org.springframework.web.servlet.view
Class AbstractCachingViewResolver

java.lang.Object
  extended by org.springframework.context.support.ApplicationObjectSupport
      extended by org.springframework.web.context.support.WebApplicationObjectSupport
          extended by org.springframework.web.servlet.view.AbstractCachingViewResolver
All Implemented Interfaces:
Aware, ApplicationContextAware, ServletContextAware, ViewResolver
Direct Known Subclasses:
ResourceBundleViewResolver, UrlBasedViewResolver, XmlViewResolver

public abstract class AbstractCachingViewResolver
extends WebApplicationObjectSupport
implements ViewResolver

Convenient base class for ViewResolver implementations. Caches View objects once resolved: This means that view resolution won't be a performance problem, no matter how costly initial view retrieval is.

Subclasses need to implement the loadView(java.lang.String, java.util.Locale) template method, building the View object for a specific view name and locale.

Author:
Rod Johnson, Juergen Hoeller
See Also:
loadView(java.lang.String, java.util.Locale)

Field Summary
 
Fields inherited from class org.springframework.context.support.ApplicationObjectSupport
logger
 
Constructor Summary
AbstractCachingViewResolver()
           
 
Method Summary
 void clearCache()
          Clear the entire view cache, removing all cached view objects.
protected  View createView(String viewName, Locale locale)
          Create the actual View object.
protected  Object getCacheKey(String viewName, Locale locale)
          Return the cache key for the given view name and the given locale.
 boolean isCache()
          Return if caching is enabled.
protected abstract  View loadView(String viewName, Locale locale)
          Subclasses must implement this method, building a View object for the specified view.
 void removeFromCache(String viewName, Locale locale)
          Provides functionality to clear the cache for a certain view.
 View resolveViewName(String viewName, Locale locale)
          Resolve the given view by name.
 void setCache(boolean cache)
          Enable or disable caching.
 
Methods inherited from class org.springframework.web.context.support.WebApplicationObjectSupport
getServletContext, getTempDir, getWebApplicationContext, initApplicationContext, initServletContext, 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

AbstractCachingViewResolver

public AbstractCachingViewResolver()
Method Detail

setCache

public void setCache(boolean cache)
Enable or disable caching.

Default is "true": caching is enabled. Disable this only for debugging and development.

Warning: Disabling caching can severely impact performance.


isCache

public boolean isCache()
Return if caching is enabled.


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)

getCacheKey

protected Object getCacheKey(String viewName,
                             Locale locale)
Return the cache key for the given view name and the given locale.

Default is a String consisting of view name and locale suffix. Can be overridden in subclasses.

Needs to respect the locale in general, as a different locale can lead to a different view resource.


removeFromCache

public void removeFromCache(String viewName,
                            Locale locale)
Provides functionality to clear the cache for a certain view.

This can be handy in case developer are able to modify views (e.g. Velocity templates) at runtime after which you'd need to clear the cache for the specified view.

Parameters:
viewName - the view name for which the cached view object (if any) needs to be removed
locale - the locale for which the view object should be removed

clearCache

public void clearCache()
Clear the entire view cache, removing all cached view objects. Subsequent resolve calls will lead to recreation of demanded view objects.


createView

protected View createView(String viewName,
                          Locale locale)
                   throws Exception
Create the actual View object.

The default implementation delegates to loadView(java.lang.String, java.util.Locale). This can be overridden to resolve certain view names in a special fashion, before delegating to the actual loadView implementation provided by the subclass.

Parameters:
viewName - the name of the view to retrieve
locale - the Locale to retrieve the view for
Returns:
the View instance, or null if not found (optional, to allow for ViewResolver chaining)
Throws:
Exception - if the view couldn't be resolved
See Also:
loadView(java.lang.String, java.util.Locale)

loadView

protected abstract View loadView(String viewName,
                                 Locale locale)
                          throws Exception
Subclasses must implement this method, building a View object for the specified view. The returned View objects will be cached by this ViewResolver base class.

Subclasses are not forced to support internationalization: A subclass that does not may simply ignore the locale parameter.

Parameters:
viewName - the name of the view to retrieve
locale - the Locale to retrieve the view for
Returns:
the View instance, or null if not found (optional, to allow for ViewResolver chaining)
Throws:
Exception - if the view couldn't be resolved
See Also:
resolveViewName(java.lang.String, java.util.Locale)