SPR-5452: Content negotiation

org.springframework.web.servlet/src/main/java/org/springframework/web/servlet/view/ContentNegotiatingViewResolver.java

@@ -0,0 +1,310 @@
+/*
+ * Copyright 2002-2009 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.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.SortedMap;
+import java.util.TreeMap;
+import javax.activation.FileTypeMap;
+import javax.activation.MimetypesFileTypeMap;
+import javax.servlet.ServletContext;
+import javax.servlet.http.HttpServletRequest;
+
+import org.springframework.beans.factory.BeanFactoryUtils;
+import org.springframework.core.OrderComparator;
+import org.springframework.core.Ordered;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.MediaType;
+import org.springframework.util.StringUtils;
+import org.springframework.web.context.request.RequestAttributes;
+import org.springframework.web.context.request.RequestContextHolder;
+import org.springframework.web.context.request.ServletRequestAttributes;
+import org.springframework.web.context.support.WebApplicationObjectSupport;
+import org.springframework.web.servlet.View;
+import org.springframework.web.servlet.ViewResolver;
+import org.springframework.web.util.UrlPathHelper;
+import org.springframework.web.util.WebUtils;
+
+/**
+ * Implementation of {@link ViewResolver} that resolves a view based on the request file name or {@code Accept} header.
+ *
+ * <p>The {@code ContentNegotiatingViewResolver} does not resolve views itself, but delegates to other {@link
+ * ViewResolver}s. By default, these other view resolvers are picked up automatically from the application context,
+ * though they can also be set explicitely by using the {@link #setViewResolvers(List) viewResolvers} property.
+ * <strong>Note</strong> that in order for this view resolver to work properly, the {@link #setOrder(int) order}
+ * property needs to be set to a higher precedence than the others (the default is {@link Ordered#HIGHEST_PRECEDENCE}.)
+ *
+ * <p>This view resolver uses the requested {@linkplain MediaType media type} to select a suitable {@link View} for a
+ * request. This media type is determined by using the following criteria:
+ * <ol>
+ * <li>If the requested path has a file extension and if the {@link #setFavorPathExtension(boolean)} property is
+ * <code>true</code>, the {@link #setMediaTypes(Map)  mediaTypes} property is inspected for a matching media type.</li>
+ * <li>If there is no match and if the Java Activation Framework (JAF) is present on the class path,
+ * {@link FileTypeMap#getContentType(String)} is used.</li>
+ * <li>If the previous steps did not result in a media type, the request {@code Accept} header is used.</li>
+ * </ol>
+ * Once the requested media type has been determined, this resolver queries each delegate view resolver for a
+ * {@link View} and determines if the requested media type is {@linkplain MediaType#includes(MediaType) compatible} with
+ * the view's {@linkplain View#getContentType() content type}). The most compatible view is returned.
+ *
+ * <p>For example, if the request path is {@code /view.html}, this view resolver will look for a view that has the
+ * {@code text/html} content type (based on the {@code html} file extension). A request for {@code /view} with a {@code
+ * text/html} request {@code Accept} header has the same result.
+ *
+ * @author Arjen Poutsma
+ * @see ViewResolver
+ * @see InternalResourceViewResolver
+ * @see BeanNameViewResolver
+ * @since 3.0
+ */
+public class ContentNegotiatingViewResolver extends WebApplicationObjectSupport implements ViewResolver, Ordered {
+
+	private static final boolean jafPresent =
+			ClassUtils.isPresent("javax.activation.FileTypeMap", ContentNegotiatingViewResolver.class.getClassLoader());
+
+	private static final String ACCEPT_HEADER = "Accept";
+
+	private UrlPathHelper urlPathHelper = new UrlPathHelper();
+
+	private boolean favorPathExtension = true;
+
+	private int order = Ordered.HIGHEST_PRECEDENCE;
+
+	private Map<String, MediaType> mediaTypes = new HashMap<String, MediaType>();
+
+	private List<ViewResolver> viewResolvers;
+
+	public void setOrder(int order) {
+		this.order = order;
+	}
+
+	public int getOrder() {
+		return order;
+	}
+
+	/**
+	 * Indicates whether the extension of the request path should be used to determine the requested media type, in favor
+	 * of looking at the {@code Accept} header.
+	 *
+	 * <p>For instance, when this flag is <code>true</code> (the default), a request for {@code /hotels.pdf} will result in
+	 * an {@code AbstractPdfView} being resolved, while the {@code Accept} header can be the browser-defined {@code
+	 * text/html,application/xhtml+xml}.
