net.sf.ehcache.constructs.web.filter
Class SimplePageCachingFilterWithBlankPageProblem

java.lang.Object
  net.sf.ehcache.constructs.web.filter.Filter
      net.sf.ehcache.constructs.web.filter.CachingFilter
          net.sf.ehcache.constructs.web.filter.SimplePageCachingFilter
              net.sf.ehcache.constructs.web.filter.SimplePageCachingFilterWithBlankPageProblem

All Implemented Interfaces:

javax.servlet.Filter

public class SimplePageCachingFilterWithBlankPageProblem
extends SimplePageCachingFilter

This implementation only writes the response when it is not committed. This is half right. In the wild it can cause the dreaded blank page problem.

Another half right solution is to write the response. The problem then is, if the response is gzipped, the body might be gzipped but the headers won't show it. The result will be yet another blank page in Internet Explorer.

The correct thing to do is to throw an exception.

Version:

$Id: SimplePageCachingFilterWithBlankPageProblem.java 796 2008-10-09 02:39:03Z gregluck $

Author:

Greg Luck

See Also:

SimplePageCachingFilter

Field Summary

static String

NAME The name of the filter.

Fields inherited from class net.sf.ehcache.constructs.web.filter.SimplePageCachingFilter

DEFAULT_CACHE_NAME

Fields inherited from class net.sf.ehcache.constructs.web.filter.CachingFilter

blockingCache, cacheName

Fields inherited from class net.sf.ehcache.constructs.web.filter.Filter

exceptionsToLogDifferently, filterConfig, NO_FILTER, suppressStackTraces

Constructor Summary

SimplePageCachingFilterWithBlankPageProblem()

Method Summary

protected void

doFilter(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, javax.servlet.FilterChain chain) Performs the filtering for a request.

Methods inherited from class net.sf.ehcache.constructs.web.filter.SimplePageCachingFilter

calculateKey, getCacheManager, getCacheName

Methods inherited from class net.sf.ehcache.constructs.web.filter.CachingFilter

buildPage, buildPageInfo, checkNoReentry, doDestroy, doInit, setCacheNameIfAnyConfigured, setContentType, setCookies, setHeaders, setStatus, writeContent, writeResponse

Methods inherited from class net.sf.ehcache.constructs.web.filter.Filter

acceptsEncoding, acceptsGzipEncoding, destroy, doFilter, filterNotDisabled, getFilterConfig, init, logRequestHeaders, processInitParams

Methods inherited from class java.lang.Object

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

Field Detail

NAME

public static final String NAME

The name of the filter. This should match a cache name in ehcache.xml

See Also:

Constant Field Values

Constructor Detail

SimplePageCachingFilterWithBlankPageProblem

public SimplePageCachingFilterWithBlankPageProblem()

Method Detail

doFilter

protected void doFilter(javax.servlet.http.HttpServletRequest request,
                        javax.servlet.http.HttpServletResponse response,
                        javax.servlet.FilterChain chain)
                 throws Exception

Performs the filtering for a request. This method caches based responses keyed by CachingFilter.calculateKey(javax.servlet.http.HttpServletRequest)

By default this method will queue requests requesting the page response for a given key until the first thread in the queue has completed. The request which occurs when the page expires incurs the cost of waiting for the downstream processing to return the respone.

The maximum time to wait can be configured by setting setTimeoutMillis on the underlying BlockingCache.

Overrides:

doFilter in class CachingFilter

Throws:

AlreadyGzippedException - if a double gzip is attempted

AlreadyCommittedException - if the response was committed on the way in or the on the way back

FilterNonReentrantException - if an attempt is made to reenter this filter in the same request.

net.sf.ehcache.constructs.blocking.LockTimeoutException - if this request is waiting on another that is populating the cache entry and timeouts while waiting. Only occurs if the BlockingCache has a timeout set.

Exception - for all other exceptions. They will be caught and logged in Filter.doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)