How can i get XPath of the XML Node using Java API without DTD and XSD

[saravanan periasamy]

Dear All,

I have a java program which will iterate all nodes from xml document.But i want to return/display each node's XPath with out using any DTD and XSD file standard.

Please help me!.

Thanks in Advance,
Saravanan.P

[Ulf Dittmer]

Usually you'd use XPath to get a node from an XML/DOM document, not the other way around.

If you're using SAX, you could create XPath expressions something like this:

    
List<String> elements = new ArrayList()
 
inside of startElement method:
    elements.add(localName)
 
inside of endElement method:
    elements.remove(elements.size()-1)
 
String getCurrentXPath() {
    String str = "//"
    boolean first = true;
    for (String s : elements) {
        if (first)
            str = str + s
        else
            str = str + "/" + s
        first = false
    }
    return str
}

[saravanan periasamy]

Dear Ulf Dittmer,

Ok.I am following your idea now.But i have a duplicate nodes for particular node in the xml document.How can i get the exact path of the XPath of the node.

Thanks,
Saravanan

[Ulf Dittmer]

In that case you have to count the nodes, and add an "[...]" part to the XPath to select the proper one (after the element name).

[saravanan periasamy]

Thanks Ulf Dittmer,

I will try that.

Regards,
Saravanan.P

[Ulf Dittmer]

That's actually a fun little problem. I took a first stab at it here. As noted on that page, it's not perfect, but adequate for certain kinds of XML documents.

[saravanan periasamy]

Ulf Dittmer,

Its looking good,I think it may fit for my requirement.Let me try that.


Thanks a lot,
Saravanan.P

[saravanan periasamy]

hi,
i was able to get the xpath of the nodes.But it displays the value as zero for all the nodes.

This is the result i am getting.

path /C:/Documents/
Tag Name catalog
Tag Name journal
Tag Name article
Tag Name title
XPath //catalog[0]/journal[0]/article[0]/title[0]
Tag Name author
XPath //catalog[0]/journal[0]/article[0]/author[0]
XPath //catalog[0]/journal[0]/article[0]
XPath //catalog[0]/journal[0]
Tag Name books
Tag Name article
Tag Name title
XPath //catalog[0]/books[0]/article[0]/title[0]
Tag Name author
XPath //catalog[0]/books[0]/article[0]/author[0]
XPath //catalog[0]/books[0]/article[0]
XPath //catalog[0]/books[0]
Tag Name journal
Tag Name article
Tag Name title
XPath //catalog[0]/journal[0]/article[0]/title[0]
Tag Name author
XPath //catalog[0]/journal[0]/article[0]/author[0]
XPath //catalog[0]/journal[0]/article[0]
XPath //catalog[0]/journal[0]
Tag Name book
Tag Name article
Tag Name title
XPath //catalog[0]/book[0]/article[0]/title[0]
Tag Name author
XPath //catalog[0]/book[0]/article[0]/author[0]
XPath //catalog[0]/book[0]/article[0]
XPath //catalog[0]/book[0]
Tag Name journal
Tag Name article
Tag Name title
XPath //catalog[0]/journal[0]/article[0]/title[0]
Tag Name author
XPath //catalog[0]/journal[0]/article[0]/author[0]
XPath //catalog[0]/journal[0]/article[0]
XPath //catalog[0]/journal[0]
XPath //catalog[0]

The xml file used is:

<?xml version="1.0" encoding="utf-8"?>
<catalog>
<journal title="Oracle Magazine" publisher="Oracle Publishing" edition="July-August 2005">
<article section="Technology">
<title>Tuning Undo Tablespace</title>
<author>Kimberly Floss</author>
</article></journal>
<books title="Oracle Magazine" publisher="Oracle Publishing" edition="July-August 2005">
<article section="Developer">
<title>Using PHP 5 with Oracle XML DB</title>
<author>Yuli Vasiliev</author>
</article></books>
<journal title="Oracle Magazine" publisher="Oracle Publishing" edition="July-August 2005">
<article section="Developer">
<title>Using PHP 5 with Oracle XML DB</title>
<author>Yuli Vasiliev</author>
</article></journal>
<book title="Oracle Magazine" publisher="Oracle Publishing" edition="July-August 2005">
<article section="Developer">
<title>Using PHP 5 with Oracle XML DB</title>
<author>Yuli Vasiliev</author></article>
</book><journal title="Oracle Magazine" publisher="Oracle Publishing" edition="July-August 2005">
<article section="Developer">
<title>Using PHP 5 with Oracle XML DB</title>
<author>Yuli Vasiliev</author>
</article></journal></catalog>


Could you please help me on this.

[saravanan periasamy]

hi Ulf Dittmer,

Could you please help on the above issue.

Thanks in Advance,
Saravanan.

[Ulf Dittmer]

That's what the comment at the beginning of the code means - it will not work if the tags are not consecutive. Since between the first and second "journal" there's a "book" element, the counter will be reset. Fixing that is left as an exercise to the reader :-)

[saravanan periasamy]

ok let me try..thank you :-)

[Ulf Dittmer]

I have updated the sample code to deal with part of the problem. It now works with the example you posted. But it's still not perfect; see the code for an example where it fails.
[ July 28, 2007: Message edited by: Ulf Dittmer ]

[Aditi Gandy]

I am also getting same error. I have copied the sample code. Every thing is working fine except the error mentioned in at the beggining of the program....

Can any one please help me?

Please

[Planet Bob]

To fix this issue, store the count for XPath itself rather than the tag.

ALSO NOTE that XPath has "1" as starting index, not the ZERO.

public class SAXCreateXPath extends DefaultHandler {

    // map of all encountered tags and their running count
    private Map<String, Integer> xPathCount = new HashMap<String, Integer>();
    // keep track of the succession of elements
    private Stack<String> tags = new Stack<String>();;

    /**
     * Construct the XPath expression
     */
    private String getCurrentXPath(String child) {
        String str = "//";
        boolean first = true;
        for (String tag : tags) {
            if (first)
                str = str + tag;
            else
                str = str + "/" + tag;
            str += "[" + xPathCount.get(str) + "]";
            first = false;
        }
        if (child != null) {
            str = str + (first ? "" : "/") + child;
        }
        return str;
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        String xPath = getCurrentXPath(localName);
        int count = (xPathCount.get(xPath) == null) ? 0 : xPathCount.get(xPath);
        xPathCount.put(xPath, 1 + count);
        tags.push(localName);

        System.out.println(getCurrentXPath());
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
        tags.pop();
    }
}