+	 */
+	public void setFavorPathExtension(boolean favorPathExtension) {
+		this.favorPathExtension = favorPathExtension;
+	}
+
+	/**
+	 * Sets the mapping from file extensions to media types.
+	 *
+	 * <p>When this mapping is not set or when an extension is not present, this view resolver will fall back to using a
+	 * {@link FileTypeMap} when the Java Action Framework is available.
+	 */
+	public void setMediaTypes(Map<String, String> mediaTypes) {
+		Assert.notNull(mediaTypes, "'mediaTypes' must not be null");
+		for (Map.Entry<String, String> entry : mediaTypes.entrySet()) {
+			String extension = entry.getKey().toLowerCase(Locale.ENGLISH);
+			MediaType mediaType = MediaType.parseMediaType(entry.getValue());
+			this.mediaTypes.put(extension, mediaType);
+		}
+	}
+
+	/**
+	 * Sets the view resolvers to be wrapped by this view resolver.
+	 *
+	 * <p>If this property is not set, view resolvers will be detected automatically.
+	 */
+	public void setViewResolvers(List<ViewResolver> viewResolvers) {
+		this.viewResolvers = viewResolvers;
+	}
+
+	@Override
+	protected void initServletContext(ServletContext servletContext) {
+		if (viewResolvers == null) {
+			Map<String, ViewResolver> matchingBeans = BeanFactoryUtils
+					.beansOfTypeIncludingAncestors(getApplicationContext(), ViewResolver.class, true, false);
+			this.viewResolvers = new ArrayList<ViewResolver>(matchingBeans.size());
+			for (ViewResolver viewResolver : matchingBeans.values()) {
+				if (this != viewResolver) {
+					this.viewResolvers.add(viewResolver);
+				}
+			}
+		}
+		if (this.viewResolvers.isEmpty()) {
+			logger.warn("Did not find any ViewResolvers to delegate to; please configure them using the " +
+					"'viewResolvers' property on the ContentNegotiatingViewResolver");
+		}
+		Collections.sort(this.viewResolvers, new OrderComparator());
+	}
+
+	/**
+	 * Determines the list of {@link MediaType} for the given {@link HttpServletRequest}.
+	 *
+	 * <p>The default implementation invokes {@link #getMediaTypeFromFilename(String)} if {@linkplain
+	 * #setFavorPathExtension(boolean) favorPathExtension} property is <code>true</code>. If the property is
+	 * <code>false</code>, or when a media type cannot be determined from the request path, this method will inspect the
+	 * {@code Accept} header of the request.
+	 *
+	 * <p>This method can be overriden to provide a different algorithm.
+	 *
+	 * @param request the current servlet request
+	 * @return the list of media types requested, if any
+	 */
+	protected List<MediaType> getMediaTypes(HttpServletRequest request) {
+		if (favorPathExtension) {
+			String requestUri = urlPathHelper.getRequestUri(request);
+			String filename = WebUtils.extractFullFilenameFromUrlPath(requestUri);
+			MediaType mediaType = getMediaTypeFromFilename(filename);
+			if (mediaType != null) {
+				if (logger.isDebugEnabled()) {
+					logger.debug("Requested media type is '" + mediaType + "' (based on filename '" + filename + "')");
+				}
+				List<MediaType> mediaTypes = new ArrayList<MediaType>();
+				mediaTypes.add(mediaType);
+				return mediaTypes;
+			}
+		}
+		String acceptHeader = request.getHeader(ACCEPT_HEADER);
+		if (StringUtils.hasText(acceptHeader)) {
+			List<MediaType> mediaTypes = MediaType.parseMediaTypes(acceptHeader);
+			if (logger.isDebugEnabled()) {
+				logger.debug("Requested media types are " + mediaTypes + " (based on Accept header)");
+			}
+			return mediaTypes;
+		}
+		else {
+			return Collections.emptyList();
+		}
+	}
+
+	/**
+	 * Determines the {@link MediaType} for the given filename.
+	 *
+	 * <p>The default implementation will check the {@linkplain #setMediaTypes(Map) media types} property first for a
+	 * defined mapping. If not present, and if the Java Activation Framework can be found on the class path, it will call
+	 * {@link FileTypeMap#getContentType(String)}
+	 *
+	 * <p>This method can be overriden to provide a different algorithm.
