org.springframework.web.servlet.view
Class ContentNegotiatingViewResolver

java.lang.Object
  org.springframework.context.support.ApplicationObjectSupport
      org.springframework.web.context.support.WebApplicationObjectSupport
          org.springframework.web.servlet.view.ContentNegotiatingViewResolver

All Implemented Interfaces:

ApplicationContextAware, Ordered, ServletContextAware, ViewResolver

public class ContentNegotiatingViewResolver
extends WebApplicationObjectSupport
implements ViewResolver, Ordered

Implementation of ViewResolver that resolves a view based on the request file name or Accept header.

The ContentNegotiatingViewResolver does not resolve views itself, but delegates to other ViewResolvers. By default, these other view resolvers are picked up automatically from the application context, though they can also be set explicitly by using the viewResolvers property. Note that in order for this view resolver to work properly, the order property needs to be set to a higher precedence than the others (the default is Ordered.HIGHEST_PRECEDENCE.)

This view resolver uses the requested media type to select a suitable View for a request. This media type is determined by using the following criteria:

1. If the requested path has a file extension and if the setFavorPathExtension(boolean) property is true, the mediaTypes property is inspected for a matching media type.
2. If the request contains a parameter defining the extension and if the setFavorParameter(boolean) property is true, the mediaTypes property is inspected for a matching media type. The default name of the parameter is format and it can be configured using the parameterName property.
3. If there is no match in the mediaTypes property and if the Java Activation Framework (JAF) is present on the class path, FileTypeMap.getContentType(String) is used instead.
4. If the previous steps did not result in a media type, and ignoreAcceptHeader is false, the request Accept header is used.

Once the requested media type has been determined, this resolver queries each delegate view resolver for a View and determines if the requested media type is compatible with the view's content type). The most compatible view is returned.

Additionally, this view resolver exposes the 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 Accept header, described above). You can also set the default content type directly, which will be returned when the other mechanisms (Accept header, file extension or parameter) do not result in a match.

For example, if the request path is /view.html, this view resolver will look for a view that has the text/html content type (based on the html file extension). A request for /view with a text/html request Accept header has the same result.

Since:

3.0

Author:

Arjen Poutsma, Juergen Hoeller

See Also:

ViewResolver, InternalResourceViewResolver, BeanNameViewResolver

Field Summary

Fields inherited from class org.springframework.context.support.ApplicationObjectSupport

logger

Fields inherited from interface org.springframework.core.Ordered

HIGHEST_PRECEDENCE, LOWEST_PRECEDENCE

Constructor Summary

ContentNegotiatingViewResolver()

Method Summary

protected MediaType	getMediaTypeFromFilename(String filename) Determines the MediaType for the given filename.
protected MediaType	getMediaTypeFromParameter(String parameterValue) Determines the MediaType for the given parameter value.
protected List<MediaType>	getMediaTypes(HttpServletRequest request) Determines the list of MediaType for the given HttpServletRequest.
int	getOrder() Return the order value of this object, with a higher value meaning greater in terms of sorting.
protected void	initServletContext(ServletContext servletContext) Subclasses may override this for custom initialization based on the ServletContext that this application object runs in.
View	resolveViewName(String viewName, Locale locale) Resolve the given view by name.
void	setDefaultContentType(MediaType defaultContentType) Sets the default content type.
void	setDefaultViews(List<View> defaultViews) Sets the default views to use when a more specific view can not be obtained from the ViewResolver chain.
void	setFavorParameter(boolean favorParameter) Indicates whether a request parameter should be used to determine the requested media type, in favor of looking at the Accept header.
void	setFavorPathExtension(boolean favorPathExtension) Indicates whether the extension of the request path should be used to determine the requested media type, in favor of looking at the Accept header.
void	setIgnoreAcceptHeader(boolean ignoreAcceptHeader) Indicates whether the HTTP Accept header should be ignored.
void	setMediaTypes(Map<String,String> mediaTypes) Sets the mapping from file extensions to media types.
void	setOrder(int order)
void	setParameterName(String parameterName) Sets the parameter name that can be used to determine the requested media type if the setFavorParameter(boolean) property is true.
void	setViewResolvers(List<ViewResolver> viewResolvers) Sets the view resolvers to be wrapped by this view resolver.

Methods inherited from class org.springframework.web.context.support.WebApplicationObjectSupport

getServletContext, getTempDir, getWebApplicationContext, initApplicationContext, isContextRequired, setServletContext

Methods inherited from class org.springframework.context.support.ApplicationObjectSupport

getApplicationContext, getMessageSourceAccessor, initApplicationContext, requiredContextClass, setApplicationContext

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ContentNegotiatingViewResolver

public ContentNegotiatingViewResolver()

Method Detail

setOrder

public void setOrder(int order)

getOrder

public int getOrder()

Description copied from interface: Ordered

Return the order value of this object, with a higher value meaning greater in terms of sorting.

