/*
* Copyright 2002-2010 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.List;
import java.util.Locale;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import javax.activation.FileTypeMap;
import javax.activation.MimetypesFileTypeMap;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
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.http.MediaType;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.CollectionUtils;
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 explicitly 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}, the {@link #setMediaTypes(Map) mediaTypes} property is inspected for a matching media type.</li>
* <li>If the request contains a parameter defining the extension and if the {@link #setFavorParameter(boolean)}
* property is <code>true</code>, the {@link #setMediaTypes(Map) mediaTypes} property is inspected for a matching
* media type. The default name of the parameter is <code>format</code> and it can be configured using the
* {@link #setParameterName(String) parameterName} property.</li>
* <li>If there is no match in the {@link #setMediaTypes(Map) mediaTypes} property and if the Java Activation
* Framework (JAF) is both {@linkplain #setUseJaf(boolean) enabled} and present on the class path,
* {@link FileTypeMap#getContentType(String)} is used instead.</li>
* <li>If the previous steps did not result in a media type, and
* {@link #setIgnoreAcceptHeader(boolean) ignoreAcceptHeader} is {@code false}, 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>Additionally, this view resolver exposes the {@link #setDefaultViews(List) defaultViews} property, allowing you to
* override the views provided by the view resolvers. Note that these default views are offered as candicates, and
* still need have the content type requested (via file extension, parameter, or {@code Accept} header, described above).
* You can also set the {@linkplain #setDefaultContentType(MediaType) default content type} directly, which will be
* returned when the other mechanisms ({@code Accept} header, file extension or parameter) do not result in a match.
*
* <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
* @author Juergen Hoeller
* @since 3.0
* @see ViewResolver
* @see InternalResourceViewResolver
* @see BeanNameViewResolver
*/
public class ContentNegotiatingViewResolver extends WebApplicationObjectSupport implements ViewResolver, Ordered {
private static final Log logger = LogFactory.getLog(ContentNegotiatingViewResolver.class);
private static final String ACCEPT_HEADER = "Accept";
private static final boolean jafPresent =
ClassUtils.isPresent("javax.activation.FileTypeMap", ContentNegotiatingViewResolver.class.getClassLoader());
private static final UrlPathHelper urlPathHelper = new UrlPathHelper();
private int order = Ordered.HIGHEST_PRECEDENCE;
private boolean favorPathExtension = true;
private boolean favorParameter = false;
private String parameterName = "format";
private boolean useNotAcceptableStatusCode = false;
private boolean ignoreAcceptHeader = false;
private boolean useJaf = true;
private ConcurrentMap<String, MediaType> mediaTypes = new ConcurrentHashMap<String, MediaType>();
private List<View> defaultViews;
private MediaType defaultContentType;
private List<ViewResolver> viewResolvers;
public void setOrder(int order) {
this.order = order;
}
public int getOrder() {
return this.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. The default value is {@code true}.
* <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;
}
/**
* Indicates whether a request parameter should be used to determine the requested media type,
* in favor of looking at the {@code Accept} header. The default value is {@code false}.
* <p>For instance, when this flag is <code>true</code>, a request for {@code /hotels?format=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 setFavorParameter(boolean favorParameter) {
this.favorParameter = favorParameter;
}
/**
* Sets the parameter name that can be used to determine the requested media type if the {@link
* #setFavorParameter(boolean)} property is {@code true}. The default parameter name is {@code format}.
*/
public void setParameterName(String parameterName) {
this.parameterName = parameterName;
}
/**
* Indicates whether the HTTP {@code Accept} header should be ignored. Default is {@code false}.
* If set to {@code true}, this view resolver will only refer to the file extension and/or paramter,
* as indicated by the {@link #setFavorPathExtension(boolean) favorPathExtension} and
* {@link #setFavorParameter(boolean) favorParameter} properties.
*/
public void setIgnoreAcceptHeader(boolean ignoreAcceptHeader) {
this.ignoreAcceptHeader = ignoreAcceptHeader;
}
/**
* Indicates whether a {@link HttpServletResponse#SC_NOT_ACCEPTABLE 406 Not Acceptable} status code should be
* returned if no suitable view can be found.
*
* <p>Default is {@code false}, meaning that this view resolver returns {@code null} for
* {@link #resolveViewName(String, Locale)} when an acceptable view cannot be found. This will allow for view
* resolvers chaining. When this property is set to {@code true},
* {@link #resolveViewName(String, Locale)} will respond with a view that sets the response status to
* {@code 406 Not Acceptable} instead.
*/
public void setUseNotAcceptableStatusCode(boolean useNotAcceptableStatusCode) {
this.useNotAcceptableStatusCode = useNotAcceptableStatusCode;
}
/**
* 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 default views to use when a more specific view can not be obtained
* from the {@link ViewResolver} chain.
*/
public void setDefaultViews(List<View> defaultViews) {
this.defaultViews = defaultViews;
}
/**
* Sets the default content type.
* <p>This content type will be used when file extension, parameter, nor {@code Accept}
* header define a content-type, either through being disabled or empty.
*/
public void setDefaultContentType(MediaType defaultContentType) {
this.defaultContentType = defaultContentType;
}
/**
* Indicates whether to use the Java Activation Framework to map from file extensions to media types.
* <p>Default is {@code true}, i.e. the Java Activation Framework is used (if available).
