Custom JSP tags. This taglib supports dynamic cache. You can cache a whole page or an any part (parts) of it. Also this taglib lets you simulate OutputCache directive in ASP.NET.

Let us see this example:
 

here calculation's results (HTML code) will be saved in the cache for 60 seconds. So for the each next request during that time client will get data directly from the cache (without the new evaluation for tag's body).

Cached data may be persistent (this option should be described by the parameter store). Store is just some existing directory on your server. Saved cache could be restored (e.g. after crashes).

Each data chunk must have own unique key. Under this key you may have more than one cache each of them will be described by request's parameters and/or headers. For doing this you can provide a list of parameters (semicolon separated) and/or a list of headers. E.g.:
 

varyByParam parameter provides a semicolon-separated list of strings used to vary the output cache. By default, these strings correspond to a query string value sent with GET method attributes, or a parameter sent using the POST method. It is similar to an appropriate parameter in ASP.NET OutputCache directive. When this attribute is set to multiple parameters, the output cache contains a different version of the requested body for each specified parameter.
varyByHeader parameter does the same with HTTP headers.

Note for ASP.NET users. To simulate VaryByCustom parameter you may use an expression in a key parameter. This expression could be for example a call to some function that calculates cache key by your own algorithm.

Cache data are separated by the scope. You may cache data per sessions (actually it means caching per users) or per applications (actually it means caching for all users).

Parameter refresh describes how long data will be saved in cache. Another way to describe cache policy is to set some file name. In this case cache validation depends on modification time for this file. Body will be re-evaluated is last modification time has been changed. This option could be useful if tag's body actually depends on this file (e.g. some xsl sheet etc.):
 

Tag forEachKey lets you iterate over existing cache keys. E.g.:
 

Tags are:

Cache

This tag puts own body into cache or outputs cached data. Parameters are:

1) key data key (identification)
2) refresh cache refresh time (in seconds). Default value is 600 (if you did not set depends parameter).
3) depends file name cache depends on
4) scope Data scope. Possible values are: session, application. Default value is session
5) store Optional parameter. Any existing directory on your server. By default data are not persistent.
6) varyByParam Optional parameter. Provides a semicolon-separated list of request parameters. By default is empty.
7) varyByHeader Optional parameter. Provides a semicolon-separated list of request headers. By default is empty.
8) varyByCookie Optional parameter. Provides a semicolon-separated list of cookies. By default is empty.
9) print Optional parameter. Possible values are true or false. If this value is true cached data will be printed, otherwise tag just saves/updates cache. Default value is true.
10) updateCache Optional parameter. Possible values are true or false. If this value is true body will be executed and cached data will be updated regardless of the expiration. Default value is false.
11) noCache Optional parameter. Possible values are true or false. If this value is true body will be executed and all cache related settings will be just ignored. During this execution tag does not change the state of your cache. Default value is false.
12) cacheEmptyBody Optional parameter. Possible values are true or false. If this value is false tag does not cache empty bodies (strings). Default value is true (tag caches all the bodies).

clearCache

Clears cache for the given key (and all subcaches). Parameters are:

1) key data key (identification). You can omit this parameter if you are using this tag inside of forEachKey tag.
2) scope Data scope. Possible values are: session, application. Default value is session
3) cond Optional attribute tag's action depends on. Possible values are true or false. Default value is true (clear cache)

getCache

Prints cached data or puts them into page scope variable. If you set the parameter id data will be saved in the page scope variable described by this parameter. Otherwise tag just prints cached data. Parameters are:

1) key data key (identification). You can omit this parameter if you are using this tag inside of forEachKey tag.
2) scope Data scope. Possible values are: session, application. Default value is session
3) id page scope variable.
4) varyByParam Optional parameter. Provides a semicolon-separated list of request parameters. By default is empty.
5) varyByHeader Optional parameter. Provides a semicolon-separated list of request headers. By default is empty.
6) varyByCookie Optional parameter. Provides a semicolon-separated list of cookies. By default is empty.

restoreCache

Prints cached data from the given store or puts them into page scope variable. If you set the parameter id data will be saved in the page scope variable described by this parameter. Otherwise tag just prints cached data. Parameters are:

