Develop Reference

Liferay 7 Extending EditableFragmentEntryProcessor

I want to extend functionality of EditableFragmentEntryProcessor in Liferay 7.4 (<lfr-editable> tags in fragments) by searching in text syntaxes like {user.name} and replacing it with value from response from my external API.
e.x.
I type something like
This is super fragment and you are {user.name}.
And result should be
This is super fragment and you are Steven.
I achieve that with creating my own FragmentEntryProcessor, but I did this by putting fragment configuration variable in my custom tag
<my-data-api> ${configuration.testVariable} </my-data-api>
I tried something like this before
<my-data-api>
<lfr-editable id="some-id" type="text">
some text to edit
</lfr-editable>
</my-data-api>
And it doesn't work (and I know why).
So I want to get something like this. Appreciate any help or hints.
EDIT:
Here my custom FragmentEntryProcessor:
package com.example.fragmentEntryProcessorTest.portlet;
import com.example.test.api.api.TestPortletApi;
import com.liferay.fragment.exception.FragmentEntryContentException;
import com.liferay.fragment.model.FragmentEntryLink;
import com.liferay.fragment.processor.FragmentEntryProcessor;
import com.liferay.fragment.processor.FragmentEntryProcessorContext;
import com.liferay.portal.kernel.exception.PortalException;
import com.liferay.portal.kernel.util.Validator;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Reference;
import java.io.IOException;
/**
* #author kabatk
*/
#Component(
immediate = true, property = "fragment.entry.processor.priority:Integer=100",
service = FragmentEntryProcessor.class
)
public class FragmentEntryProcessorApiDataCopy implements FragmentEntryProcessor {
private static final String _TAG = "my-data-api";
#Reference
private TestPortletApi _api;
#Override
public String processFragmentEntryLinkHTML(
FragmentEntryLink fragmentEntryLink, String html,
FragmentEntryProcessorContext fragmentEntryProcessorContext)
throws PortalException {
Document document = _getDocument(html);
Elements elements = document.getElementsByTag(_TAG);
elements.forEach(
element -> {
String text = element.text();
String attrValue = element.attr("dataType");
String classValues = element.attr("classes");
Element myElement = null;
String result;
try {
result = _api.changeContent(text);
} catch (IOException e) {
e.printStackTrace();
result = "";
}
if(attrValue.equals("img")){
myElement = document.createElement("img");
myElement.attr("class", classValues);
myElement.attr("src", result);
}else if(attrValue.equals("text")){
myElement = document.createElement("div");
myElement.attr("class", classValues);
myElement.html(result);
}
if(myElement != null)
element.replaceWith(myElement);
else
element.replaceWith(
document.createElement("div").text("Error")
);
});
Element bodyElement = document.body();
return bodyElement.html();
}
#Override
public void validateFragmentEntryHTML(String html, String configuration)
throws PortalException {
Document document = _getDocument(html);
Elements elements = document.getElementsByTag(_TAG);
for (Element element : elements) {
if (Validator.isNull(element.attr("dataType"))) {
throw new FragmentEntryContentException("Missing 'dataType' attribute!");
}
}
}
private Document _getDocument(String html) {
Document document = Jsoup.parseBodyFragment(html);
Document.OutputSettings outputSettings = new Document.OutputSettings();
outputSettings.prettyPrint(false);
document.outputSettings(outputSettings);
return document;
}
}

JAVA & XML : com.sun.org.apache.xpath.internal.XPathException: Can not convert #STRING to a NodeList

