Sun Java System Web Server 7.0 Developer's Guide to Java Web Applications

CacheHelper Interface

The CacheHelper interface includes the following information:

package com.sun.appserv.web.cache;
import java.util.Map
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
/** CacheHelper interface is an user-extensible interface to customize:
 * a) the key generation b) whether to cache the response.
public interface CacheHelper {
// name of request attributes
   public static final String ATTR_CACHE_MAPPED_SERVLET_NAME =
   public static final String ATTR_CACHE_MAPPED_URL_PATTERN =
public static final int TIMEOUT_VALUE_NOT_SET = -2;
/** initialize the helper
    * @param context the web application context this helper belongs to
    * @exception Exception if a startup error occurs
   public void init(ServletContext context, Map props) throws Exception;
/** getCacheKey: generate the key to be used to cache this request
    * @param request incoming <code>HttpServletRequest</code> object
    * @returns the generated key for this requested cacheable resource.
   public String getCacheKey(HttpServletRequest request);
/** isCacheable: is the response to given request cacheable?
    * @param request incoming <code>HttpServletRequest</code> object
    * @returns <code>true</code> if the response could be cached. or
    * <code>false</code> if the results of this request must not be cached.
   public boolean isCacheable(HttpServletRequest request);
/** isRefreshNeeded: is the response to given request to be refreshed?
    * @param request incoming <code>HttpServletRequest</code> object
    * @returns <code>true</code> if the response needs to be refreshed.
    * or return <code>false</code> if the results of this request
    * dont need to be refreshed.
   public boolean isRefreshNeeded(HttpServletRequest request);
/** get timeout for the cached response.
    * @param request incoming <code>HttpServletRequest</code> object
    * @returns the timeout in seconds for the cached response; a return
    * value of -1 means the response never expires and a value of -2 indicates
    * helper cannot determine the timeout (container assigns default timeout)
public int getTimeout(HttpServletRequest request);
    * Stop the helper from active use
    * @exception Exception if an error occurs
   public void destroy() throws Exception;