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

Subject: Re: [xsl] JSON-encoding strings in XSLT 2.0
From: Hermann Stamm-Wilbrandt <STAMMW@xxxxxxxxxx>
Date: Wed, 6 Nov 2013 15:18:28 +0100

DataPower appliance had this cascade of  regexp:relace()  statements in the
past in stylesheet "store:///jsonx2json.xsl" for "<json:string>" escaping.

Customer raised a PMR on bad performance for JSONX <json:string>
to JSON (he proved by using stylesheet profiling).

I did fix that in this May fixpack by introducing new extension function
for doing the escaping in firmware rather than XSLT and just calling that
"dp:encode(., 'json-escape')":

This improved conversion runtime for a 2.2MB JSONX customer sample file
with 740KB JSON output by a factor of 11.

So if you have to do JSON escaping in XSLT, you have no choice.
If not, then better do it in a new extension function.

Mit besten Gruessen / Best wishes,

Hermann Stamm-Wilbrandt
Level 3 support for XML Compiler team and Fixpack team lead
WebSphere DataPower SOA Appliances
https://twitter.com/HermannSW/     http://www.stamm-wilbrandt.de/ce/
IBM Deutschland Research & Development GmbH
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschaeftsfuehrung: Dirk Wittkopp
Sitz der Gesellschaft: Boeblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294

  From:       Michael Kay <mike@xxxxxxxxxxxx>

  To:         xsl-list@xxxxxxxxxxxxxxxxxxxxxx,

  Date:       10/29/2013 12:46 PM

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

On 29 Oct 2013, at 11:02, Martynas Jusevihius <martynas@xxxxxxxxxxxx>

> 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

>  <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"/>

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;') ! ....."/>

Michael Kay

>        <xsl:value-of
> select="replace(replace(replace(replace(replace(replace(., '\\',
> '\\\\'), '''', '\\'''), '&quot;', '\\&quot;'), '&#09;', '\\t'),
> '&#10;', '\\n'), '&#13;', '\\r')"/>

> 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 Jusevihius <martynas@xxxxxxxxxxxx>
>>> 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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