Recently I ran into an issue with a XSD that I had generated by using our modelling tool. It appeared the XSD did not match with my wishes so I had to modify the XSD. Now I could do this by hand quite easily but that would mean I had to redo it every time I regenerated the XSD after a model change. So I decided to use XSLT for the modifications. I have used XSLT quite extensively at previous projects but these where about 8 years ago and it just made me realize how fast one looses his knowledge if you don’t use it anymore.
Anyway, to avoid this situation for the next few years I decided to post about the basics of XSLT that I used in this situation so I always have a reference to get back at. The situation was that an XSD was generated but it was lacking several things:
- no use of namespaces (both import and prefixes)
- names of custom defined types didn’t end with the suffix ‘Type’
- some complex types were missing
And several more things but the idea stays the same.
Here is an example XSD that could be generated by the tool:
<?xml version="1.0" encoding="UTF-8"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:complexType name="Address"> <xs:sequence> <xs:element name="street" type="xs:string"/> <xs:element name="nr" type="xs:integer"/> <xs:element name="postalCode" type="myPostalCode"/> </xs:sequence> </xs:complexType> <xs:complexType name="Customer"> <xs:sequence> <xs:element name="firstName" type="xs:string" minOccurs="0"/> <xs:element name="lastName" type="xs:string"/> <xs:element name="address" type="Address"/> </xs:sequence> </xs:complexType> </xs:schema>
Here is how I would like the XSD to be look like:
<?xml version="1.0" encoding="UTF-8"?> <xs:schema xmlns:tns="htpp://www.pascalalma.net/customer" xmlns:xs="http://www.w3.org/2001/XMLSchema" targetNamespace="htpp://www.pascalalma.net/customer"> <xs:element name="customer" type="tns:CustomerType"/> <xs:complexType name="AddressType"> <xs:sequence> <xs:element name="street" type="xs:string"/> <xs:element name="nr" type="xs:integer"/> <xs:element name="postalCode" type="tns:myPostalCodeType"/> </xs:sequence> </xs:complexType> <xs:complexType name="CustomerType"> <xs:sequence> <xs:element name="firstName" type="xs:string" minOccurs="0"/> <xs:element name="lastName" type="xs:string"/> <xs:element name="address" type="tns:AddressType"/> </xs:sequence> </xs:complexType> <xs:complexType name="myPostalCodeType"> <xs:sequence> <xs:element name="firstPart"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:length value="4"/> </xs:restriction> </xs:simpleType> </xs:element> <xs:element name="secondPart"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:length value="2"/> </xs:restriction> </xs:simpleType> </xs:element> </xs:sequence> </xs:complexType> </xs:schema>
To get to this last XSD I used the following XSLT (see inline documentation for explanation):
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<!-- first copy the root and apply templates-->
<xsl:template match="/">
<xsl:copy>
<!-- copy the attributes (if any) of the root element -->
<xsl:copy-of select="@*"/>
<xsl:apply-templates/>
</xsl:copy>
</xsl:template>
<!-- match any other element and copy it with the attributes -->
<xsl:template match="*">
<xsl:copy>
<xsl:copy-of select="@*"/>
<xsl:apply-templates/>
</xsl:copy>
</xsl:template>
<!-- Add the necessary namespaces to the root of the schema -->
<xsl:template match="xs:schema">
<!-- Recreate the xs:schema element-->
<xsl:element name="xs:schema">
<!-- Copy the existing attributes in the original xs:schema element to this one -->
<xsl:copy-of select="@*"/>
<!-- add Namespace -->
<xsl:namespace name="tns">htpp://www.pascalalma.net/customer</xsl:namespace>
<xsl:attribute name="targetNamespace">htpp://www.pascalalma.net/customer</xsl:attribute>
<!-- add toplevel element -->
<xsl:element name="xs:element">
<xsl:attribute name="name">customer</xsl:attribute>
<xsl:attribute name="type">tns:CustomerType</xsl:attribute>
</xsl:element>
<!-- continue with matching al child elements of the xs:schema element-->
<xsl:apply-templates/>
<!-- call a custom template to add an extra complexType to the schema that couldn't be generated by the modelling tool-->
<xsl:call-template name="addPostalCodeType"/>
