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:

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

Modifier and Type	Field and Description
static int	DEFAULT_CACHE_LIMIT Default maximum number of entries for the view cache: 1024

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

logger

Constructor Summary

Constructors

Constructor and Description
AbstractCachingViewResolver()

Method Summary

Modifier and Type	Method and Description
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.
int	getCacheLimit() Return the maximum number of entries for the view cache.
boolean	isCache() Return if caching is enabled.
boolean	isCacheUnresolved() Return if caching of unresolved views 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.
void	setCacheLimit(int cacheLimit) Specify the maximum number of entries for the view cache.
void	setCacheUnresolved(boolean cacheUnresolved) Whether a view name once resolved to null should be cached and automatically resolved to null subsequently.

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

Field Detail

DEFAULT_CACHE_LIMIT

public static final int DEFAULT_CACHE_LIMIT

Default maximum number of entries for the view cache: 1024

See Also:

Constant Field Values

Constructor Detail

AbstractCachingViewResolver

public AbstractCachingViewResolver()

Method Detail

setCacheLimit

public void setCacheLimit(int cacheLimit)

Specify the maximum number of entries for the view cache. Default is 1024.

getCacheLimit

public int getCacheLimit()

Return the maximum number of entries for the view cache.

setCache

public void setCache(boolean cache)

Enable or disable caching.

This is equivalent to setting the "cacheLimit" property to the default limit (1024) or to 0, respectively.

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

isCache

public boolean isCache()

Return if caching is enabled.

setCacheUnresolved

public void setCacheUnresolved(boolean cacheUnresolved)

Whether a view name once resolved to null should be cached and automatically resolved to null subsequently.

Default is "true": unresolved view names are being cached, as of Spring 3.1. Note that this flag only applies if the general "cache" flag is kept at its default of "true" as well.

Of specific interest is the ability for some AbstractUrlBasedView implementations (FreeMarker, Velocity, Tiles) to check if an underlying resource exists via AbstractUrlBasedView.checkResource(Locale). With this flag set to "false", an underlying resource that re-appears is noticed and used. With the flag set to "true", one check is made only.

isCacheUnresolved

public boolean isCacheUnresolved()

Return if caching of unresolved views 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)