good point.   too focused on jcs     not realizing it is a file system issue.

--- On Thu, 1/5/12, Thomas Vandahl <t...@apache.org> wrote:

From: Thomas Vandahl <t...@apache.org>
Subject: [JCS] Re: JCS Key Length Issue -- limited to 256 characters long?
To: u...@commons.apache.org
Cc: "JCS Users List" <jcs-users@jakarta.apache.org>
Date: Thursday, January 5, 2012, 4:48 AM

First of all: Please use u...@commons.apache.org for questions regarding
JCS.

On 04.01.12 18:12, Chopin hu wrote:
> I have a program to download files from remote sites.   Once downloaded a 
> data file, I use the URL as a key and put it to the cache so that I don't 
> have to download it again if the url is found to exist in the 
> cache.   However, I found sometimes the caching would fail -- no caching is 
> put to the file system ( I am using Disk File Cache).   the url is working 
> fine for downloading.   After debugging, it turns out that the URL string is 
> too long.   When the url string exceeds 256 characters, JCS won't accept it 
> as a proper key.   
> 
> So my questions are:
> 1.) is a JCS cache key limited to 256 chars long?   is there a way to 
> increase its length?
> 2.) If can not get around the cache key length limitation, what could be the 
> possible ways to make a long URL string short enough but still unique enough 
> to serve as a key?  I tried to use the last 256 characters from the url 
> string, but some query string is so long that it could not guarantee a key's 
> uniqueness.

I guess the FileDiskCache is the issue here. The key of the item in
FileDiskCache is directly used as a file name. So what you experience is
a limit of file name length rather than key length.

You should better use another disk cache implementation such as
IndexedDiskCache which does not have such limits.

Bye, Thomas.

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