如何在Java中使用XPath查询选择元素的属性值并将其放入字符串中？

Question

I am pretty new in XPath query into Java and I have the following problem:

I have a org.jdom.Document documentXML variable that contains the following XML content:

<?xml version="1.0" encoding="UTF-8"?>
<root>
  <status>
    <id>0</id>
    <message>Operazione conclusa con successo</message>
  </status>
  <drivers>
    <drive id="MyID">
      <propery1 />
      <property2 />
      <property3 />
      <property4>0</property4>
      <sproperty5>104857600</property5>
      <property6 />
    </drive>
  </drivers>
</root>

I have to select the value inside the id attribute and put it into a String (so I have to put the "MyID" value inside a String)

In Java I have to something like this (that don't work):

org.jdom.output.XMLOutputter xmlOutputterCDATAContent = new org.jdom.output.XMLOutputter(org.jdom.output.Format.getPrettyFormat());

xmlOutputter.output(documentXML, System.out);

xPath = XPath.newInstance("/root/drivers/drive/@id");
objectElement = (Element) xPath.selectSingleNode(documentXML);
driveId = objectElement.getValue();
System.out.println("ID " + objectElement.getValue() + " /ID");

So, as you can see the documentXML variable contains the previous XML code

I create an XPath query to access to the value of id attribute of the drive node, then I try to put this value into the driveId (that is a String object)

But in this way can't work and when I run this code I obtain the following error message:

java.lang.ClassCastException: org.jdom.Attribute cannot be cast to org.jdom.Element

What is the problem? What am I missing? How can I solve?

Tnx

Andrea

Answer 1

Like you already mentioned, the id you want to get is an .

Hence, you just have to change your cast from org.jdom.Element to org.jdom.Attribute . Then you can call driveId.getValue() to get the String value for id.

Answer 2

您可以使用jcabi-xml并在一行中完成此操作：

String id = new XMLDocument(xml).xpath("/root/drivers/drive/@id").get(0);