Camel with XSLT 2.0 and xsl:result-document keeping files in route destination

Question

I am trying to use a XSLT 2.0 transformation to split a XML file into smaller files based on groups of items. To execute the transformation I am using a camel route. My problem is that when the xslt transformation is run the resulting files are saved "outside" the route.

So, for example, given the following camel route:

from("{{input.endpoint}}")
.to("xslt:xslts/ics/MappingMapTostudents.xslt?saxon=true")
.to("{{output.endpoint}}");

I would be expecting the resulting xml files to be created in the {output.endpoint} folder. Unfortunately saxon is saving the files in the root folder where the executable (camel app) is. How can I have the files saved to {{output.endpoint}} or better, passed on to the following endpoint?

Following an XML example:

<?xml version="1.0" encoding="UTF-8"?>
<class> 
    <students>
        <student>
            <firstname>Albert</firstname> 
            <group>A</group>
        </student> 
        <student> 
            <firstname>Isaac</firstname> 
            <group>A</group>
        </student> 
        <student> 
            <firstname>Leonardo</firstname> 
            <group>B</group>
        </student> 
        <student>
            <firstname>Enrico</firstname> 
            <group>B</group>
        </student> 
        <student> 
            <firstname>Marie</firstname> 
            <group>C</group>
        </student> 
        <student> 
            <firstname>Rosalind</firstname> 
            <group>C</group>
        </student>
        <student> 
            <firstname>Ada</firstname> 
            <group>D</group>
        </student>
    </students>
</class>

The XSLT transformation:

<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:grp="http://www.altova.com/Mapforce/grouping" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:fn="http://www.w3.org/2005/xpath-functions" exclude-result-prefixes="grp xs fn">
    <xsl:output method="xml" encoding="UTF-8" indent="yes"/>
    <xsl:function name="grp:var2_function">
        <xsl:param name="var1_param" as="node()"/>
        <xsl:for-each select="$var1_param/student">
            <xsl:sequence select="fn:string(group)"/>
        </xsl:for-each>
    </xsl:function>
    <xsl:template match="/">
        <xsl:for-each-group select="class/students" group-by="grp:var2_function(.)">
            <xsl:variable name="var3_resultof_grouping_key" as="xs:string" select="current-grouping-key()"/>
            <xsl:result-document href="{fn:concat($var3_resultof_grouping_key, '.xml ')}" encoding="UTF-8">
                <class>
                    <xsl:for-each select="(current-group()/student)[(fn:string(group) = $var3_resultof_grouping_key)]">
                        <students>
                            <student>
                                <firstname>
                                    <xsl:sequence select="fn:string(firstname)"/>
                                </firstname>
                                <group>
                                    <xsl:sequence select="$var3_resultof_grouping_key"/>
                                </group>
                            </student>
                        </students>
                    </xsl:for-each>
                </class>
            </xsl:result-document>
        </xsl:for-each-group>
    </xsl:template>
</xsl:stylesheet>

I don't know about the integration of Saxon with Apache Camel which I think is the key to getting the files in the desired location, but as for your stylesheet, the whole code is rather convoluted, you could reduce the grouping to ``. — Martin Honnen, Mar 14 '19 at 18:56
Hi Martin, thanks. The xslt file is generated with altova MapForce and it's just a proof of concept. My real xslt is far more complicated. — aldebaran-ms, Mar 15 '19 at 09:17

score 1 · Answer 1 · answered Mar 14 '19 at 20:24

I know very little about Apache-Camel, and unfortunately questions about the technology on StackOverflow don't seem to have a very high success rate.

The documentation at http://camel.apache.org/xslt.html gives no clue about how to set the base output URI, which is used by Saxon for resolving any relative URI appearing in xsl:result-document/@href.

The simplest approach that comes to mind is to pass a parameter to the transformation, whose value is the absolute path to the output directory:

<xsl:param name="outDir" as="xs:string"/>
...
<xsl:result-document 
   href="file:///{$outDir}{$var3_resultof_grouping_key}.xml"/>

But someone who knows Apache Camel might be able to suggest a more elegant solution.

Thanks Michael. That's what I have already done as a workaround but it's an ugly solution because it breaks my camel route and force me to split it in two segments. — aldebaran-ms, Mar 15 '19 at 09:14

score 1 · Answer 2 · answered Mar 15 '19 at 11:20

You may try to force an output of type "file".

to("xslt:xslts/ics/MappingMapTostudents.xslt?saxon=true&output=file")

Then, as the doc explains it, you have to fill a Camel header with the wanted target file path:

For file you must specify the filename in the IN header with the key Exchange.XSLT_FILE_NAME which is also CamelXsltFileName. Also any paths leading to the filename must be created beforehand, otherwise an exception is thrown at runtime.

Good luck

Camel with XSLT 2.0 and xsl:result-document keeping files in route destination

2 Answers2