question Re: How do you declare a namespace for proper XPath use within EvaluateXPath in Archives of Support Questions (Read Only)

How do you declare a namespace for proper XPath use within EvaluateXPath

dave_sargrad — Sun, 18 Aug 2019 05:12:27 GMT

I have made some progress understanding and using EvaluateXPath.

I've been able, for example, to generate a flow file with the content

<?xml version="1.0" encoding="UTF-8"?><bookstore>  <book>    <title lang="en">Harry Potter</title>    <author>J K. Rowling</author>    <year>2005</year>    <price>29.99</price>  </book></bookstore>

and match this using the following (notice //year as the XPath)

However if I have a namespace in the XML

, then I have a problem (notice //ns8:textNOTAM as the XPath)

Re: How do you declare a namespace for proper XPath use within EvaluateXPath

dave_sargrad — Thu, 27 Sep 2018 01:13:38 GMT

Oh No!! It looks like there has been an issue outstanding for over 2 years...

Is there no way for me to use EvaluateXPath on XML that contains namespaces?

https://community.hortonworks.com/questions/45869/nifi-xml-namespace.html

https://issues.apache.org/jira/browse/NIFI-1023

Re: How do you declare a namespace for proper XPath use within EvaluateXPath

dave_sargrad — Thu, 27 Sep 2018 01:43:33 GMT

Omg.. that worked!!

The XPath I had to use (within the EvaluateXPath processor configuration) was as follows:

//*[local-name()='textNOTAM']

This is stuff that should live in a NIFI user manual someplace.

Re: How do you declare a namespace for proper XPath use within EvaluateXPath

dave_sargrad — Thu, 27 Sep 2018 04:52:11 GMT

Also an interesting stackoverflow link

https://stackoverflow.com/questions/6390339/how-to-query-xml-using-namespaces-in-java-with-xpath

it seems that maybe there is a workaround that i can use with evaluatexpath it might look something like the following

/*[local-name()='workbook']/*[local-name()='sheets']/*[local-name()='sheet'][1]

Re: How do you declare a namespace for proper XPath use within EvaluateXPath

dave_sargrad — Sun, 18 Aug 2019 05:12:08 GMT

I've found several interesting stack overflow articles.. including the following:

https://stackoverflow.com/questions/3931817/xpath-expression-from-xml-with-namespace-prefix

I should be able to match the book in the following with a simple //bk:book

<bk:bookstore xmlns:bk="urn:xmlns:25hoursaday-com:bookstore">
 <bk:book> 
    <bk:title>Lord of the Rings</bk:title> 
    <bk:author>J.R.R. Tolkien</bk:author>
    <inv:inventory status="in-stock" isbn="0345340426" 
        xmlns:inv="urn:xmlns:25hoursaday-com:inventory-tracking" />
 </bk:book> 
</bk:bookstore>

Somehow NIFI needs to let me register the namespace.

I've also tried out online xpath formatters, and they have allowed me to simply add the namespace to the xpath as follows

https://www.freeformatter.com/xpath-tester.html#ad-output

matches //bk:book

Re: How do you declare a namespace for proper XPath use within EvaluateXPath

dave_sargrad — Fri, 28 Sep 2018 10:19:51 GMT

Since I've gotten past this, but i'd like others to understand it as well, i've dug a tiny bit more to understand this "local-name" magic.

Several links of interest

https://examples.javacodegeeks.com/core-java/xml/xpath/xpath-local-name-example/

https://developer.mozilla.org/en-US/docs/Web/XPath/Functions/local-name

https://docs.oracle.com/cd/E35413_01/doc.722/e35419/dev_xpath_functions.htm#autoId6

http://www.codesimplify.com/java/java-xpath-ignore-namespace-example/

Enjoy

Re: How do you declare a namespace for proper XPath use within EvaluateXPath

nverwer — Tue, 16 Jul 2019 19:56:40 GMT

Instead of using local-name, you can also do this:

//*:textNOTAM

This has a wildcard for the namespace prefix, and the element name in the place where you would expect it.

This tends to be more readable for longer XPaths like

/*:feed/*:entry/*:title

Re: How do you declare a namespace for proper XPath use within EvaluateXPath

dave_sargrad — Tue, 16 Jul 2019 23:23:54 GMT

Thanks @Nico Verwer. I'll give that a shot, and will be sure to accept your response as an answer, once I verify.

Re: How do you declare a namespace for proper XPath use within EvaluateXPath

Svsio — Fri, 30 Sep 2022 21:35:52 GMT

@nverwer wrote:
Instead of using local-name, you can also do this:
//*:textNOTAM
This has a wildcard for the namespace prefix, and the element name in the place where you would expect it.
This tends to be more readable for longer XPaths like
//*:feed//*:entry//*:title

This info was hard to find. @nverwer thanks. Saved my day!