I am writing a java function that is parsing an xml element & extracting the given xpath expression. Below is the function :
public static Node getDataNode(Element payload, final HashMap<String, String> namespaces, String xpathStr) {
Node node = null;
try {
// Create a namespace context based on the namespaces passed in.
NamespaceContext ctx = new NamespaceContext() {
public String getNamespaceURI(String prefix) {
return namespaces.get(prefix);
}
public Iterator getPrefixes(String val) {
return null;
}
public String getPrefix(String uri) {
return null;
}
};
XPathFactory xpathFact = XPathFactory.newInstance();
XPath xpath = xpathFact.newXPath();
xpath.setNamespaceContext(ctx);
XPathExpression expr = xpath.compile(xpathStr);
System.out.println("Got request to process node : " + payload.getLocalName() + " with " + xpathStr);
System.out.println(xpathStr + " has been compiled successfully.");
((XMLElement) payload).print(System.out);
node = (Node) expr.evaluate(payload, XPathConstants.NODE);
} catch (XPathExpressionException ex) {
ex.printStackTrace();
return null;
} catch (IOException io) {
io.printStackTrace();
return null;
}
return node;
}
Below is the logs for this part of function :
Got request to process node : Body with ".//soapenv:Body/pip:request"
".//soapenv:Body/pip:request" has been compiled successfully.
<soapenv:Body xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<pip:request xmlns:pip="http://xmlns.oracle.com/ServiceBusApplication/UserInterfaceTest/Pipeline">textContent</pip:request>
</soapenv:Body>
I have tried different xpath expression like //soapenv:Body/pip:request, .//soapenv:Body/pip:request but still i am getting the error :
com.sun.org.apache.xpath.internal.XPathException: Can not convert #STRING to a NodeList!
at com.sun.org.apache.xpath.internal.objects.XObject.error(XObject.java:711)
at com.sun.org.apache.xpath.internal.objects.XObject.nodeset(XObject.java:441)
at com.sun.org.apache.xpath.internal.jaxp.XPathExpressionImpl.getResultAsType(XPathExpressionImpl.java:357)
at com.sun.org.apache.xpath.internal.jaxp.XPathExpressionImpl.eval(XPathExpressionImpl.java:101)
at com.sun.org.apache.xpath.internal.jaxp.XPathExpressionImpl.evaluate(XPathExpressionImpl.java:182)
Please let me know what is wrong in the code.Appreciate your help in resolving the issue . Thanks.

Unable to reproduce. Tested with MCVE code below on Oracle JDK 1.5 and on Oracle JDK 9.
Only change made to getDataNode method is commenting out the ((XMLElement) payload).print(System.out) statement, since Oracle JDK doesn't have an XMLElement type.
Test
import java.io.StringReader;
import java.util.HashMap;
import java.util.Iterator;
import javax.xml.namespace.NamespaceContext;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.xml.sax.InputSource;
String xml = "<soapenv:Body xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope/\">\n" +
" <pip:request xmlns:pip=\"http://xmlns.oracle.com/ServiceBusApplication/UserInterfaceTest/Pipeline\">textContent</pip:request>\n" +
" </soapenv:Body>";
DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
domFactory.setNamespaceAware(true);
DocumentBuilder domBuilder = domFactory.newDocumentBuilder();
Document document = domBuilder.parse(new InputSource(new StringReader(xml)));
HashMap<String, String> namespaces = new HashMap<String, String>();
namespaces.put("soapenv", "http://schemas.xmlsoap.org/soap/envelope/");
namespaces.put("pip", "http://xmlns.oracle.com/ServiceBusApplication/UserInterfaceTest/Pipeline");
Node node = getDataNode(document.getDocumentElement(), namespaces, ".//soapenv:Body/pip:request");
System.out.println(node != null ? node.getTextContent() : null);
node = getDataNode(document.getDocumentElement(), namespaces, "/soapenv:Body/pip:request");
System.out.println(node != null ? node.getTextContent() : null);
node = getDataNode(document.getDocumentElement(), namespaces, ".//pip:request");
System.out.println(node != null ? node.getTextContent() : null);
Output
Got request to process node : Body with .//soapenv:Body/pip:request
.//soapenv:Body/pip:request has been compiled successfully.
null
Got request to process node : Body with /soapenv:Body/pip:request
/soapenv:Body/pip:request has been compiled successfully.
textContent
Got request to process node : Body with .//pip:request
.//pip:request has been compiled successfully.
textContent
As you can see, code runs fine, but the .//soapenv:Body/pip:request XPath is not correct for the given XML, since there is no <soapenv:Body> tag inside the given payload element.

