XSLT insert at right location - xslt

Question

My input XML is as follows. Basically the XML has various <servlet> tags. My requirement is to apply a XSLT transform which browses through <servlet-name> tags and see if a particular servlet with specified name exists. If it exists then i need to see that tag <B> under that particular servlet with a <param-name>does not EXIST. If the tag with a specific <param-name> under the searched doesn't exist then i add the tag <B>NEW</B> along with other <B> tags of that particular servlet else i do not perform any action.
INPUT XML
<web-app metadata-complete="true">
<servlet>
<servlet-name>AAA</servlet-name>
<servlet-class>com.AAA</servlet-class>
<B>
<param-name>port</param-name>
<param-value>8802</param-value>
</B>
<B>
<param-name>connectors-xml</param-name>
<param-value/>
</B>
<B>
<param-name>webservices-xml</param-name>
<param-value/>
</B>
<B>
<param-name>exposure-server</param-name>
<param-value/>
</B>
<some-tag>1</some-tag>
</servlet>
<servlet>
<servlet-name>BBB</servlet-name>
<servlet-class>com.BBB</servlet-class>
<B>
<param-name>port</param-name>
<param-value>8802</param-value>
</B>
<B>
<param-name>connectors-xml</param-name>
<param-value/>
</B>
<B>
<param-name>webservices-xml</param-name>
<param-value/>
</B>
<B>
<param-name>exposure-server</param-name>
<param-value/>
</B>
<some-tag>2</some-tag>
</servlet>
<C>
<D>
</D
</C>
<junk-tag>
<tag1>BASIC</tag1>
<tag2>BASIC</tag2>
</junk-tag>
</web-app>
eg. Lets say i search for a Servlet with Servlet name as "BBB" below. If found, then i check that its <B> tag with <param-name> value XXX doesn't exist then i add it so that o/p looks as below. If "BBB" <servlet-name> has <B> tag with <param-name> value XXX already present then i do not do anything.
OUTPUT.XML
<web-app metadata-complete="true">
<servlet>
<servlet-name>AAA</servlet-name>
<servlet-class>com.AAA</servlet-class>
<B>
<param-name>port</param-name>
<param-value>8802</param-value>
</B>
<B>
<param-name>connectors-xml</param-name>
<param-value/>
</B>
<B>
<param-name>webservices-xml</param-name>
<param-value/>
</B>
<B>
<param-name>exposure-server</param-name>
<param-value/>
</B>
<some-tag>1</some-tag>
</servlet>
<servlet>
<servlet-name>BBB</servlet-name>
<servlet-class>com.BBB</servlet-class>
<B>
<param-name>port</param-name>
<param-value>8802</param-value>
</B>
<B>
<param-name>connectors-xml</param-name>
<param-value/>
</B>
<B>
<param-name>webservices-xml</param-name>
<param-value/>
</B>
<B>
<param-name>exposure-server</param-name>
<param-value/>
</B>
<B>NEW</B>
<some-tag>2</some-tag>
</servlet>
<C>
<D>
</D
</C>
<junk-tag>
<tag1>BASIC</tag1>
<tag2>BASIC</tag2>
</junk-tag>
</web-app>
I have tried writing a XSLT but somehow caught in BUGS and syntax issues
<xsl:template match="web-app/servlet[servlet-name='BBB/B']">
<xsl:copy-of select="."/>
<xsl:choose>
<xsl:when test="not(/web-app/servlet[servlet-name='BBB']/B[param-name='XXX'])">
<B>NEW</B>
</xsl:when>
</xsl:choose>
</xsl:template>
Any guidance? I am NOVICE to XSLT and attempting by googling itself.

Answer 1

The expression you want is just not(B[param-name='XXX']) as you are already positioned on the relevant servlet at the point, so this expression will be relevant to that. Additionally your current code will copy the existing servlet and add <B>NEW</B> after it, when in fact you want it as a child.
So you could do this....
<xsl:template match="web-app/servlet[servlet-name='BBB']">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
<xsl:if test="not(B[param-name='XXX'])">
<B>NEW</B>
</xsl:if>
</xsl:copy>
</xsl:template>
Or better still, put the check in the template match itself
<xsl:template match="web-app/servlet[servlet-name='BBB'][not(B[param-name='XXX'])]">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
<B>NEW</B>
</xsl:copy>
</xsl:template>
(Both of these assume you are also using the identity template)
However, this adds your new tag after <some-tag>2</some-tag> which may not be what you want.
If you want to place it after the last B element, you should change the template to match the last B element instead.
<xsl:template match="web-app/servlet[servlet-name='BBB'][not(B[param-name='XXX'])]/B[last()]">
<xsl:copy-of select="." />
<B>NEW</B>
</xsl:template>
Try this XSLT
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">
<xsl:output method="xml" indent="yes" />
<xsl:template match="web-app/servlet[servlet-name='BBB'][not(B[param-name='XXX'])]/B[last()]">
<xsl:copy-of select="." />
<B>NEW</B>
</xsl:template>
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>