Add filter to AbstractCachingViewResolver

This commit introduces a filter that specifies whether a View should be
cached by the AbstractCachingViewResolver or not.

Closes gh-22391

Author: fred84

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

@@ -68,6 +68,9 @@ public void render(@Nullable Map<String, ?> model, HttpServletRequest request, H
 	/** Fast access cache for Views, returning already cached instances without a global lock. */
 	private final Map<Object, View> viewAccessCache = new ConcurrentHashMap<>(DEFAULT_CACHE_LIMIT);
 
+	/** Filter function which determines if view should be cached. */
+	private ViewCacheFilter viewCacheFilter = (viewName, view, locale) -> true;
+
 	/** Map from view key to View instance, synchronized for View creation. */
 	@SuppressWarnings("serial")
 	private final Map<Object, View> viewCreationCache =
@@ -134,6 +137,21 @@ public void setCacheUnresolved(boolean cacheUnresolved) {
 		this.cacheUnresolved = cacheUnresolved;
 	}
 
+	/**
+	 * Filter function which determines if view should be cached.
+	 * Default behaviour is to cache all views.
+	 */
+	public void setViewCacheFilter(ViewCacheFilter cacheFilter) {
+		this.viewCacheFilter = cacheFilter;
+	}
+
+	/**
+	 * Return filter function which determines if view should be cached.
+	 */
+	public ViewCacheFilter getViewCacheFilter() {
+		return this.viewCacheFilter;
+	}
+
 	/**
 	 * Return if caching of unresolved views is enabled.
 	 */
@@ -160,7 +178,7 @@ public View resolveViewName(String viewName, Locale locale) throws Exception {
 						if (view == null && this.cacheUnresolved) {
 							view = UNRESOLVED_VIEW;
 						}
-						if (view != null) {
+						if (view != null && this.viewCacheFilter.filter(viewName, view, locale)) {
 							this.viewAccessCache.put(cacheKey, view);
 							this.viewCreationCache.put(cacheKey, view);
 						}

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

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2002-2018 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.web.servlet.view;
+
+import java.util.Locale;
+
+import org.springframework.web.servlet.View;
+
+/**
+ * Filter which determines if view should be cached in {@link AbstractCachingViewResolver}.
+ *
+ * @author Sergey Galkin
+ */
+@FunctionalInterface
+public interface ViewCacheFilter {
+
+	boolean filter(String viewName, View view, Locale locale);
+}

spring-webmvc/src/test/java/org/springframework/web/servlet/view/ViewResolverCacheFilterTest.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2002-2018 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.web.servlet.view;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.Locale;
+import org.junit.Test;
+import org.springframework.web.servlet.View;
+
+public class ViewResolverCacheFilterTest {
+
+	private interface ViewLoader {
+		View load(String viewName);
+	}
+
+	private static class TestViewResolver extends AbstractCachingViewResolver {
+
+		private final ViewLoader viewLoader;
+
+		private TestViewResolver(ViewLoader viewLoader) {
+			this.viewLoader = viewLoader;
+		}
+
+		@Override
+		protected View loadView(String viewName, Locale locale) {
+			return viewLoader.load(viewName);
+		}
+	}
+
+	private final static String VIEW_NAME = "name";
+	private final ViewLoader viewLoader = mock(ViewLoader.class);
+	private final TestViewResolver resolver = new TestViewResolver(viewLoader);
+
+	@Test
+	public void viewWillBePlacedInCache() throws Exception {
+		resolver.setViewCacheFilter((n, v, l) -> true);
+
+		resolver.resolveViewName(VIEW_NAME, Locale.ENGLISH);
+		resolver.resolveViewName(VIEW_NAME, Locale.ENGLISH);
+
+		verify(viewLoader, times(1)).load(any());
+	}
+
+	@Test
+	public void viewWillNotBePlacedInCached() throws Exception {
+		resolver.setViewCacheFilter((n, v, l) -> false);
+
+		resolver.resolveViewName(VIEW_NAME, Locale.ENGLISH);
+		resolver.resolveViewName(VIEW_NAME, Locale.ENGLISH);
+
+		verify(viewLoader, times(2)).load(any());
+	}
+
+	@Test
+	public void verifyPassedParamsToFilter() throws Exception {
+		View view = mock(View.class);
+		when(viewLoader.load(any())).thenReturn(view);
+
+		ViewCacheFilter filter = mock(ViewCacheFilter.class);
+		resolver.setViewCacheFilter(filter);
+
+		resolver.resolveViewName(VIEW_NAME, Locale.ENGLISH);
+
+		verify(filter, times(1)).filter(eq(VIEW_NAME), eq(view), eq(Locale.ENGLISH));
+	}
+}