XSL remove empty nodes

Below are two neat XSL snippets that I wrote a few years back that remove empty nodes in a transformation.

Sometimes, XML payloads may contain tens or even hundreds of NULL elements, such as the following example:

<Person>

  <FirstName>Ahmed</FirstName>

  <MiddleName/>

  <LastName>Aboulnaga</LastName>

  <CompanyInfo>

    <CompanyName>IPN Web</CompanyName>

    <Title/>

    <Department>

      <DepartmentId/>

      <DepartmentName/>

      <DepartmentLocation/>

    </Department>

  </CompanyInfo>

</Person>

For performance reasons, it may be best just to remove these NULL elements by removing these empty nodes, resulting in a payload that is much smaller in size such as:

<Person>

  <FirstName>Ahmed</FirstName>

  <LastName>Aboulnaga</LastName>

  <CompanyInfo>

    <CompanyName>IPN Web</CompanyName>

  </CompanyInfo>

</Person>

In some cases, the cost savings is huge. For example, the first payload is 279 bytes while the second one, after removing empty nodes, is 148 bytes. This resulted in a 47% decrease in message size. In a high volume environment, that's 47% less memory needed, 47% less network bandwidth needed, and 47% less database space needed.

In regards to the snippets below, either add them as a new transformations in your SOA code, or include them in an existing one. I suggest you trying them out yourselves and comparing to see which one works best for you.

This first one works great, but removes all empty nodes up the root element. This has caused issues in the case where there is no data in the payload at all. But try it to see if it suits your needs, as it has worked great for us in the past:

<?xml version = '1.0'?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0" xmlns:dvm="http://www.oracle.com/XSL/Transform/java/oracle.tip.dvm.LookupValue">

  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="@*|node()">

    <xsl:if test=". != '' or ./@* != ''">

      <xsl:copy>

        <xsl:apply-templates select="@*|node()"/>

      </xsl:copy>

    </xsl:if>

  </xsl:template>

</xsl:stylesheet>

This was later updated by a client of mine to keep at least the root element of every tree to avoid the scenario above. Since it is more cautious in nature, it does not remove every NULL element, but avoids the single pitfall in the transformation above:

<?xml version = '1.0'?>

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0" xmlns:dvm="http://www.oracle.com/XSL/Transform/java/oracle.tip.dvm.LookupValue">

  <xsl:output method="xml" indent="yes" />

    <xsl:template match="@*|node()">

      <xsl:copy>

        <xsl:apply-templates select="@*|node()"/>

      </xsl:copy>

    </xsl:template>

  <xsl:template match="@*[.='']"/>

  <xsl:template match="*[not(node())]"/>

</xsl:stylesheet>