[xml] How to check if an element exists in the xml using xpath?

Below is my element hierarchy. How to check (using xpath) that AttachedXml element is present under CreditReport of Primary Consumer

<Consumers xmlns="http://xml.mycompany.com/XMLSchema">
       <Consumer subjectIdentifier="Primary">
          <DataSources>
               <Credit>
                   <CreditReport>
                      <AttachedXml><![CDATA[ blah blah]]>

The Saxon documentation, though a little unclear, seems to suggest that the JAXP XPath API will return false when evaluating an XPath expression if no matching nodes are found.

This IBM article mentions a return value of null when no nodes are matched.

You might need to play around with the return types a bit based on this API, but the basic idea is that you just run a normal XPath and check whether the result is a node / false / null / etc.

XPathFactory xpathFactory = XPathFactory.newInstance(NamespaceConstant.OBJECT_MODEL_SAXON);
XPath xpath = xpathFactory.newXPath();
XPathExpression expr = xpath.compile("/Consumers/Consumer/DataSources/Credit/CreditReport/AttachedXml");
Object result = expr.evaluate(doc, XPathConstants.NODE);

if ( result == null ) {
    // do something
}

If boolean() is not available (the tool I'm using does not) one way to achieve it is:

//SELECT[@id='xpto']/OPTION[not(not(@selected))]

In this case, within the /OPTION, one of the options is the selected one. The "selected" does not have a value... it just exists, while the other OPTION do not have "selected". This achieves the objective.

take look at my example

<tocheading language="EN"> 
     <subj-group> 
         <subject>Editors Choice</subject> 
         <subject>creative common</subject> 
     </subj-group> 
</tocheading> 

now how to check if creative common is exist

tocheading/subj-group/subject/text() = 'creative common'

hope this help you

Use:

boolean(/*/*[@subjectIdentifier="Primary"]/*/*/*/*
                           [name()='AttachedXml' 
                          and 
                            namespace-uri()='http://xml.mycompany.com/XMLSchema'
                           ]
       )

Normally when you try to select a node using xpath your xpath-engine will return null or equivalent if the node doesn't exists.

xpath: "/Consumers/Consumer/DataSources/Credit/CreditReport/AttachedXml"

If your using xsl check out this question for an answer:

xpath find if node exists