[FOP-2342] Make image from URL abide no-cache HTTP headers

• Type: Improvement
• Status: Reopened
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 1.1
• Component/s: image/unqualified
• Labels: http-headers image
• Environment: Tested on CentOS, Tomcat6 and FOP 1.1rc1 service
• Assignee: Unassigned
• Reporter: The BitSmith
• Created: 14/Feb/14 09:39
• Updated: 14/Feb/14 12:55

Description

When I include an image, it is cached. So including a dynamic image shows only the first version of the image. To prevent this, I have to add a constantly changing parameter (called "nonce" here):

<fo:external-graphic width="140mm" height="30mm" content-width="scale-down-to-fit" content-height="scale-down-to-fit" inline-progression-dimension.maximum="100%" scaling="uniform" vertical-align="-50%">
<xsl:variable name="orgguid" select="Organization/ID" />
<xsl:variable name="nonce" select="Nonce" />
<xsl:variable name="logo" select="concat('http://localhost/images/fopimages/logo.php?orgid=', $orgguid, '&dummy=', $nonce)"/>
<xsl:attribute name="src">url(<xsl:value-of select="$logo"/>)</xsl:attribute>
</fo:external-graphic>

This happens despite the fact that the PHP script that produces the image sends "no-cache" headers (PHP code):

header('Expires: Fri, 13 May 1983 18:30:00 GMT');
header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT');
header('Cache-Control: no-store, no-cache, must-revalidate'); // HTTP/1.1
header('Cache-Control: post-check=0, pre-check=0', FALSE);
header('Pragma: no-cache'); // HTTP/1.0
header('Content-Type: ' . $this->mstrLogoType);
header('Content-Length: ' . strlen($this->mmixLogoData));
header('Content-Disposition: inline');
header('X-Content-Type-Options: nosniff'); // Workaround for IE bug.
echo $this->mmixLogoData;

It would be nice if the image caching mechanism would abide these headers, so workarounds like extra parameters are not necessary.