If you know what entities will be used and how they are defined, you can do the following (quite primitive and error-prone, but still better than nothing):
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:my="my:my">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:character-map name="mapEntities">
<xsl:output-character character="&" string="&"/>
</xsl:character-map>
<xsl:variable name="vEntities" select=
"'stackoverflow',
'How can I preserve the entity reference when transforming with XSLT\?\?'
"/>
<xsl:variable name="vReplacements" select=
"'&so;', '&question;'"/>
<xsl:template match="node()|@*">
<xsl:copy>
<xsl:apply-templates select="node()|@*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="https://stackoverflow.com/">
<xsl:text disable-output-escaping="yes"><![CDATA[<!DOCTYPE doc [ <!ENTITY so "stackoverflow">
<!ENTITY question
"How can I preserve the entity reference when transforming with XSLT??"> ]>
]]>
</xsl:text>
<xsl:apply-templates/>
</xsl:template>
<xsl:template match="text()">
<xsl:value-of select=
"my:multiReplace(.,
$vEntities,
$vReplacements,
count($vEntities)
)
" disable-output-escaping="yes"/>
</xsl:template>
<xsl:function name="my:multiReplace">
<xsl:param name="pText" as="xs:string"/>
<xsl:param name="pEnts" as="xs:string*"/>
<xsl:param name="pReps" as="xs:string*"/>
<xsl:param name="pCount" as="xs:integer"/>
<xsl:sequence select=
"if($pCount > 0)
then
my:multiReplace(replace($pText,
$pEnts[1],
$pReps[1]
),
subsequence($pEnts,2),
subsequence($pReps,2),
$pCount -1
)
else
$pText
"/>
</xsl:function>
</xsl:stylesheet>
when applied on the provided XML document:
<!DOCTYPE doc [ <!ENTITY so "stackoverflow">
<!ENTITY question
"How can I preserve the entity reference when transforming with XSLT??"> ]>
<doc>
<text>Hello &so;!</text>
<text>&question;</text>
</doc>
the wanted result is produced:
<!DOCTYPE doc [ <!ENTITY so "stackoverflow">
<!ENTITY question
"How can I preserve the entity reference when transforming with XSLT??"> ]>
<doc>
<text>Hello &so;!</text>
<text>&question;</text>
</doc>
Do note:
-
The special (RegEx) characters in the replacements must be escaped.
-
We needed to resolve to DOE, which isn’t recommended, because it violates the principles of the XSLT architecture and processing model — in other words this solution is a nasty hack.