[WSO2 ESB] XSLT mediator : Writing a simple style sheet

The XSLT Mediator of WSO2 ESB applies a specified XSLT transformation to a selected element of the current message payload. In this post i am going to write a simple XSLT style sheet which will read values from the current XML payload inside ESB using XPath and populate them into style sheet to create a new or different payload.

Below is our original XML payload.

We will be passing this payload into XSLT mediator with specifying a certain drink name as a parameter to the style sheet. For e.g i am passing drink name as 'Coffee'. At the style sheet it will traverse through incoming payload and find the <lunch> elements which contains 'Coffee' as drink name. If matches found we add the prices of those elements under a new <Payment> element. So when we come out of XSLT mediator the payload will be now changed to the <Payment> entry where it contains drinkPrices of matching elements.

The style sheet 'discountPayment.xsl' is like this.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:fn="http://www.w3.org/2005/02/xpath-functions" xmlns:m0="http://services.samples" version="2.0" exclude-result-prefixes="m0 fn">
        <xsl:output method="xml" omit-xml-declaration="yes" indent="yes"/>
        <xsl:param name="drink_name"/>
        <xsl:template match="/">
            <Payment>
                <xsl:for-each select="//Order/lunch[contains(drinkName, $drink_name)]">
                    <discount>
                        <xsl:value-of select="drinkPrice"/>
                    </discount>
                </xsl:for-each>
            </Payment>
        </xsl:template>
</xsl:stylesheet>

Add this style sheet into local-entries of ESB and it can be referred from XSLT mediator as this.

After coming out from XSLT mediator now our current message payload is changed to below.