Normally starting with 0, with Integer.MAX_VALUE indicating the greatest value. Same order values will result in arbitrary positions for the affected objects.

Higher values can be interpreted as lower priority. As a consequence, the object with the lowest value has highest priority (somewhat analogous to Servlet "load-on-startup" values).

Specified by:

getOrder in interface Ordered

Returns:

the order value

setFavorPathExtension

public void setFavorPathExtension(boolean favorPathExtension)

Indicates whether the extension of the request path should be used to determine the requested media type, in favor of looking at the Accept header. The default value is true.

For instance, when this flag is true (the default), a request for /hotels.pdf will result in an AbstractPdfView being resolved, while the Accept header can be the browser-defined text/html,application/xhtml+xml.

setFavorParameter

public void setFavorParameter(boolean favorParameter)

Indicates whether a request parameter should be used to determine the requested media type, in favor of looking at the Accept header. The default value is false.

For instance, when this flag is true, a request for /hotels?format=pdf will result in an AbstractPdfView being resolved, while the Accept header can be the browser-defined text/html,application/xhtml+xml.

setParameterName

public void setParameterName(String parameterName)

Sets the parameter name that can be used to determine the requested media type if the setFavorParameter(boolean) property is true. The default parameter name is format.

setIgnoreAcceptHeader

public void setIgnoreAcceptHeader(boolean ignoreAcceptHeader)

Indicates whether the HTTP Accept header should be ignored. Default is false. If set to true, this view resolver will only refer to the file extension and/or paramter, as indicated by the favorPathExtension and favorParameter properties.

setMediaTypes

public void setMediaTypes(Map<String,String> mediaTypes)

Sets the mapping from file extensions to media types.

When this mapping is not set or when an extension is not present, this view resolver will fall back to using a FileTypeMap when the Java Action Framework is available.

setDefaultViews

public void setDefaultViews(List<View> defaultViews)

Sets the default views to use when a more specific view can not be obtained from the ViewResolver chain.

setDefaultContentType

public void setDefaultContentType(MediaType defaultContentType)

Sets the default content type.

This content type will be used when file extension, parameter, nor Accept header define a content-type, either through being disabled or empty.

setViewResolvers

public void setViewResolvers(List<ViewResolver> viewResolvers)

Sets the view resolvers to be wrapped by this view resolver.

If this property is not set, view resolvers will be detected automatically.

initServletContext

protected void initServletContext(ServletContext servletContext)

Description copied from class: WebApplicationObjectSupport

Subclasses may override this for custom initialization based on the ServletContext that this application object runs in.

The default implementation is empty. Called by WebApplicationObjectSupport.initApplicationContext(org.springframework.context.ApplicationContext) as well as WebApplicationObjectSupport.setServletContext(javax.servlet.ServletContext).

Overrides:

initServletContext in class WebApplicationObjectSupport

Parameters:

servletContext - the ServletContext that this application object runs in (never null)

getMediaTypes

protected List<MediaType> getMediaTypes(HttpServletRequest request)

Determines the list of MediaType for the given HttpServletRequest.

The default implementation invokes getMediaTypeFromFilename(String) if favorPathExtension property is true. If the property is false, or when a media type cannot be determined from the request path, this method will inspect the Accept header of the request.

This method can be overriden to provide a different algorithm.

Parameters:

request - the current servlet request

Returns:

the list of media types requested, if any

getMediaTypeFromFilename

protected MediaType getMediaTypeFromFilename(String filename)

Determines the MediaType for the given filename.

The default implementation will check the 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 FileTypeMap.getContentType(String)

This method can be overriden to provide a different algorithm.

Parameters:

filename - the current request file name (i.e. hotels.html)

Returns:

the media type, if any

getMediaTypeFromParameter

protected MediaType getMediaTypeFromParameter(String parameterValue)

Determines the MediaType for the given parameter value.

The default implementation will check the media types property for a defined mapping.

This method can be overriden to provide a different algorithm.

Parameters:

parameterValue - the parameter value (i.e. pdf).

Returns:

the media type, if any

resolveViewName

public View resolveViewName(String viewName,
                            Locale locale)
                     throws Exception

Description copied from interface: ViewResolver

Resolve the given view by name.

Note: To allow for ViewResolver chaining, a ViewResolver should return null if a view with the given name is not defined in it. However, this is not required: Some ViewResolvers will always attempt to build View objects with the given name, unable to return null (rather throwing an exception when View creation failed).

Specified by:

resolveViewName in interface ViewResolver

Parameters:

viewName - name of the view to resolve

locale - Locale in which to resolve the view. ViewResolvers that support internationalization should respect this.

Returns:

the View object, or null if not found (optional, to allow for ViewResolver chaining)

Throws:

Exception - if the view cannot be resolved (typically in case of problems creating an actual View object)