com.sun.appserv.web.taglibs.cache

Class CacheTag

java.lang.Object

javax.servlet.jsp.tagext.TagSupport

javax.servlet.jsp.tagext.BodyTagSupport

com.sun.appserv.web.taglibs.cache.CacheTag

All Implemented Interfaces:

Serializable, javax.servlet.jsp.tagext.BodyTag, javax.servlet.jsp.tagext.IterationTag, javax.servlet.jsp.tagext.JspTag, javax.servlet.jsp.tagext.Tag

public class CacheTag
extends javax.servlet.jsp.tagext.BodyTagSupport

CacheTag is a JSP tag that allows server-side caching of JSP page fragments. It lets you specify a timeout for how long the cached data is valid. It also gives you programmatic control over key generation, refreshing of the cache and whether the cached content should be served or not. Usage Example: <%@ taglib prefix="ias" uri="Sun ONE Application Server Tags" %> ... expensive operation ...

See Also:

Serialized Form

Field Summary

Fields inherited from class javax.servlet.jsp.tagext.BodyTagSupport

bodyContent

Fields inherited from class javax.servlet.jsp.tagext.TagSupport

id, pageContext

Fields inherited from interface javax.servlet.jsp.tagext.BodyTag

EVAL_BODY_BUFFERED, EVAL_BODY_TAG

Fields inherited from interface javax.servlet.jsp.tagext.IterationTag

EVAL_BODY_AGAIN

Fields inherited from interface javax.servlet.jsp.tagext.Tag

EVAL_BODY_INCLUDE, EVAL_PAGE, SKIP_BODY, SKIP_PAGE

Constructor Summary

Constructors

Constructor and Description
CacheTag()

Method Summary

Modifier and Type	Method and Description
int	doAfterBody() doAfterBody is called only if the body was evaluated.
int	doEndTag() doEndTag just resets all the valiables in case the tag is reused
int	doStartTag() doStartTag is called every time the cache tag is encountered.
void	setKey(String key) This is used to set a user-defined key to store the response in the cache.
void	setNocache(boolean noCache) This attribute is used to programmatically enable or disable the use of the cached response.
void	setRefresh(boolean refresh) This attribute is used to programmatically refresh the cached response.
void	setScope(String scope) Sets the scope of the cache.
void	setTimeout(String timeout) This sets the time for which the cached response is valid.

Methods inherited from class javax.servlet.jsp.tagext.BodyTagSupport

doInitBody, getBodyContent, getPreviousOut, release, setBodyContent

Methods inherited from class javax.servlet.jsp.tagext.TagSupport

findAncestorWithClass, getId, getParent, getValue, getValues, removeValue, setId, setPageContext, setParent, setValue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface javax.servlet.jsp.tagext.Tag

getParent, setPageContext, setParent

Constructor Detail

CacheTag

public CacheTag()

Method Detail

doStartTag

public int doStartTag()
               throws javax.servlet.jsp.JspException

doStartTag is called every time the cache tag is encountered. By the time this is called, the tag attributes are already set, but the tag body has not been evaluated. The cache key is generated here and the cache is obtained as well

Specified by:

doStartTag in interface javax.servlet.jsp.tagext.Tag

Overrides:

doStartTag in class javax.servlet.jsp.tagext.BodyTagSupport

Returns:

EVAL_BODY_INCLUDE when nocache is specified so that the tag body is just evaluated into the output stream SKIP_BODY if the cached response is valid in which case it is just written to the output stream, hence there is nothing more to be done. EVAL_BODY_BUFFERED is the default return value which ensures that the BodyContent is created and the tag body is evaluated into it.

Throws:

javax.servlet.jsp.JspException - the standard exception thrown

doAfterBody

public int doAfterBody()
                throws javax.servlet.jsp.JspException

doAfterBody is called only if the body was evaluated. This would happen if nocache is specified in which case this should do nothing if there was no cached response in which case the response data is obtained from the bodyContent and cached if the response has expired in which case the cache is refreshed

Specified by:

doAfterBody in interface javax.servlet.jsp.tagext.IterationTag

Overrides:

doAfterBody in class javax.servlet.jsp.tagext.BodyTagSupport

Returns:

always returns SKIP_BODY since we dont do any iteration

Throws:

javax.servlet.jsp.JspException - the standard exception thrown

doEndTag

public int doEndTag()
             throws javax.servlet.jsp.JspException

doEndTag just resets all the valiables in case the tag is reused

Specified by:

doEndTag in interface javax.servlet.jsp.tagext.Tag

Overrides:

doEndTag in class javax.servlet.jsp.tagext.BodyTagSupport

Returns:

always returns EVAL_PAGE since we want the entire jsp evaluated

Throws:

javax.servlet.jsp.JspException - the standard exception thrown

setKey

public void setKey(String key)

This is used to set a user-defined key to store the response in the cache.

setTimeout

public void setTimeout(String timeout)

This sets the time for which the cached response is valid. The cached entry is invalid after this time is past. If no unit is specified, then the timeout is assumed to be in seconds. A different unit can be specified by postfixing the timeout value with the desired unit: s=seconds, m=minutes, h=hours, d=days

setNocache

public void setNocache(boolean noCache)

This attribute is used to programmatically enable or disable the use of the cached response. If noCache is true, then the cached response is not sent, instead the tag body is evaluated and sent out, the cache is not refreshed either.

setRefresh

public void setRefresh(boolean refresh)

This attribute is used to programmatically refresh the cached response. If refresh is true, the cached response is not sent, instead the tag body is evaluated and sent and the cache is refreshed with the new response.

setScope

public void setScope(String scope)

Sets the scope of the cache.

Parameters:

scope - the scope of the cache

Throws:

IllegalArgumentException - if the specified scope is different from request, session, and application