Question

Please go easy on me , this is my first time using XPath 2.0 🙂

Given the following code :

import net.sf.saxon.expr.Expression;
import net.sf.saxon.expr.StaticContext;
import net.sf.saxon.functions.CompileTimeFunction;
import net.sf.saxon.sort.Reverser;
import net.sf.saxon.trans.XPathException;

public class MyReverse extends CompileTimeFunction {

    public Expression simplify(StaticContext env) throws XPathException {
        Reverser a = new Reverser(argument[0]);
        return a.simplify(env);
    }

}

I want to reverse the query :

String query = "inventory/book/chapter[3]/preceding-sibling::chapter//title";
Object myQuery= xpath.evaluate(query,doc,XPathConstants.NODESET);

for my XML file (I can attach the XML file if you wish ,so please say so if it’s indeed required!)

Now from my understanding if I do this :

MyReverse rev = new MyReverse();

then if I try to use the method evaluateAsString like this : rev.evaluateAsString(arg0)
then arg0 should be a XPathContext object .

How can I use my query with the above method ?

Regards

EDIT 1:

In the example that dear Mr. @Dimitre Novatchev wrote , what is needed is all the nodes from node X , to the upper side of the document.

However , if one of X's siblings , has children , then I need to present the sibling and only then his (the sibling’s) children (and after that move on to the next sibling , and the same all over again) , and not the child of the sibling & only then – the sibling .

I’m sorry for not mentioning & explaining this earlier

thanks again 🙂

Answer 1

Just evaluate this XPath 2.0 expression:

reverse(/inventory/book/chapter[3]/preceding-sibling::chapter//title)

Here is an XSLT -based verification:

<xsl:stylesheet version="2.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="/">
     <xsl:sequence select=
     "reverse(/inventory/book/chapter[3]/preceding-sibling::chapter//title)
     "/>
 </xsl:template>
</xsl:stylesheet>

When this transformation is applied on the following XML document (taken from your previous question):

<inventory>
    <book num="myBook1">
        <title>Lindsy Boxer</title>
        <author>James Patterson</author>
        <publisher>LittleBig</publisher>
        <price>18.21</price>
        <chapter>
            <title>Alex Cross Is Back - Chapter A</title>
            <paragraph>
                    This is the 
                <emph>first</emph> paragraph.
                <image file="alexCrossImage.gif"/>
                    afetr image...
            </paragraph>
            <paragraph>
                    This is the 
                <emph>second</emph> paragraph.
                <image file="alexCrossImageAnother.gif"/>
                    afetr image...
            </paragraph>
        </chapter>
        <chapter>
            <title>Along Came A Spider - Chapter B</title>
            <section>
                <title>Along Came A Spider - Chapter B - section 1</title>
                <paragraph>
                        This is the 
                    <emph>first</emph>paragraph for chapter TWO section ONE.
                    <image file="Chapter_B_firstParagraphImage.gif"/>
                        afetr image...
                </paragraph>
                <paragraph>
                        This is the 
                    <emph>second</emph> paragraph for chapter TWO section ONE.
                    <image file="Chapter_B_secondParagraphImage.gif"/>
                        afetr image...
                </paragraph>
            </section>
        </chapter>
        <chapter>
            <title>Chapter C</title>
            <paragraph>
                    This chapter has no images and only one paragraph
            </paragraph>
        </chapter>
    </book>
    <book num="myBook2">
        <title>Jack Reacher Series</title>
        <author>Lee Child</author>
        <author>Jonny White</author>
        <publisher>Pocket</publisher>
        <price>5.99</price>
        <chapter>
            <title>Jack Reacher - Chapter ONE</title>
        </chapter>
        <chapter>
            <title>Jack Reacher - Chapter TWO</title>
            <paragraph>
                    This is the 
                <emph>second</emph> paragraph of SECOND book chapter TWO.
                <image file="Jack_Reacher_Picture_Top_Sniper_US_Army.gif"/>
                    afetr image...
            </paragraph>
        </chapter>
    </book>
    <book num="myBook3">
        <title>Alex Cross - Double Cross</title>
        <author>James Patterson</author>
        <publisher>Spectra</publisher>
        <price>17.30</price>
        <chapter>
            <title>Alex Cross - Double Cross - Chapter A</title>
        </chapter>
    </book>
</inventory>

the above XPath expression is evaluated and the resulting sequence of nodes is copied to the output:

<title>Along Came A Spider - Chapter B - section 1</title>
<title>Along Came A Spider - Chapter B</title>
<title>Alex Cross Is Back - Chapter A</title>

As we can see, the sequence contains the wanted elements and in reverse-document order — exactly as requested.

As for how to evaluate an XPath expression with Saxon 9.x, read the appropriate documentation: http://www.saxonica.com/documentation/xpath-api/s9api-xpath.xml which has a pointer to a fully working code example.

UPDATE:

In a comment the OP has indicated that he needs the chapter elements in reverse document order, but their title elements in document order.

To avhieve this, use:

reverse(/inventory/book/chapter[3]/preceding-sibling::chapter)//title