+	 *
+	 * @param filename the current request file name (i.e. {@code hotels.html})
+	 * @return the media type, if any
+	 */
+	protected MediaType getMediaTypeFromFilename(String filename) {
+		String extension = StringUtils.getFilenameExtension(filename);
+		if (!StringUtils.hasText(extension)) {
+			return null;
+		}
+		extension = extension.toLowerCase(Locale.ENGLISH);
+		MediaType mediaType = mediaTypes.get(extension);
+		if (mediaType == null && jafPresent) {
+			mediaType = ActivationMediaTypeFactory.getMediaType(filename);
+			if (mediaType != null) {
+				mediaTypes.put(extension, mediaType);
+			}
+		}
+		return mediaType;
+	}
+
+	public View resolveViewName(String viewName, Locale locale) throws Exception {
+		RequestAttributes attrs = RequestContextHolder.getRequestAttributes();
+		Assert.isInstanceOf(ServletRequestAttributes.class, attrs);
+		ServletRequestAttributes servletAttrs = (ServletRequestAttributes) attrs;
+		List<MediaType> requestedMediaTypes = getMediaTypes(servletAttrs.getRequest());
+		Collections.sort(requestedMediaTypes);
+
+		SortedMap<MediaType, View> views = new TreeMap<MediaType, View>();
+		for (ViewResolver viewResolver : viewResolvers) {
+			View view = viewResolver.resolveViewName(viewName, locale);
+			if (view != null) {
+				MediaType viewMediaType = MediaType.parseMediaType(view.getContentType());
+				for (MediaType requestedMediaType : requestedMediaTypes) {
+					if (requestedMediaType.includes(viewMediaType)) {
+						if (!views.containsKey(requestedMediaType)) {
+							views.put(requestedMediaType, view);
+							break;
+						}
+					}
+				}
+			}
+		}
+		if (!views.isEmpty()) {
+			MediaType mediaType = views.firstKey();
+			View view = views.get(mediaType);
+			if (logger.isDebugEnabled()) {
+				logger.debug("Returning [" + view + "] based on requested media type '" + mediaType + "'");
+			}
+			return view;
+		}
+		else {
+			return null;
+		}
+	}
+
+	/**
+	 * Inner class to avoid hard-coded JAF dependency.
+	 */
+	private static class ActivationMediaTypeFactory {
+
+		private static final FileTypeMap fileTypeMap;
+
+		static {
+			fileTypeMap = loadFileTypeMapFromContextSupportModule();
+		}
+
+		private static FileTypeMap loadFileTypeMapFromContextSupportModule() {
+			// see if we can find the extended mime.types from the context-support module
+			Resource mappingLocation = new ClassPathResource("org/springframework/mail/javamail/mime.types");
+			if (mappingLocation.exists()) {
+				InputStream inputStream = null;
+				try {
+					inputStream = mappingLocation.getInputStream();
+					return new MimetypesFileTypeMap(inputStream);
+				}
+				catch (IOException ex) {
+					// ignore
+				}
+				finally {
+					if (inputStream != null) {
+						try {
+							inputStream.close();
+						}
+						catch (IOException ex) {
+							// ignore
+						}
+					}
+				}
+			}
+			return FileTypeMap.getDefaultFileTypeMap();
+		}
+
+		public static MediaType getMediaType(String fileName) {
+			String mediaType = fileTypeMap.getContentType(fileName);
+			return StringUtils.hasText(mediaType) ? MediaType.parseMediaType(mediaType) : null;
+		}
+	}
+
+}

org.springframework.web.servlet/src/test/java/org/springframework/web/servlet/view/ContentNegotiatingViewResolverTests.java

@@ -0,0 +1,144 @@
+/*
+ * Copyright 2002-2009 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.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Locale;
+
+import static org.easymock.EasyMock.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.mock.web.MockHttpServletRequest;
+import org.springframework.util.MediaType;
+import org.springframework.web.context.request.RequestContextHolder;
+import org.springframework.web.context.request.ServletRequestAttributes;
+import org.springframework.web.servlet.View;
+import org.springframework.web.servlet.ViewResolver;
+
+/** @author Arjen Poutsma */
+public class ContentNegotiatingViewResolverTests {
+
+	private ContentNegotiatingViewResolver viewResolver;
+
+	@Before
+	public void createViewResolver() {
+		viewResolver = new ContentNegotiatingViewResolver();
+	}
+
+	@Test
+	public void getMediaTypeFromFilename() {
+		assertEquals("Invalid content type", new MediaType("text", "html"),
+				viewResolver.getMediaTypeFromFilename("test.html"));
+		viewResolver.setMediaTypes(Collections.singletonMap("HTML", "application/xhtml+xml"));
