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Re: [xsl] JSON-encoding strings in XSLT 2.0


Subject: Re: [xsl] JSON-encoding strings in XSLT 2.0
From: Martynas Jusevičius <martynas@xxxxxxxxxxxx>
Date: Wed, 20 Nov 2013 01:42:59 +0100

Michael,

I now realised this solution was incomplete. I have to pass a piece of
XHTML as a string into a WYSIWYG editor constructor, so not only the
characters inside text nodes are significant, but also the markup
itself. For example, the quotes surrounding attributes have to be
escaped for JSON as well. I ended up with a solution involving
xml-to-string.xsl [1] and disable-output-escaping="yes":

                <script type="text/javascript">
                jQuery(function() {
                    jQuery('#textarea').wymeditor(
                    <xsl:if test="xhtml:div/*">
                        <xsl:text>{ html: '</xsl:text>
                        <xsl:variable name="escaped-xhtml">
                            <xsl:apply-templates select="xhtml:div/*"
mode="xml-to-string"/>
                        </xsl:variable>
                        <xsl:variable name="escaped-json">
                            <xsl:call-template name="json-escape">
                                <xsl:with-param name="string"
select="$escaped-xhtml"/>
                            </xsl:call-template>
                        </xsl:variable>
                        <xsl:value-of disable-output-escaping="yes"
select="$escaped-json"/>
                        <xsl:text>' }</xsl:text>
                    </xsl:if>)
                });
                </script>

    <xsl:template name="json-escape">
        <xsl:param name="string" as="xs:string?"/>
        <xsl:variable name="string" select="replace($string, '\\', '\\\\')"/>
        <xsl:variable name="string" select="replace($string, '&quot;',
'\\&quot;')"/>
        <xsl:variable name="string" select="replace($string, '''', '\\''')"/>
        <xsl:variable name="string" select="replace($string, '&#09;',
'\\t')"/>
        <xsl:variable name="string" select="replace($string, '&#10;',
'\\n')"/>
        <xsl:variable name="string" select="replace($string, '&#13;',
'\\r')"/>

        <xsl:value-of select="$string"/>
    </xsl:template>

It works, but seems rather fragile to me. I wonder if there is a better way?

[1] http://lenzconsulting.com/xml-to-string/

Martynas
graphityhq.com

On Tue, Oct 29, 2013 at 12:46 PM, Michael Kay <mike@xxxxxxxxxxxx> wrote:
>
> On 29 Oct 2013, at 11:02, Martynas JuseviD
ius <martynas@xxxxxxxxxxxx>
wrote:
>
>> Thanks Michael. I was looking at http://json.org and here's what I came up
with:
>>
>>    <xsl:template match="text()" mode="json-identity">
>>        <xsl:value-of
>> select="replace(replace(replace(replace(replace(replace(., '\\',
>> '\\\\'), '''', '\\'''), '&quot;', '\\&quot;'), '&#09;', '\\t'),
>> '&#10;', '\\n'), '&#13;', '\\r')"/>
>>    </xsl:template>
>>
>> Can this be improved?
>
> Well, I'm not going to check that the list of characters to be escaped is
complete, but you've got the right idea. I would code it like this for
readability:
>
>>  <xsl:template match="text()" mode="json-identity">
>        <xsl:variable name="v" select="."/>
>        <xsl:variable name="v" select="replace($v, '\\', '\\\\')"/>
>        <xsl:variable name="v" select="replace($v, '&quot;', '\\&quot;')"/>
>        ...
>        <xsl:value-of select="$v"/>
> </xsl:variable>
>
> or in 3.0 you can use the "!" operator for function chaining:
>
>> <xsl:template match="text()" mode="json-identity">
>        <xsl:value-of select="replace(., '\\', '\\\\') ! replace(., '&quot;',
'\\&quot;') ! ....."/>
> </xsl:variable>
>
> Michael Kay
> Saxonica
>
>
>
>>        <xsl:value-of
>> select="replace(replace(replace(replace(replace(replace(., '\\',
>> '\\\\'), '''', '\\'''), '&quot;', '\\&quot;'), '&#09;', '\\t'),
>> '&#10;', '\\n'), '&#13;', '\\r')"/>
>    </xsl:template>
>
>>
>> On Tue, Oct 29, 2013 at 10:37 AM, Michael Kay <mike@xxxxxxxxxxxx> wrote:
>>>
>>> There's no built-in function for the job, but picking out the characters
=
>>> that need special treatment (e.g. replacing newline by "\n") isn't =
>>> difficult. Handling astral characters is a bit tricky because JSON =
>>> requires them to be represented as a surrogate pair, but again the logic
=
>>> for that isn't really difficult.
>>>
>>> Michael Kay
>>> Saxonica
>>>
>>> On 29 Oct 2013, at 00:56, Martynas JuseviD
ius <martynas@xxxxxxxxxxxx>
wrote:
>>>
>>>> Hey,
>>>>
>>>> is there some way in XSLT 2.0 to encode strings for use in JSON? In my
>>>> case, the stylesheet has to encode all text nodes in a XHTML fragment
>>>> which then gets passed to WYSIWYM editor constructor. Could this be
>>>> done as identity transform?
>>>>
>>>> I had solved this problem when I used XSLT 1.0 on PHP by calling
>>>> json_encode() as extension function, but now I'm in the Java world.
>>>> http://php.net/manual/en/function.json-encode.php
>>>>
>>>> Martynas
>>>> graphityhq.com


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