Why "xsl:if test" don't work on Barcode4j plugin

Question

Good afternoon at all members! I have a problem with testing the value of barcode. First, I'll show you the xsl and the xml code, then I'll explain the trouble. Xsl code:

<fo:table-cell  font-size="7" padding="0.5mm" border-width="0.2mm" border-style="transparent">
                                    <fo:block>
                                        <xsl:if test="gsmsg/barcode">
                                            <fo:block>
                                              <fo:instream-foreign-object>
                                              <xsl:variable name="Barcod">
                                              <xsl:value-of select="gsmsg/barcode"/>
                                              </xsl:variable>
                                                        <barcode:barcode xmlns:barcode="http://barcode4j.krysalis.org/ns"
                                                         message="{$Barcod}" orientation="0">
                                                        <barcode:code128>
                                                    <barcode:height>8mm</barcode:height>
                                                </barcode:code128>
                                            </barcode:barcode>
                                              </fo:instream-foreign-object>
                                            </fo:block>
                                        </xsl:if>
                                    </fo:block>
                                </fo:table-cell>

Xml source code:

<gsmsg xmlns="">
    <IdentificativoSdI>169077607</IdentificativoSdI>
    <NomeFile>IT01942890995.xml</NomeFile>
    <Formato>FPR12</Formato>
    <MessageId>1185389295</MessageId>
    <TentativiInvio>1</TentativiInvio>
    <Lotto>405</Lotto>
    <attpass>P</attpass>
    <Versione>0.7</Versione>
    <TipoMsg>DO</TipoMsg>
    <barcode/>
    <note/>
</gsmsg>

Value of barcode is empty. In terms of teory <xsl:if test="gsmsg/barcode"> must verify if there's a value, and if not , fop don't read the Barcode4j plugin. In my case, <xsl:if test="gsmsg/barcode"> doesen't work, because continue to read the Barcode4j plugin and the print crashes due to barcode's "message" parameter cannot be empty. Why xsl:if doesen't work in my case? Please help me,

Best regards, Marco

Answer 1

In terms of theory,

<xsl:if test="gsmsg/barcode">

tests for the existence of the barcode element.

If you want to test for the existence of a text value, do:

<xsl:if test="string(gsmsg/barcode)">

or:

<xsl:if test="gsmsg/barcode/text()">