CODEWITHSUNDEEP
java
BKK
BKK

Reputation: 1199

Validate XML element tag

I am having a XML file like 

<parent>
  <child1>
   <child2>
     <name>name</name>
     <value>
     <item>value></item>
    </value>
  </child2>
 </child1>
  <child1>
   <value>
     <item>value></item>
    </value>
 </child1>
</parent>

Here i need to check, whether child2 node is missing or not.

My java code is like

File xmlfile = new File ("sample.xml");
DocumentBuilderFactory dbfaFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder documentBuilder = dbfaFactory.newDocumentBuilder();
Document doc = documentBuilder.parse(xmlfile);
NodeList child1= doc.getElementsByTagName("child1");
for( int i=0; i<child1.getLength(); i++)
{
NodeList child1= doc.getElementsByTagName("child1");
if(!doc.getElementsByTagName("child2").equals(null))
{
System.out.println("Not Equal to null");

                else
                {
                    System.out.println("Equal to null");
                }
}

But every time i am getting Not Equal to null, even though child2 node is missing in the XML.

Here child2 is missing

<child1>
   <value>
     <item>value></item>
    </value>
 </child1>

Thanks.

Upvotes: 0

Views: 1483

Answers (2)

davidfmatheson
davidfmatheson

Reputation: 3567

You might find XPath is well-suited for this task:

    try {
        DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
        documentBuilderFactory.setNamespaceAware(true);
        DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
        Document document = documentBuilder.parse(new File("sample.xml"));

        XPathFactory xPathFactory = XPathFactory.newInstance();
        XPath xPath = xPathFactory.newXPath();
        XPathExpression xPathExpression = xPath.compile("/parent/child1/child2");

        NodeList nodeList = (NodeList) xPathExpression.evaluate(document, XPathConstants.NODESET);

        for (int i = 0; i < nodeList.getLength(); i++) {
            Node node = nodeList.item(i);
            System.out.println(node.getNodeName());
        }

If child2 is there, then nodeList.getLength() will equal one (or the number of child2 elements there are under child1), otherwise it will be zero.

If you want all the instances where child1 has a child that is not child2 you can use:

/parent/child1/*[not(self::child2)]

as your XPath expression. If you only want to count the number of times that child1 has any children that are not child2 then you can use:

/parent/child1/*[not(self::child2)][1]

Upvotes: 0

JBert
JBert

Reputation: 3390

This code cannot work: doc.getElementsByTagName("child2") traverses the whole XML, i.e. it returns ANY child2 it can find.

Either try using child1.getElementsByTagName("child2"), or consider using a "sane" XML library. XOM for example has a function getChildElements(String name) which works in the way you would expect.

EDIT: As Jenson noted, you might run into NullPointerExceptions with that null check clause, use child1.getElementsByTagName("child2") != null instead.

Upvotes: 1

Related Questions