SunONE Application Server v8.0 PE

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

java.lang.Object
  extended byjavax.servlet.jsp.tagext.TagSupport
      extended byjavax.servlet.jsp.tagext.BodyTagSupport
          extended bycom.sun.appserv.web.taglibs.cache.CacheTag
All Implemented Interfaces:
BodyTag, IterationTag, JspTag, java.io.Serializable, Tag

public class CacheTag
extends 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
CacheTag()
          Default constructor that simply gets a handle to the web container subsystem's logger.
 
Method Summary
 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(java.lang.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(java.lang.String scope)
          This attribute is used to set the scope of the cache.
 void setTimeout(java.lang.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()
Default constructor that simply gets a handle to the web container subsystem's logger.

Method Detail

doStartTag

public int doStartTag()
               throws 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 Tag
Overrides:
doStartTag in class 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:
JspException - the standard exception thrown
See Also:
Tag.doStartTag()

doAfterBody

public int doAfterBody()
                throws 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 IterationTag
Overrides:
doAfterBody in class BodyTagSupport
Returns:
always returns SKIP_BODY since we dont do any iteration
Throws:
JspException - the standard exception thrown
See Also:
BodyTagSupport.doInitBody(), IterationTag.doAfterBody()

doEndTag

public int doEndTag()
             throws JspException
doEndTag just resets all the valiables in case the tag is reused

Specified by:
doEndTag in interface Tag
Overrides:
doEndTag in class BodyTagSupport
Returns:
always returns EVAL_PAGE since we want the entire jsp evaluated
Throws:
JspException - the standard exception thrown
See Also:
Tag.doEndTag()

setKey

public void setKey(java.lang.String key)
This is used to set a user-defined key to store the response in the cache.


setTimeout

public void setTimeout(java.lang.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(java.lang.String scope)
This attribute is used to set the scope of the cache. It can be either "session" or "application".


SunONE Application Server v8.0 PE

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