Find a Element by attribute in a XML Document in Java and get value of another attribute in the same element

Question

I was tasked to convert some of my Python code to Java.

In the original there is a lot of operations like this:

name = element.find('*/DIAttribute[@name="ui_display_name"]').attrib['value']

Where element is a lxml.etree.Element object.

In Java I’m doing this to get the same value:

XPath xPath =  XPathFactory.newInstance().newXPath();
NodeList nodesName = (NodeList) xPath.evalute("DIAttribute[@name='ui_display_name']", element, XPathConstants.NODE);
if nodesName.getLength() > 0 {
    Node node = nodesName.item(0);
    name = node.getAttributes().getNamedItem("value");
}

I’m doing it right? There is a better way of doing this? I’m using the org.w3c.dom objects, and the powers that be forbid me of using other XML libraries.

Thanks!

Asked By: João Bordignon

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Source

Answer 1

Passing XPathConstants.NODE does not cause evaluate to return a NodeList, it causes the method to return a single Node. The class documentation describes exactly what type of object will be returned for each XPathConstant field.

Node node = (Node) xPath.evaluate("DIAttribute[@name='ui_display_name']", element, XPathConstants.NODE);

Attributes are document nodes too, so you can simplify the code into a single XPath expression:

Node node = (Node) xPath.evaluate("DIAttribute[@name='ui_display_name']/@value", element, XPathConstants.NODE);
String name = node.getNodeValue();

Since you just want the string value of the node, you can use the two-argument evaluate method instead, omitting the XPathConstants value:

String name = xPath.evaluate("DIAttribute[@name='ui_display_name']/@value", element);

That will only find DIAttribute elements which are direct children of element. If you want to search all DIAttribute descendants at all levels below element, use .// in your XPath expression:

String name = xPath.evaluate(".//DIAttribute[@name='ui_display_name']/@value", element);

Answered By: VGR

Find a Element by attribute in a XML Document in Java and get value of another attribute in the same element

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