XSL check if some specific outpur were already generated - json

Question

I'm trying to convert some existing XML files to a JSON structure using XSL. Depending on their values, I need to put some elements into an JSON Array. To Produce a JSON String with correct syntax, I need to dynamically decide whether to put a comma behind (or in front) an object, since JSON doesn't allow trailing commas in arrays.
The XML files look somewhat like the following:
<list>
<type_a>
<active>0</active>
<data_a>don't put me to JSON...</data_a>
</type_a>
<type_b>
<active>1</active>
<data_b>put me to JSON</data_b>
</type_b>
<type_c>
<active>1</active>
<data_c>me too...</data_c>
</type_c>
</list>
The XSL to convert this looks like the following:
<xsl:template match="/list">
[
<xsl:if test="type_a/active != 0">
{ "type": "type_a",
"data": <xsl:value-of select="type_a/data_a" /> }
</xsl:if>
<xsl:if test="type_b/active != 0">
{ "type": "type_b",
"data": <xsl:value-of select="type_b/data_b" /> }
</xsl:if>
<xsl:if test="type_c/active != 0">
{ "type": "type_c",
"data": <xsl:value-of select="type_c/data_c" /> }
</xsl:if>
]
</xsl:template>
The Problem is, that I need to put commas between the different { } objects, but not after the last active one. The only two solutions I see are, either to check if any of the preceding objects where active, before putting an object (<xsl-if test="type_a/active != 0 or type_b/active != 0">, </xsl-if>; in front of the third object) or to transfer the XML into some, less odd, intermediate XML first. Particular the first option would be extremely ugly, since in reality I have to check for far more than 3 object types. The XML Format is produced by some legacy application and can't be changed.
Should I expect any further trouble because of using XSL to transfer the XML Structure to some none XML output?

Answer 1

One way is to check the preceding sibling to see if it is exists and is active and if so insert a ,. I have edited your template to reflect this, but I would write a function to just pass the node to, to make you life easier instead of repeating the template for each sibling.
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:func="http://example.com/function"
exclude-result-prefixes="xs"
version="2.0">
<xsl:output encoding="UTF-8" indent="yes" method="xml"/>
<xsl:template match="/list">
[
<xsl:sequence select="func:processing(type_a)"/>
<xsl:sequence select="func:processing(type_b)"/>
<xsl:sequence select="func:processing(type_c)"/>
]
</xsl:template>
<xsl:function name="func:processing">
<xsl:param name="type"/>
<xsl:for-each select="$type">
<xsl:if test="active != 0">
{ "type": <xsl:value-of select="local-name()" />,
"data": <xsl:value-of select="data_a" /> }
<xsl:if test="following-sibling::*[1] and following-sibling::*[1]/active!=0">
,
</xsl:if>
</xsl:if>
</xsl:for-each>
</xsl:function>
</xsl:stylesheet>