+		assertEquals("Invalid content type", new MediaType("application", "xhtml+xml"),
+				viewResolver.getMediaTypeFromFilename("test.html"));
+	}
+
+	@Test
+	public void getMediaTypeFilename() {
+		MockHttpServletRequest request = new MockHttpServletRequest("GET", "/test.html?foo=bar");
+		List<MediaType> result = viewResolver.getMediaTypes(request);
+		assertEquals("Invalid content type", Collections.singletonList(new MediaType("text", "html")), result);
+		viewResolver.setMediaTypes(Collections.singletonMap("html", "application/xhtml+xml"));
+		result = viewResolver.getMediaTypes(request);
+		assertEquals("Invalid content type", Collections.singletonList(new MediaType("application", "xhtml+xml")),
+				result);
+	}
+
+	@Test
+	public void getMediaTypeAcceptHeader() {
+		MockHttpServletRequest request = new MockHttpServletRequest("GET", "/test");
+		request.addHeader("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");
+		List<MediaType> result = viewResolver.getMediaTypes(request);
+		assertEquals("Invalid amount of media types", 4, result.size());
+		assertEquals("Invalid content type", new MediaType("text", "html"), result.get(0));
+		assertEquals("Invalid content type", new MediaType("application", "xhtml+xml"), result.get(1));
+		assertEquals("Invalid content type", new MediaType("application", "xml", Collections.singletonMap("q", "0.9")),
+				result.get(2));
+		assertEquals("Invalid content type", new MediaType("*", "*", Collections.singletonMap("q", "0.8")),
+				result.get(3));
+	}
+
+	@Test
+	public void resolveViewNameAcceptHeader() throws Exception {
+		MockHttpServletRequest request = new MockHttpServletRequest("GET", "/test");
+		request.addHeader("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8");
+		RequestContextHolder.setRequestAttributes(new ServletRequestAttributes(request));
+
+		ViewResolver viewResolverMock1 = createMock(ViewResolver.class);
+		ViewResolver viewResolverMock2 = createMock(ViewResolver.class);
+		List<ViewResolver> viewResolverMocks = new ArrayList<ViewResolver>();
+		viewResolverMocks.add(viewResolverMock1);
+		viewResolverMocks.add(viewResolverMock2);
+		viewResolver.setViewResolvers(viewResolverMocks);
+
+		View viewMock1 = createMock("application_xml", View.class);
+		View viewMock2 = createMock("text_html", View.class);
+
+		String viewName = "view";
+		Locale locale = Locale.ENGLISH;
+
+		expect(viewResolverMock1.resolveViewName(viewName, locale)).andReturn(viewMock1);
+		expect(viewResolverMock2.resolveViewName(viewName, locale)).andReturn(viewMock2);
+		expect(viewMock1.getContentType()).andReturn("application/xml");
+		expect(viewMock2.getContentType()).andReturn("text/html;charset=ISO-8859-1");
+
+		replay(viewResolverMock1, viewResolverMock2, viewMock1, viewMock2);
+
+		View result = viewResolver.resolveViewName(viewName, locale);
+		assertSame("Invalid view", viewMock2, result);
+
+		verify(viewResolverMock1, viewResolverMock2, viewMock1, viewMock2);
+	}
+	
+	@Test
+	public void resolveViewNameFilename() throws Exception {
+		MockHttpServletRequest request = new MockHttpServletRequest("GET", "/test.html");
+		RequestContextHolder.setRequestAttributes(new ServletRequestAttributes(request));
+
+		ViewResolver viewResolverMock1 = createMock(ViewResolver.class);
+		ViewResolver viewResolverMock2 = createMock(ViewResolver.class);
+		List<ViewResolver> viewResolverMocks = new ArrayList<ViewResolver>();
+		viewResolverMocks.add(viewResolverMock1);
+		viewResolverMocks.add(viewResolverMock2);
+		viewResolver.setViewResolvers(viewResolverMocks);
+
+		View viewMock1 = createMock("application_xml", View.class);
+		View viewMock2 = createMock("text_html", View.class);
+
+		String viewName = "view";
+		Locale locale = Locale.ENGLISH;
+
+		expect(viewResolverMock1.resolveViewName(viewName, locale)).andReturn(viewMock1);
+		expect(viewResolverMock2.resolveViewName(viewName, locale)).andReturn(viewMock2);
+		expect(viewMock1.getContentType()).andReturn("application/xml");
+		expect(viewMock2.getContentType()).andReturn("text/html;charset=ISO-8859-1");
+
+		replay(viewResolverMock1, viewResolverMock2, viewMock1, viewMock2);
+
+		View result = viewResolver.resolveViewName(viewName, locale);
+		assertSame("Invalid view", viewMock2, result);
+
+		verify(viewResolverMock1, viewResolverMock2, viewMock1, viewMock2);
+	}
+
+}