1) key data key (identification).
2) scope Data scope. Possible values are: session, application. Default value is session
3) store Describes your store (directory). See Cache tag.
4) id Optional parameter. Descibes a name for the page scope variable.
5) varyByParam Optional parameter. Provides a semicolon-separated list of request parameters. By default is empty.
6) varyByHeader Optional parameter. Provides a semicolon-separated list of request headers. By default is empty.
7) varyByCookie Optional parameter. Provides a semicolon-separated list of cookies. By default is empty.
8) cond Optional attribute tag's action depends on. Possible values are true or false. Default value is true (restore cache)

getHits

Prints a counter for cache hits or saves it in the page scope variable. If you set the parameter id data will be saved in the page scope variable described by this parameter. Otherwise tag just prints data. Parameters are:

1) key data key (identification). You can omit this parameter if you are using this tag inside of forEachKey tag.
2) scope Data scope. Possible values are: session, application. Default value is session
3) id Optional parameter. Describes a name for the page scope variable (type is java.lang.Long) for data. Without this parameter tag just prints data.
4) varyByParam Optional parameter. Provides a semicolon-separated list of request parameters. By default is empty.
5) varyByHeader Optional parameter. Provides a semicolon-separated list of request headers. By default is empty.
6) varyByCookie Optional parameter. Provides a semicolon-separated list of cookies. By default is empty.

getExecutions

Prints a counter for cached data updates (body execution) or saves it in the page scope variable. If you set the parameter id data will be saved in the page scope variable described by this parameter. Otherwise tag just prints data. Parameters are:

1) key data key (identification). You can omit this parameter if you are using this tag inside of forEachKey tag.
2) scope Data scope. Possible values are: session, application. Default value is session
3) id Optional parameter. Describes a name for the page scope variable (type is java.lang.Long) for data. Without this parameter tag just prints data.
4) varyByParam Optional parameter. Provides a semicolon-separated list of request parameters. By default is empty.
5) varyByHeader Optional parameter. Provides a semicolon-separated list of request headers. By default is empty.
6) varyByCookie Optional parameter. Provides a semicolon-separated list of cookies. By default is empty.

getLastModified

Calculates a 'last modified' time for the given cache. If you set the parameter id data will be saved in the page scope variable described by this parameter (type is java.util.Date). Otherwise tag just prints data. Parameters are:

1) key data key (identification). You can omit this parameter if you are using this tag inside of forEachKey tag.
2) scope Data scope. Possible values are: session, application. Default value is session
3) id Optional parameter. Describes a page scope variable (type is java.util.Date) for data. Without this parameter tag just prints data.
4) varyByParam Optional parameter. Provides a semicolon-separated list of request parameters. By default is empty.
5) varyByHeader Optional parameter. Provides a semicolon-separated list of request headers. By default is empty.
6) varyByCookie Optional parameter. Provides a semicolon-separated list of cookies. By default is empty.

ifCached

Body tag. Executes own body in case of described cached data are detected. Parameters are:

1) key data key (identification)
2) scope Data scope. Possible values are: session, application. Default value is session
3) varyByParam Optional parameter. Provides a semicolon-separated list of request parameters. By default is empty.
4) varyByHeader Optional parameter. Provides a semicolon-separated list of request headers. By default is empty.
5) varyByCookie Optional parameter. Provides a semicolon-separated list of cookies. By default is empty.

ifNotCached

Body tag. Executes own body in case of described cache does not exist. Parameters are:

1) key data key (identification)
2) scope Data scope. Possible values are: session, application. Default value is session
3) varyByParam Optional parameter. Provides a semicolon-separated list of request parameters. By default is empty.
4) varyByHeader Optional parameter. Provides a semicolon-separated list of request headers. By default is empty.
5) varyByCookie Optional parameter. Provides a semicolon-separated list of cookies. By default is empty.

forEachKey

Body tag lets you iterate over existing cache keys. Tag executes own body for the each key in the given scope. Parameters are:

1) id Optional parameter. Describes a name for the page scope varible (type is java.lang.String) you can use as a reference to the current key. Default value is cacheKey.
2) scope Optional parameter. Describes a data scope. Possible values are: session, application. Default value is session

for downloading:

Library: cachetag.jar    Description: taglib.tld

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 See also Coldtags suite - the largest collection of custom JSP tags.

• Cache filter
• Cached response