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From "Christopher Bradford (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HTTPCLIENT-1099) Overriding Caching Policies
Date Tue, 09 Feb 2016 20:52:18 GMT

    [ https://issues.apache.org/jira/browse/HTTPCLIENT-1099?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15139730#comment-15139730
] 

Christopher Bradford commented on HTTPCLIENT-1099:
--------------------------------------------------

Recently I have been working on an application where all responses should be cached. The service
being pulled returns the header {{Cache-Control: private, no-cache="Set-Cookie"}} which appears
to trigger a {{true}} response from {{ResponseCachingPolicy.isExplicitlyNonCacheable}}.

Should I be able to implement my own {{ResponseCachingPolicy}} and configure the {{CacheConfig}}
with it? I would happily commit some of my time to refactor the code to make this possible.

> Overriding Caching Policies
> ---------------------------
>
>                 Key: HTTPCLIENT-1099
>                 URL: https://issues.apache.org/jira/browse/HTTPCLIENT-1099
>             Project: HttpComponents HttpClient
>          Issue Type: Improvement
>          Components: HttpCache
>    Affects Versions: 4.1.1
>            Reporter: Bart Robeyns
>            Assignee: Jon Moore
>            Priority: Minor
>              Labels: cache, policy
>             Fix For: Future
>
>         Attachments: OpenPolicies.patch
>
>
> It is not possible to alter the behaviour of the CachingHttpClient because the policies
defining the behaviour are private and tied directly to specific implementations in the CachingHttpClients
constructor. Furthermore, these policies are package private, discouraging reuse and/or extensions.
> Making this possible is easy enough (provide some policy-setters or -constructor-args
in CachingHttpClient and make the policy-classes public); the attached patch allows custom
Policies, extending the default ones to be set on the CacheConfig class.
> The specific case that led to this question:
> A back-end application only sets its Content-Length header for responses below 8K. This
response does get stored in the cache, but when retrieving it from the cache, CacheValidityPolicy.contentLengthHeaderMatchesActualLength
checks the Content-Length header with the stored size (to verify whether the cached content
is complete). This check fails, causing the cache entry to be deemed unusable. If we were
able to provide our own subclassed CacheValidityPolicy, it would be easy to skip the check
if the header is missing and thus accomodate this specific back-end quirk.



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