org.springframework.web.servlet.view
Class AbstractCachingViewResolver

java.lang.Object
  extended byorg.springframework.context.support.ApplicationObjectSupport
      extended byorg.springframework.web.context.support.WebApplicationObjectSupport
          extended byorg.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
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)

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

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.


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.

This method is not supposed to fully initialize the view (for example, ApplicationContextAware methods haven't been called yet). Clients should only be using resolveViewName, which does fully initialize the view objects found.

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)


Copyright (C) 2003-2004 The Spring Framework Project.