Class \Prado\Web\UI\WebControls\TOutputCache
TOutputCache enables caching a portion of a Web page, also known as partial caching. The content being cached can be either static or dynamic.
To use TOutputCache, simply enclose the content to be cached within the TOutputCache component tag on a template, e.g.,
<com:TOutputCache>
content to be cached
</com:TOutputCache>
where content to be cached can be static text and/or component tags.
The validity of the cached content is determined based on two factors: the \Prado\Web\UI\WebControls\setDuration and the cache dependency. The former specifies the number of seconds that the data can remain valid in cache (defaults to 60s), while the latter specifies conditions that the cached data depends on. If a dependency changes, (e.g. relevant data in DB are updated), the cached data will be invalidated.
There are two ways to specify cache dependency. One may write event handlers to respond to the \Prado\Web\UI\WebControls\onCheckDependency event and set the event parameter's \Prado\Web\UI\WebControls\TOutputCacheCheckDependencyEventParameter::getIsValid property to indicate whether the cached data remains valid or not. One can also extend TOutputCache and override its getCacheDependency function. While the former is easier to use, the latter offers more extensibility.
The content fetched from cache may be variated with respect to some parameters. It supports variation with respect to request parameters, which is specified by \Prado\Web\UI\WebControls\setVaryByParam property. If a specified request parameter is different, a different version of cached content is used. This is extremely useful if a page's content may be variated according to some GET parameters. The content being cached may also be variated with user sessions if \Prado\Web\UI\WebControls\setVaryBySession is set true. To variate the cached content by other factors, override calculateCacheKey() method.
Output caches can be nested. An outer cache takes precedence over an inner cache. This means, if the content cached by the inner cache expires or is invalidated, while that by the outer cache not, the outer cached content will be used.
Note, TOutputCache is effective only for non-postback page requests and when cache module is enabled.
Do not attempt to address child controls of TOutputCache when the cached content is to be used. Use \Prado\Web\UI\WebControls\getContentCached property to determine whether the content is cached or not.
Class hierarchy
- \Prado\Web\UI\WebControls\TOutputCache implements INamingContainer
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\Prado\Web\UI\TControl
implements
IRenderable, IBindable -
\Prado\TApplicationComponent
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\Prado\TComponent
Since: 3.1
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getAllowChildControls() : bool
Returns a value indicating whether body contents are allowed for this control.
This method overrides the parent implementation by checking if cached content is available or not. If yes, it returns false, otherwise true. |
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public
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onCalculateKey(TOutputCacheCalculateKeyEventParameter $param) : mixed
This event is raised when the output cache is calculating cache key.
By varying cache keys, one can obtain different versions of cached content. An event handler may be written to add variety of the key calculation. The value set in \Prado\Web\UI\WebControls\TOutputCacheCalculateKeyEventParameter::setCacheKey of this event parameter will be appended to the default key calculation scheme. |
public
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onCheckDependency(TOutputCacheCheckDependencyEventParameter $param) : mixed
This event is raised when the output cache is checking cache dependency.
An event handler may be written to check customized dependency conditions. The checking result should be saved by setting \Prado\Web\UI\WebControls\TOutputCacheCheckDependencyEventParameter::setIsValid property of the event parameter (which defaults to true). |
public
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registerAction(string $context, string $funcName, array<string|int, mixed> $funcParams) : mixed
Registers an action associated with the content being cached.
The registered action will be replayed if the content stored in the cache is served to end-users. |
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render(THtmlWriter $writer) : mixed
Renders the output cache control.
This method overrides the parent implementation by capturing the output from its child controls and saving it into cache, if output cache is needed. |
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setCacheKeyPrefix(string $value) : mixed
Sets the prefix of the cache key.
This method is used internally by TTemplate. |
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setCachingPostBack(bool $value) : mixed
Sets a value indicating whether cached output will be used on postback requests.
By default, this is disabled. Be very cautious when enabling it. If the cached content including interactive user controls such as TTextBox, TDropDownList, your page may fail to render on postbacks. |
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setVaryByParam(string $value) : mixed
Sets the names of the request parameters that should be used in calculating the cache key.
The names should be concatenated by semicolons. By setting this value, the output cache will use different cached data for each different set of request parameter values. |
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calculateCacheKey() : string
Calculates the cache key.
The key is calculated based on the unique ID of this control and the request parameters specified via \Prado\Web\UI\WebControls\setVaryByParam. If \Prado\Web\UI\WebControls\getVaryBySession is true, the session ID will also participate in the key calculation. This method may be overriden to support other variations in the calculated cache key. |
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getCacheDependency() : ICacheDependency
Returns the dependency of the data to be cached.
The default implementation simply returns null, meaning no specific dependency. This method may be overriden to associate the data to be cached with additional dependencies. |
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initRecursive([TControl $namingContainer = null ]) : mixed
Performs the Init step for the control and all its child controls.
This method overrides the parent implementation by setting up the stack of the output cache in the page. Only framework developers should use this method. |
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loadRecursive() : mixed
Performs the Load step for the control and all its child controls.
This method overrides the parent implementation by setting up the stack of the output cache in the page. If the data is restored from cache, it also recovers the actions associated with the cached data. Only framework developers should use this method. |
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loadStateRecursive(array<string|int, mixed> &$state[, bool $needViewState = true ]) : mixed
Loads state (viewstate and controlstate) into a control and its children.
This method overrides the parent implementation by loading cached state if available. This method should only be used by framework developers. |
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preRenderRecursive() : mixed
Performs the PreRender step for the control and all its child controls.
This method overrides the parent implementation by setting up the stack of the output cache in the page. Only framework developers should use this method. |
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saveStateRecursive([bool $needViewState = true ]) : array<string|int, mixed>
Saves all control state (viewstate and controlstate) as a collection.
This method overrides the parent implementation by saving state into cache if needed. This method should only be used by framework developers. |
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private
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mixed
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CACHE_ID_PREFIX
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'prado:outputcache'
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