org.springframework.web.servlet.view
Class AbstractCachingViewResolver

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

All Implemented Interfaces:

ApplicationContextAware, ViewResolver

Direct Known Subclasses:

ResourceBundleViewResolver, UrlBasedViewResolver, XmlViewResolver

public abstract class AbstractCachingViewResolver
extends WebApplicationObjectSupport
implements ViewResolver

Convenient superclass for view resolvers. Caches views once resolved: This means that view resolution won't be a performance problem, no matter how costly initial view retrieval is.

View retrieval is deferred to subclasses via the loadView template method.

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 String	getCacheKey(String viewName, Locale locale) Return the cache key for the given viewName and the given locale.
boolean	isCache() Return if caching is enabled.
protected abstract View	loadView(String viewName, Locale locale) Subclasses must implement this method.
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, isContextRequired

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. Disable this only for debugging and development. Default is for caching to be enabled.

Warning: Disabling caching can severely impact performance. Tests indicate that turning caching off reduces performance by at least 20%. Increased object churn probably eventually makes the problem even worse.

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 String getCacheKey(String viewName,
                             Locale locale)

Return the cache key for the given viewName and the given locale. Needs to regard the locale in general, as a different locale can lead to a different view! Can be overridden in subclasses.

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. Default implementation delegates to loadView.

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. There need be no concern for efficiency, as this class will cache views.

Not all subclasses may support internationalization: A subclass that doesn't can simply ignore the locale parameter.

NOTE: As of Spring 1.2, subclasses are supposed to fully initialize the View objects before returning them, also applying bean container initialization callbacks.

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)