Is it possible to ignore/skip nodes while parsing xml in Java

Question

I'm trying to remove SOAP and ns2 nodes from this XML :

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"       SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"&gt;
<SOAP-ENV:Body>
<ns2:createCustomer>
    <Customer>
        <CustomerId/>
        <names>
            <firstName>fName</firstName>
            <lastName>lName</lastName>
            <middleName>nName</middleName>
            <nickName/>
            </names>
        <addressList>
            <address>
                <streetInfo>
                    <houseNumber>22</houseNumber>
                    <baseName>Street base name</baseName>
                    <district>kewl district</district>
                    </streetInfo>
                <zipcode>22231</zipcode>
                <state>xxx</state>
                <country>xxxz</country>
                <primary>true</primary>
                </address>
            </addressList>
        <SSN>561381</SSN>
        <phone>
            <homePhone>123123123</homePhone>
            <officePhone/>
            <homePhone>21319414</homePhone>
            </phone>
        <preferred>true</preferred>
        </Customer>
        </ns2:createCustomer>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Is this possible before this :

Document doc = parser.parse(xmlFile); 
NodeList startlist = doc.getChildNodes();

I tried to read this as String then writing it back to the XML file like this :

private void preParsing(String fileName,String ...tags) {

        try {

            BufferedReader br = new BufferedReader(new FileReader(new File(fileName)));
            StringBuilder sb = new StringBuilder();
            String line;

            while ((line = br.readLine()) != null) {
                for (String string : tags) {
                    if(!line.contains(string)){
                        sb.append(line);
                        sb.append("\n");
                    }
                }
            }           

            System.out.println(sb.toString());

            br.close();

        } catch (IOException e) {
            System.err.println("Error occured: " + e.getMessage());
        }

    }

It worked if I ignore only one tag like :

preParsing("src/main/resources/test.xml", "SOAP");

But it didn't work when I pass more than one tag argument to ignore/remove from file. I'm sure there is more elegant way of doing this I just can't think of any.

Answer 1

Your best bet is to load the document normally, and use XPath to get at the parts that you want.

There is some good info at http://stackoverflow.com/questions/2811001/how-to-read-xml-using-xpath-in-java

Answer 2

You could use a StAX filter:

class MyFilter implements EventFilter {
  private final List<String> filtered = Arrays.asList("SOAP-ENV:Envelope",
      "SOAP-ENV:Body", "ns2:createCustomer");

  @Override
  public boolean accept(XMLEvent event) {
    if (event.isStartElement())
      for (String elementName : filtered)
        if (event.asStartElement().getName().getLocalPart().equals(
            elementName))
          return false;
    if (event.isEndElement())
      for (String elementName : filtered)
        if (event.asEndElement().getName().getLocalPart().equals(
            elementName))
          return false;
    return true;
  }
}

Usage:

DOMResult result = new DOMResult();
XMLInputFactory xmlInputFactory = XMLInputFactory.newInstance();
xmlInputFactory.setProperty(XMLInputFactory.IS_NAMESPACE_AWARE, false);
XMLEventReader reader = xmlInputFactory
    .createXMLEventReader(new StreamSource(new File("soap.xml")));
reader = xmlInputFactory.createFilteredReader(reader, new MyFilter());
TransformerFactory transFactory = TransformerFactory.newInstance();
Transformer transformer = transFactory.newTransformer();
transformer.transform(new StAXSource(reader), result);
Document document = (Document) result.getNode();

FYI: SOAP-ENV and ns2 are not elements; they are namespace prefixes. The document is malformed - there is missing namespace declarations & the above code is not what I would write for a valid namespaced document.

Answer 3

A common approach to manipulate XML documents, is to use XSLT. This e.g. allow you to write filters that can remove any tag in a specific namespace, and much more.

The XSLT language is quite different from Java, but there is a XSLT processor (check the Templates and Transformer classes) in Java since 1.4, so it is well supported.