TilesConfigurer defensively expects null from getResources in case of no resources found

Also includes order preservation for resource results with Tiles 2 as well as retrieval failure logging with Tiles 3.

Issue: SPR-12362
(cherry picked from commit c8b8dc5)

Author: jhoeller

spring-webmvc-tiles3/src/main/java/org/springframework/web/servlet/view/tiles3/SpringWildcardServletTilesApplicationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -37,6 +37,7 @@
  * Spring-specific subclass of the Tiles ServletApplicationContext.
  *
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  * @since 3.2
  */
 public class SpringWildcardServletTilesApplicationContext extends ServletApplicationContext {
@@ -77,24 +78,26 @@ public Collection<ApplicationResource> getResources(String path) {
 			resources = this.resolver.getResources(path);
 		}
 		catch (IOException ex) {
-			return Collections.<ApplicationResource> emptyList();
+			((ServletContext) getContext()).log("Resource retrieval failed for path: " + path, ex);
+			return Collections.emptyList();
 		}
-		Collection<ApplicationResource> resourceList = new ArrayList<ApplicationResource>();
-		if (!ObjectUtils.isEmpty(resources)) {
-			for (Resource resource : resources) {
-				URL url;
-				try {
-					url = resource.getURL();
-					resourceList.add(new URLApplicationResource(url.toExternalForm(), url));
-				}
-				catch (IOException ex) {
-					// shouldn't happen with the kind of resources we're using
-					throw new IllegalArgumentException("No URL for " + resource.toString(), ex);
-				}
+		if (ObjectUtils.isEmpty(resources)) {
+			((ServletContext) getContext()).log("No resources found for path pattern: " + path);
+			return Collections.emptyList();
+		}
+
+		Collection<ApplicationResource> resourceList = new ArrayList<ApplicationResource>(resources.length);
+		for (Resource resource : resources) {
+			try {
+				URL url = resource.getURL();
+				resourceList.add(new URLApplicationResource(url.toExternalForm(), url));
+			}
+			catch (IOException ex) {
+				// Shouldn't happen with the kind of resources we're using
+				throw new IllegalArgumentException("No URL for " + resource, ex);
 			}
 		}
 		return resourceList;
 	}
 
 }
-

spring-webmvc-tiles3/src/main/java/org/springframework/web/servlet/view/tiles3/TilesConfigurer.java

@@ -16,6 +16,7 @@
 
 package org.springframework.web.servlet.view.tiles3;
 
+import java.util.Collection;
 import java.util.LinkedList;
 import java.util.List;
 import javax.el.ArrayELResolver;
@@ -285,7 +286,10 @@ protected List<ApplicationResource> getSources(ApplicationContext applicationCon
 			if (definitions != null) {
 				List<ApplicationResource> result = new LinkedList<ApplicationResource>();
 				for (String definition : definitions) {
-					result.addAll(applicationContext.getResources(definition));
+					Collection<ApplicationResource> resources = applicationContext.getResources(definition);
+					if (resources != null) {
+						result.addAll(resources);
+					}
 				}
 				return result;
 			}

spring-webmvc/src/main/java/org/springframework/web/servlet/view/tiles2/SpringTilesApplicationContextFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2014 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.
@@ -19,8 +19,8 @@
 import java.io.IOException;
 import java.net.URL;
 import java.util.Enumeration;
-import java.util.HashSet;
 import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
 import javax.servlet.ServletContext;
@@ -32,6 +32,8 @@
 
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.support.ResourcePatternResolver;
+import org.springframework.util.CollectionUtils;
+import org.springframework.util.ObjectUtils;
 import org.springframework.web.context.support.ServletContextResourcePatternResolver;
 
 /**
@@ -89,7 +91,7 @@ public Map<String, String> getInitParams() {
 		public URL getResource(String path) throws IOException {
 			URL retValue = null;
 			Set<URL> urlSet = getResources(path);
-			if (urlSet != null && !urlSet.isEmpty()) {
+			if (!CollectionUtils.isEmpty(urlSet)) {
 				retValue = urlSet.iterator().next();
 			}
 			return retValue;
@@ -99,8 +101,8 @@ public URL getResource(String path) throws IOException {
 		public Set<URL> getResources(String path) throws IOException {
 			Set<URL> urlSet = null;
 			Resource[] resources = this.resolver.getResources(path);
-			if (resources != null && resources.length > 0) {
-				urlSet = new HashSet<URL>();
+			if (!ObjectUtils.isEmpty(resources)) {
+				urlSet = new LinkedHashSet<URL>(resources.length);
 				for (Resource resource : resources) {
 					urlSet.add(resource.getURL());
 				}

spring-webmvc/src/main/java/org/springframework/web/servlet/view/tiles2/TilesConfigurer.java

@@ -25,6 +25,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
+import java.util.Set;
 import javax.servlet.ServletContext;
 import javax.servlet.jsp.JspFactory;
 
@@ -420,7 +421,10 @@ protected List<URL> getSourceURLs(TilesApplicationContext applicationContext,
 				try {
 					List<URL> result = new LinkedList<URL>();
 					for (String definition : definitions) {
-						result.addAll(applicationContext.getResources(definition));
+						Set<URL> resources = applicationContext.getResources(definition);
+						if (resources != null) {
+							result.addAll(resources);
+						}
 					}
 					return result;
 				}