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package com.sun.appserv.web.taglibs.cache;
import com.sun.appserv.util.cache.Cache;
import com.sun.appserv.web.cache.CacheManager;
import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
/**
* ServletRequestListener which creates a cache for JSP tag body invocations
* and adds it as a request attribute in response to requestInitialized
* events, and clears the cache in response to requestDestroyed events.
*/
public class CacheRequestListener implements ServletRequestListener {
/**
* No-arg constructor
*/
public CacheRequestListener() {}
/**
* Receives notification that the request is about to enter the scope
* of the web application, and adds newly created cache for JSP tag
* body invocations as a request attribute.
*
* @param sre the notification event
*/
public void requestInitialized(ServletRequestEvent sre) {
ServletContext context = sre.getServletContext();
// Check if a cache manager has already been created and set in the
// context
CacheManager cm = (CacheManager)
context.getAttribute(CacheManager.CACHE_MANAGER_ATTR_NAME);
// Create a new cache manager if one is not present and use it
// to create a new cache
if (cm == null) {
cm = new CacheManager();
}
Cache cache = null;
try {
cache = cm.createCache();
} catch (Exception ex) {}
// Set the cache as a request attribute
if (cache != null) {
ServletRequest req = sre.getServletRequest();
req.setAttribute(Constants.JSPTAG_CACHE_KEY, cache);
}
}
/**
* Receives notification that the request is about to go out of scope
* of the web application, and clears the request's cache of JSP tag
* body invocations (if present).
*
* @param sre the notification event
*/
public void requestDestroyed(ServletRequestEvent sre) {
// Clear the cache
ServletRequest req = sre.getServletRequest();
Cache cache = (Cache) req.getAttribute(Constants.JSPTAG_CACHE_KEY);
if (cache != null) {
cache.clear();
}
}
}