*/
public void setUseJaf(boolean useJaf) {
this.useJaf = useJaf;
}
/**
* 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 (this.viewResolvers == null) {
Map<String, ViewResolver> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(getApplicationContext(), ViewResolver.class);
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");
}
OrderComparator.sort(this.viewResolvers);
}
/**
* 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 (this.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 + "')");
}
return Collections.singletonList(mediaType);
}
}
if (this.favorParameter) {
if (request.getParameter(this.parameterName) != null) {
String parameterValue = request.getParameter(this.parameterName);
MediaType mediaType = getMediaTypeFromParameter(parameterValue);
if (mediaType != null) {
if (logger.isDebugEnabled()) {
logger.debug("Requested media type is '" + mediaType + "' (based on parameter '" +
this.parameterName + "'='" + parameterValue + "')");
}
return Collections.singletonList(mediaType);
}
}
}
if (!this.ignoreAcceptHeader) {
String acceptHeader = request.getHeader(ACCEPT_HEADER);
if (StringUtils.hasText(acceptHeader)) {
List<MediaType> mediaTypes = MediaType.parseMediaTypes(acceptHeader);
MediaType.sortByQualityValue(mediaTypes);
if (logger.isDebugEnabled()) {
logger.debug("Requested media types are " + mediaTypes + " (based on Accept header)");
}
return mediaTypes;
}
}
if (this.defaultContentType != null) {
if (logger.isDebugEnabled()) {
logger.debug("Requested media types is " + this.defaultContentType +
" (based on defaultContentType property)");
}
return Collections.singletonList(this.defaultContentType);
}
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 classpath, 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 = this.mediaTypes.get(extension);
if (mediaType == null && this.useJaf && jafPresent) {
mediaType = ActivationMediaTypeFactory.getMediaType(filename);
if (mediaType != null) {
this.mediaTypes.putIfAbsent(extension, mediaType);
}
}
return mediaType;
}
/**
* Determines the {@link MediaType} for the given parameter value.
* <p>The default implementation will check the {@linkplain #setMediaTypes(Map) media types}
* property for a defined mapping.
* <p>This method can be overriden to provide a different algorithm.
* @param parameterValue the parameter value (i.e. {@code pdf}).
* @return the media type, if any
*/
protected MediaType getMediaTypeFromParameter(String parameterValue) {
return this.mediaTypes.get(parameterValue.toLowerCase(Locale.ENGLISH));
}
public View resolveViewName(String viewName, Locale locale) throws Exception {
RequestAttributes attrs = RequestContextHolder.getRequestAttributes();
Assert.isInstanceOf(ServletRequestAttributes.class, attrs);
List<MediaType> requestedMediaTypes = getMediaTypes(((ServletRequestAttributes) attrs).getRequest());
List<View> candidateViews = getCandidateViews(viewName, locale, requestedMediaTypes);
View bestView = getBestView(candidateViews, requestedMediaTypes);
if (bestView != null) {
return bestView;
}
else {
if (this.useNotAcceptableStatusCode) {
if (logger.isDebugEnabled()) {
logger.debug("No acceptable view found; returning 406 (Not Acceptable) status code");
}
return NOT_ACCEPTABLE_VIEW;
}
else {
if (logger.isDebugEnabled()) {
logger.debug("No acceptable view found; returning null");
}
return null;
}
}
}
private List<View> getCandidateViews(String viewName, Locale locale, List<MediaType> requestedMediaTypes)
throws Exception {
List<View> candidateViews = new ArrayList<View>();
for (ViewResolver viewResolver : this.viewResolvers) {
View view = viewResolver.resolveViewName(viewName, locale);
if (view != null) {
candidateViews.add(view);
}
for (MediaType requestedMediaType : requestedMediaTypes) {
List<String> extensions = getExtensionsForMediaType(requestedMediaType);
for (String extension : extensions) {
String viewNameWithExtension = viewName + "." + extension;
view = viewResolver.resolveViewName(viewNameWithExtension, locale);
if (view != null) {
candidateViews.add(view);
}
}
}
}
if (!CollectionUtils.isEmpty(this.defaultViews)) {
candidateViews.addAll(this.defaultViews);
}
return candidateViews;
}
private List<String> getExtensionsForMediaType(MediaType requestedMediaType) {
List<String> result = new ArrayList<String>();
for (Entry<String, MediaType> entry : mediaTypes.entrySet()) {
if (requestedMediaType.includes(entry.getValue())) {
result.add(entry.getKey());
}
}
return result;
}
private View getBestView(List<View> candidateViews, List<MediaType> requestedMediaTypes) {
MediaType bestRequestedMediaType = null;
View bestView = null;
for (MediaType requestedMediaType : requestedMediaTypes) {
for (View candidateView : candidateViews) {
if (StringUtils.hasText(candidateView.getContentType())) {
MediaType candidateContentType = MediaType.parseMediaType(candidateView.getContentType());
if (requestedMediaType.includes(candidateContentType)) {
bestRequestedMediaType = requestedMediaType;
bestView = candidateView;
break;
}
}
}
if (bestView != null) {
if (logger.isDebugEnabled()) {
logger.debug(
"Returning [" + bestView + "] based on requested media type '" + bestRequestedMediaType +
"'");
}
break;
}
}
return bestView;
}
/**
* 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()) {
if (logger.isTraceEnabled()) {
logger.trace("Loading Java Activation Framework FileTypeMap from " + mappingLocation);
}
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
}
}
}
}
if (logger.isTraceEnabled()) {
logger.trace("Loading default Java Activation Framework FileTypeMap");
}
return FileTypeMap.getDefaultFileTypeMap();
}
public static MediaType getMediaType(String fileName) {
String mediaType = fileTypeMap.getContentType(fileName);
return StringUtils.hasText(mediaType) ? MediaType.parseMediaType(mediaType) : null;
}
}
private static final View NOT_ACCEPTABLE_VIEW = new View() {
public String getContentType() {
return null;
}
public void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response)
throws Exception {
response.setStatus(HttpServletResponse.SC_NOT_ACCEPTABLE);
}
};
}
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