Java Stax for Complex / Large XML

I have an XML file that is 4.2 GB! Obviously parsing the entire DOM is not practical. I have been looking at SAX and STAX to accomplish parsing this gigantic XML file. However all the examples I've seen are simple. The XML file I am dealing with has nested on nested on nested. There are areas where it goes 10+ levels.
I found this tutorial but not sure if its a viable solution.
http://www.javacodegeeks.com/2013/05/parsing-xml-using-dom-sax-and-stax-parser-in-java.html (botton example using STAX)
I'm not really sure how to handle nested objects.
I have created Java objects to mimic the structure of the XML. Here are a few, too many to display.
Record.java
public class Record implements Serializable {
String uid;
StaticData staticData;
DynamicData dynamicData;
}
Summary.java
public class Summary {
EWUID ewuid;
PubInfo pubInfo;
Titles titles;
Names names;
DocTypes docTypes;
Publishers publishers;
}
EWUID.java
public class EWUID {
String collId;
String edition;
}
PubInfo.java
public class PubInfo {
String coverDate;
String hasAbstract;
String issue;
String pubMonth;
String pubType;
String pubYear;
String sortDate;
String volume;
}
This is the code I've come up with so far.
public class TRWOSParser {
XMLEventReader eventReader;
XMLInputFactory inputFactory;
InputStream inputStream;
public TRWOSParser(String file) throws FileNotFoundException, XMLStreamException {
inputFactory = XMLInputFactory.newInstance();
inputStream = new FileInputStream(file);
eventReader = inputFactory.createXMLEventReader(inputStream);
}
public void parse() throws XMLStreamException{
while (eventReader.hasNext()) {
XMLEvent event = eventReader.nextEvent();
if (event.isStartElement()) {
StartElement startElement = event.asStartElement();
if (startElement.getName().getLocalPart().equals("record")) {
Record record = new Record();
Iterator<Attribute> attributes = startElement.getAttributes();
while (attributes.hasNext()) {
Attribute attribute = attributes.next();
if (attribute.getName().toString().equals("UID")) {
System.out.println("UID: " + attribute.getValue());
}
}
}
}
}
}
}
Update:
The data in the XML is licensed so I cannot show the full file. This is a very very small segment in which I have scrambled the data.
<?xml version="1.0" encoding="UTF-8"?>
<records>
<REC>
<UID>WOS:000310438600004</UID>
<static_data>
<summary>
<EWUID>
<WUID coll_id="WOS" />
<edition value="WOS.SCI" />
</EWUID>
<pub_info coverdate="NOV 2012" has_abstract="N" issue="5" pubmonth="NOV" pubtype="Journal" pubyear="2012" sortdate="2012-11-01" vol="188">
<page begin="1662" end="1663" page_count="2">1662-1663</page>
</pub_info>
<titles count="6">
<title type="source">JOURNAL OF UROLOGY</title>
<title type="source_abbrev">J UROLOGY</title>
<title type="abbrev_iso">J. Urol.</title>
<title type="abbrev_11">J UROL</title>
<title type="abbrev_29">J UROL</title>
<title type="item">Something something</title>
</titles>
<names count="1">
<name addr_no="1 2 3" reprint="Y" role="author" seq_no="1">
<display_name>John Doe</display_name>
<full_name>John Doe</full_name>
<wos_standard>Doe, John</wos_standard>
<first_name>John</first_name>
<last_name>Doe</last_name>
</name>
</names>
<doctypes count="1">
<doctype>Editorial Material</doctype>
</doctypes>
<publishers>
<publisher>
<address_spec addr_no="1">
<full_address>360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA</full_address>
<city>NEW YORK</city>
</address_spec>
<names count="1">
<name addr_no="1" role="publisher" seq_no="1">
<display_name>ELSEVIER SCIENCE INC</display_name>
<full_name>ELSEVIER SCIENCE INC</full_name>
</name>
</names>
</publisher>
</publishers>
</summary>
</static_data>
</REC>
</records>

A similar solution to lscoughlin's answer is to use DOM4J which has mechanims to deal with this scenario: http://dom4j.sourceforge.net/
In my opionin it is more straight forward and easier to follow. It might not support namespaces, though.