</xsl:element>
</xsl:template>
<!-- suffix all complexType names with 'Type' -->
<xsl:template match="xs:complexType">
<xsl:choose>
<!-- Check if the type already has the suffix 'Type' -->
<xsl:when test="substring(@name, (string-length(@name)-3)) = 'Type'">
<!-- if so, just copy the existing attributes -->
<xsl:copy>
<xsl:copy-of select="@*"/>
<xsl:apply-templates/>
</xsl:copy>
</xsl:when>
<xsl:otherwise>
<!-- if not, copy all attribute and overwrite the attribute 'name' so the suffix 'Type' is added-->
<xsl:copy>
<xsl:copy-of select="@*"/>
<xsl:attribute name="name"><xsl:value-of select="@name"/>Type</xsl:attribute>
<xsl:apply-templates/>
</xsl:copy>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<!-- Prefix all types with 'tns:'. All default xs: types are untouched. -->
<xsl:template match="xs:element">
<!-- Create a variable with the name of the type of the element in it. It appears this 'type' attribute
can be of different types so take this into account -->
<xsl:variable name="elementType">
<xsl:choose>
<xsl:when test="@type instance of xs:string or @type instance of xs:untypedAtomic">
<xsl:choose>
<xsl:when test="contains(@type,':')">
<xsl:value-of select="substring-after(@type,':')"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="@type"/>
</xsl:otherwise>
</xsl:choose>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="@type"/>
</xsl:otherwise>
</xsl:choose>-->
</xsl:variable>
<!-- Create a variable with the namespace prefix of the attribute if any. -->
<xsl:variable name="elementTypePrefix">
<xsl:choose>
<xsl:when test="@type instance of xs:QName">
<xsl:value-of select="prefix-from-QName(@type)"/>
</xsl:when>
<xsl:when test="@type instance of xs:string">
<xsl:value-of select="substring-before(@type,':')"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="substring-before(@type,':')"/>
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<!-- Now the variables are filled we can use it to determine if we need to add a prefix -->
<xsl:choose>
<!-- if type starts with xs: the prefix must not be changed -->
<xsl:when test="$elementTypePrefix = 'xs'">
<xsl:copy>
<xsl:copy-of select="@*"/>
<xsl:apply-templates/>
</xsl:copy>
</xsl:when>
<xsl:otherwise>
<xsl:copy>
<xsl:copy-of select="@*"/>
<!-- A few steps back we renamed complextypes so they ended with 'Type'. Now we have to suffix the places
where the types are reffered also with 'Type' -->
<xsl:if test="substring($elementType, (string-length($elementType)-3)) != 'Type'">
<xsl:attribute name="type">tns:<xsl:value-of select="@type"/>Type</xsl:attribute>
</xsl:if>
<xsl:if test="substring($elementType, (string-length($elementType)-3)) = 'Type'">
<xsl:attribute name="type">tns:<xsl:value-of select="@type"/></xsl:attribute>
</xsl:if>
<xsl:apply-templates/>
</xsl:copy>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<!-- The next template generates the complexType 'myPostalCodeType' when the template is called -->
<xsl:template name="addPostalCodeType">
<xsl:element name="xs:complexType">
<xsl:attribute name="name">myPostalCodeType</xsl:attribute>
<xsl:element name="xs:sequence">
<xsl:element name="xs:element">
<xsl:attribute name="name">firstPart</xsl:attribute>
<xsl:element name="xs:simpleType">
<xsl:element name="xs:restriction">
<xsl:attribute name="base">xs:string</xsl:attribute>
<xsl:element name="xs:length">
<xsl:attribute name="value">4</xsl:attribute>
</xsl:element>
</xsl:element>
</xsl:element>
</xsl:element>
<xsl:element name="xs:element">
<xsl:attribute name="name">secondPart</xsl:attribute>
<xsl:element name="xs:simpleType">
<xsl:element name="xs:restriction">
<xsl:attribute name="base">xs:string</xsl:attribute>
<xsl:element name="xs:length">
<xsl:attribute name="value">2</xsl:attribute>
</xsl:element>
</xsl:element>
</xsl:element>
</xsl:element>
</xsl:element>
</xsl:element>
</xsl:template>
</xsl:stylesheet>
Although this example might be very specific and there are better ways to obtain similar results, to me this might be a handy reminder how to solve an issue with XSLT and perhaps it might even help you in some way. In another post I will show how I do this translation in Maven and also how to validate the outcome.
The Pragmatic Integrator 