Detect changes in parent flow definitions

Issue: SWF-1662

spring-webflow/src/main/java/org/springframework/webflow/engine/model/builder/xml/XmlFlowModelBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2004-2012 the original author or authors.
+ * Copyright 2004-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 package org.springframework.webflow.engine.model.builder.xml;
 
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;
@@ -52,6 +53,8 @@ import org.springframework.webflow.engine.model.VarModel;
 import org.springframework.webflow.engine.model.ViewStateModel;
 import org.springframework.webflow.engine.model.builder.FlowModelBuilder;
 import org.springframework.webflow.engine.model.builder.FlowModelBuilderException;
+import org.springframework.webflow.engine.model.registry.FlowModelHolder;
+import org.springframework.webflow.engine.model.registry.FlowModelHolderLocator;
 import org.springframework.webflow.engine.model.registry.FlowModelLocator;
 import org.springframework.webflow.engine.model.registry.NoSuchFlowModelException;
 import org.w3c.dom.Document;
@@ -63,6 +66,7 @@ import org.xml.sax.SAXException;
  *
  * @author Keith Donald
  * @author Scott Andrews
+ * @author Rossen Stoyanchev
  */
 public class XmlFlowModelBuilder implements FlowModelBuilder {
 
@@ -78,6 +82,8 @@ public class XmlFlowModelBuilder implements FlowModelBuilder {
 
 	private FlowModel flowModel;
 
+	private final List<FlowModelHolder> parentHolders = new ArrayList<FlowModelHolder>(4);
+
 	/**
 	 * Create a new XML flow model builder that will parse the XML document at the specified resource location and use
 	 * the provided locator to access parent flow models.
@@ -157,6 +163,11 @@ public class XmlFlowModelBuilder implements FlowModelBuilder {
 			if (lastModified > lastModifiedTimestamp) {
 				return true;
 			} else {
+				for (FlowModelHolder parent : this.parentHolders) {
+					if (parent.hasFlowModelChanged()) {
+						return true;
+					}
+				}
 				return false;
 			}
 		} catch (IOException e) {
@@ -635,6 +646,14 @@ public class XmlFlowModelBuilder implements FlowModelBuilder {
 						throw new FlowModelBuilderException("Unable to find flow '" + parentFlowId
 								+ "' to inherit from", e);
 					}
+					try {
+						if (this.modelLocator instanceof FlowModelHolderLocator) {
+							FlowModelHolderLocator locator = (FlowModelHolderLocator) this.modelLocator;
+							this.parentHolders.add(locator.getFlowModelHolder(parentFlowId));
+						}
+					} catch (NoSuchFlowModelException e) {
+						// Ignore
+					}
 				}
 			}
 		}

spring-webflow/src/main/java/org/springframework/webflow/engine/model/registry/FlowModelHolderLocator.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2004-2015 the original author or authors.
+ *
+ * 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 org.springframework.webflow.engine.model.registry;
+
+/**
+ * A companion to {@link FlowModelLocator} for access to the FlowModelHolder
+ * wrapping the FlowModel.
+ *
+ * @author Rossen Stoyanchev
+ * @since 2.4.2
+ */
+public interface FlowModelHolderLocator {
+
+	/**
+	 * Lookup the FlowModelHolder with the specified id.
+	 * @param id the flow model identifier
+	 * @return the flow model holder
+	 * @throws NoSuchFlowModelException when the flow model with the specified
+	 * id does not exist
+	 */
+	public FlowModelHolder getFlowModelHolder(String id) throws NoSuchFlowModelException;
+
+}

spring-webflow/src/main/java/org/springframework/webflow/engine/model/registry/FlowModelRegistryImpl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2004-2012 the original author or authors.
+ * Copyright 2004-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,8 +27,9 @@ import org.springframework.webflow.engine.model.FlowModel;
  * 
  * @author Keith Donald
  * @author Scott Andrews
+ * @author Rossen Stoyanchev
  */
-public class FlowModelRegistryImpl implements FlowModelRegistry {
+public class FlowModelRegistryImpl implements FlowModelRegistry, FlowModelHolderLocator {
 
 	/**
 	 * The map of loaded Flow models maintained in this registry.
@@ -48,7 +49,7 @@ public class FlowModelRegistryImpl implements FlowModelRegistry {
 
 	public FlowModel getFlowModel(String id) throws NoSuchFlowModelException {
 		try {
-			return getFlowModelHolder(id).getFlowModel();
+			return getLocalFlowModelHolder(id).getFlowModel();
 		} catch (NoSuchFlowModelException e) {
 			if (parent != null) {
 				// try parent
@@ -69,12 +70,25 @@ public class FlowModelRegistryImpl implements FlowModelRegistry {
 		flowModels.put(id, modelHolder);
 	}
 
+	// implementing FlowModelHolderLocator
+
+	public FlowModelHolder getFlowModelHolder(String id) throws NoSuchFlowModelException {
+		try {
+			return getLocalFlowModelHolder(id);
+		} catch (NoSuchFlowModelException e) {
+			if (parent != null && parent instanceof FlowModelHolderLocator) {
+				return ((FlowModelHolderLocator) parent).getFlowModelHolder(id);
+			}
+			throw e;
+		}
+	}
+
 	// internal helpers
 
 	/**
 	 * Returns the identified flow model holder. Throws an exception if it cannot be found.
 	 */
-	private FlowModelHolder getFlowModelHolder(String id) throws NoSuchFlowModelException {
+	private FlowModelHolder getLocalFlowModelHolder(String id) throws NoSuchFlowModelException {
 		FlowModelHolder holder = flowModels.get(id);
 		if (holder == null) {
 			throw new NoSuchFlowModelException(id);