {
+                if (currentNavigationState.equals(viewAndParameters)) {
+                    return viewAndParameters;
+                } else {
+                    throw new IllegalStateException(
+                            "Access synchronization problem: this action navigator is currently handling another request. " +
+                                    "Currently handled navigation state is: " + currentNavigationState +
+                                    ". Current action is: " + currentView.getUriActionCommand());
+                }
+            }
+
             final UriActionCommand action = uriActionMapperTree.interpretFragment(viewAndParameters, routingContext, false);
-            if (currentActionCommandObject != null) {
-                throw new IllegalStateException(
-                        "Thread synchronization problem: this action navigator is currently handling another request. Current action is: "
-                                + currentActionCommandObject);
+            if (action != null) {
+                currentView = new ActionExecutionView(action);
+                currentNavigationState = viewAndParameters;
             }
-            currentActionCommandObject = action;
             return action != null ? viewAndParameters : null;
         }
 
         @Override
         public View getView(final String viewName) {
-            return new ActionExecutionView(UriFragmentActionNavigatorWrapper.this, currentActionCommandObject);
+            View returnedView = currentView;
+            currentNavigationState = null;
+            currentView = null;
+            return returnedView;
         }
     }
 }