Java – XPATH select only first level children

javaxmlxpath

I have the fowoling xml :

  <workflow URI=""> 
  <output ID="" URI="#out1"/>  
  <input ID="sessionToken" URI="#sessionToken"/>  
  <services> 
    <sequence> 
      <service URI=""> 
        <input ID="" URI=""/>  
        <input URI="" value=""/>  
        <output ID="" URI=""/> 
      </service> 
    </sequence> 
  </services> 
</workflow>

I want to select only the first level children of the workflow node and exclude from this selection the services node, so in my case I would only want

 <output ID="" URI="#out1"/>  
 <input ID="sessionToken" URI="#sessionToken"/>

this two nodes selected, and I want to use XPATH in java for this. The additional requirments is that the selected node must have the URI parameter.

I have tried this :

XPathExpression expr = xpath.compile("//workflow[@URI='" + oldUrlValue.getNodeValue() + "'] | //workflow//*[not(local-name() = 'services') and @URI]");

but I get backall the nodes with URI parameters instead only the main workflow node and the first two children.

I have tried this

Best Answer

It isn't clear what you mean by 'first level children' here, because services is located at the same level as output and input elements. If you mean to return direct child of workflow that do not have any further child element, then you can use the following XPath expression :

//workflow/*[not(*)]

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How to select the first element with a specific attribute using XPath

Use:

(/bookstore/book[@location='US'])[1]

This will first get the book elements with the location attribute equal to 'US'. Then it will select the first node from that set. Note the use of parentheses, which are required by some implementations.

Note, this is not the same as /bookstore/book[1][@location='US'] unless the first element also happens to have that location attribute.

Java – How to read XML using XPath in Java

You need something along the lines of this:

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(<uri_as_string>);
XPathFactory xPathfactory = XPathFactory.newInstance();
XPath xpath = xPathfactory.newXPath();
XPathExpression expr = xpath.compile(<xpath_expression>);

Then you call expr.evaluate() passing in the document defined in that code and the return type you are expecting, and cast the result to the object type of the result.

If you need help with a specific XPath expressions, you should probably ask it as separate questions (unless that was your question in the first place here - I understood your question to be how to use the API in Java).

Edit: (Response to comment): This XPath expression will get you the text of the first URL element under PowerBuilder:

/howto/topic[@name='PowerBuilder']/url/text()

This will get you the second:

/howto/topic[@name='PowerBuilder']/url[2]/text()

You get that with this code:

expr.evaluate(doc, XPathConstants.STRING);

If you don't know how many URLs are in a given node, then you should rather do something like this:

XPathExpression expr = xpath.compile("/howto/topic[@name='PowerBuilder']/url");
NodeList nl = (NodeList) expr.evaluate(doc, XPathConstants.NODESET);

And then loop over the NodeList.

Best Answer

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