How to include an XSL file into another XSL file

Question

I need that 2.xsl file use function for changing date format (tag <Date> ) from file 1.xsl . I use instruction <xsl:include> but I don't know what I should to change.

Here is my XML file:

<?xml version="1.0" encoding="UTF-8"?>
<ClientList>
    <Client>
        <Name>Jan</Name>
        <Surname>Kowalski</Surname>
        <Date>2018-03-23</Date>
    </Client>
    <Client>
        <Name>Piotr</Name>
        <Surname>Nowak</Surname>
        <Date>2018-04-25</Date>
    </Client>
</ClientList>

My 1.xsl file with function that changes date format:

<?xml version='1.0'?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" indent="yes"/>
    <Date>
        <xsl:value-of select="concat(substring(Date, 9, 2), '-', substring(Date, 6, 2), '-', substring(Date, 1, 4))"/>
    </Date>
</xsl:stylesheet>

Here is my 2.xsl file (I need that this file use function from 1.xsl ):

<?xml version='1.0'?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="xml" indent="yes"/>
    <xsl:include href="1.xsl"/>

    <xsl:template match="/">
        <ClientList>
            <xsl:for-each select="ClientList/Client">
                <Client>
                    <NameSurname>
                        <xsl:value-of select="concat(Name, ' ' , Surname)"/>
                    </NameSurname>
                </Client>
            </xsl:for-each>
        </ClientList>
    </xsl:template>
</xsl:stylesheet>

Answer 1

There are couple of issues with the XSLs created and rightly pointed out by @Martin Honnen in his comment related to 1.xsl .

The <Date> format conversion logic needs to be wrapped inside an <xsl:template> or <xsl:function> . Below is the updated 1.xsl that uses <xsl:template> .

<xsl:template name="DateConvertor">
    <Date>
        <xsl:value-of select="concat(substring(Date, 9, 2), '-', substring(Date, 6, 2), '-', substring(Date, 1, 4))"/>
    </Date>
</xsl:template>

In 2.xsl , you are including utils.xsl which I believe corresponds to 1.xsl . In this XSL, you need to invoke the template or function that you have created in the included XSL.

<xsl:template match="/">
    <ClientList>
        <xsl:for-each select="ClientList/Client">
            <Client>
                <NameSurname>
                    <xsl:value-of select="concat(Name, ' ', Surname)" />
                </NameSurname>
                <xsl:call-template name="DateConvertor" /> <!-- call the template here -->
            </Client>
        </xsl:for-each>
    </ClientList>
</xsl:template>

EDIT - Changes for using <xsl:function>

XSLT 2.0 allows writing of own functions using <xsl:function> . Functions can be used for performing any computational logic and they return values based on the computations. Parameters can be passed to the function using <xsl:param> . Functions have to be associated to a namespace which is different than the XSLT namespace.

The 1.xsl will need to be modified to include a function which accepts a single parameter of type string and returns a value which is of type string .

<xsl:function name="ex:DateConvertor" as="xs:string">
    <xsl:param name="InputDate" as="xs:string" />
    <xsl:value-of select="concat(substring($InputDate, 9, 2), '-', substring($InputDate, 6, 2), '-', substring($InputDate, 1, 4))"/>
</xsl:function>

This function is associated with namespace xmlns:ex="http://canbeanything" . Additionally since the datatypes are being used for the parameter and return value, you need to define namespace xmlns:xs="http://www.w3.org/2001/XMLSchema" also.

<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:ex="http://canbeanything">

Changes in 2.xsl to invoke the function ex:DateConvertor .

Map the namespace necessary for the function.

<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:ex="http://canbeanything">

Call Function and pass Date value as a parameter

<xsl:template match="/">
    <ClientList>
        <xsl:for-each select="ClientList/Client">
            <Client>
                <NameSurname>
                    <xsl:value-of select="concat(Name, ' ', Surname)" />
                </NameSurname>
                <!-- Function Call -->
                <!-- passing value of 'Date' as parameter -->
                <Date>
                    <xsl:value-of select="ex:DateConvertor(Date)" /> 
                </Date>
            </Client>
        </xsl:for-each>
    </ClientList>
</xsl:template>

The required output can be achieved in a single XSL, but I am assuming that this is a learning phase and the above is probably an example of <xsl:include> .