How can I handle error Exception with try/catch using xslt 3.0 - xslt-3.0

Question

How can I handle error Exception with try/catch using xslt 3.0. I am finding in xml number Element. If number Element not find in parent product then generate a file error.txt and how to write the Exception.
Input XML
<?xml version="1.0" encoding="UTF-8"?>
<catalog>
<product dept="WMN">
<name language="en">Fleece Pullover</name>
<colorChoices>navy black</colorChoices>
</product>
<product dept="ACC">
<number>563</number>
<name language="en">Floppy Sun Hat</name>
</product>
<product dept="ACC">
<number>443</number>
<name language="en">Deluxe Travel Bag</name>
</product>
<product dept="MEN">
<number>784</number>
<name language="en">Cotton Dress Shirt</name>
<colorChoices>white gray</colorChoices>
<desc>Our <i>favorite</i> shirt!</desc>
</product>
</catalog>
Using XSLT
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:err="http://www.w3.org/2005/xqt-errors"
exclude-result-prefixes="xs"
version="3.0">
<xsl:template match="/">
<xsl:stream href="books.xml">
<xsl:iterate select="catalog">
<xsl:result-document href="out.xml" omit-xml-declaration="no" indent="yes">
<xsl:copy>
<xsl:for-each select="product">
<xsl:try>
<xsl:copy-of select="number"/>
<xsl:catch>
<xsl:result-document href="error.txt">
<xsl:message>Element number not given in <xsl:value-of select="product/#dept"/></xsl:message>
<error code="{$err:code}" message="{$err:description}"/>
</xsl:result-document>
</xsl:catch>
</xsl:try>
</xsl:for-each>
</xsl:copy>
</xsl:result-document>
</xsl:iterate>
</xsl:stream>
</xsl:template>
</xsl:stylesheet>
My requirement is how can I uses try/catch when not find the number element then make a file with error.

Answer 1

Try this to generate error message in log file by taking the value in variable in then check some conditon:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:err="http://www.w3.org/2005/xqt-errors"
exclude-result-prefixes="xs"
version="3.0">
<xsl:template match="/">
<xsl:stream href="books.xml">
<xsl:iterate select="catalog">
<xsl:result-document href="out.xml" omit-xml-declaration="no" indent="yes">
<xsl:copy>
<xsl:for-each select="product">
<xsl:variable name="num" select="if (number) then (number) else ('aaaa')"/>
<xsl:try>
<number>
<xsl:value-of select="format-number($num, '############')"/>
</number>
<xsl:catch>
<xsl:result-document href="error.log" omit-xml-declaration="yes">
<xsl:value-of select="concat(' Element number not given in ', #dept)"/>
<xsl:value-of select="concat(' Error code: ', $err:code, ' and Error Desc is: ', $err:description)"/>
</xsl:result-document>
</xsl:catch>
</xsl:try>
</xsl:for-each>
</xsl:copy>
</xsl:result-document>
</xsl:iterate>
</xsl:stream>
</xsl:template>
</xsl:stylesheet>