I'm making two assumptions 1) that there is an early level of repetition, and 2) that you can do something meaningful with a partial document.
Let's assume you can move some level of nesting in, and then handle the document multiple times, removing the nodes at the working level each time you "handle" the document. This means that only a single working subtree will be in memory at any given time.
Here's a working code snippet:
package bigparse;
import static javax.xml.stream.XMLStreamConstants.CHARACTERS;
import static javax.xml.stream.XMLStreamConstants.END_DOCUMENT;
import static javax.xml.stream.XMLStreamConstants.END_ELEMENT;
import static javax.xml.stream.XMLStreamConstants.START_DOCUMENT;
import static javax.xml.stream.XMLStreamConstants.START_ELEMENT;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.StringWriter;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
public class BigParse {
public static void main(String... args) {
XMLInputFactory factory = XMLInputFactory.newInstance();
DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
try {
XMLStreamReader streamReader = factory.createXMLStreamReader(new FileReader("src/main/resources/test.xml"));
DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
Document document = documentBuilder.newDocument();
Element rootElement = null;
Element currentElement = null;
int branchLevel = 0;
int maxBranchLevel = 1;
while (streamReader.hasNext()) {
int event = streamReader.next();
switch (event) {
case START_DOCUMENT:
continue;
case START_ELEMENT:
if (branchLevel < maxBranchLevel) {
Element workingElement = readElementOnly(streamReader, document);
if (rootElement == null) {
document.appendChild(workingElement);
rootElement = document.getDocumentElement();
currentElement = rootElement;
} else {
currentElement.appendChild(workingElement);
currentElement = workingElement;
}
branchLevel++;
} else {
workingLoop(streamReader, document, currentElement);
}
continue;
case CHARACTERS:
currentElement.setTextContent(streamReader.getText());
continue;
case END_ELEMENT:
if (currentElement != rootElement) {
currentElement = (Element) currentElement.getParentNode();
branchLevel--;
}
continue;
case END_DOCUMENT:
break;
}
}
} catch (ParserConfigurationException
| FileNotFoundException
| XMLStreamException e) {
throw new RuntimeException(e);
}
}
private static Element readElementOnly(XMLStreamReader streamReader, Document document) {
Element workingElement = document.createElement(streamReader.getLocalName());
for (int attributeIndex = 0; attributeIndex < streamReader.getAttributeCount(); attributeIndex++) {
workingElement.setAttribute(
streamReader.getAttributeLocalName(attributeIndex),
streamReader.getAttributeValue(attributeIndex));
}
return workingElement;
}
private static void workingLoop(final XMLStreamReader streamReader, final Document document, final Element fragmentRoot)
throws XMLStreamException {
Element startElement = readElementOnly(streamReader, document);
fragmentRoot.appendChild(startElement);
Element currentElement = startElement;
while (streamReader.hasNext()) {
int event = streamReader.next();
switch (event) {
case START_DOCUMENT:
continue;
case START_ELEMENT:
Element workingElement = readElementOnly(streamReader, document);
currentElement.appendChild(workingElement);
currentElement = workingElement;
continue;
case CHARACTERS:
currentElement.setTextContent(streamReader.getText());
continue;
case END_ELEMENT:
if (currentElement != startElement) {
currentElement = (Element) currentElement.getParentNode();
continue;
} else {
handleDocument(document, startElement);
fragmentRoot.removeChild(startElement);
startElement = null;
return;
}
}
}
}
// THIS FUNCTION DOES SOMETHING MEANINFUL
private static void handleDocument(Document document, Element startElement) {
System.out.println(stringify(document));
}
private static String stringify(Document document) {
try {
Transformer transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
StreamResult result = new StreamResult(new StringWriter());
DOMSource source = new DOMSource(document);
transformer.transform(source, result);
String xmlString = result.getWriter().toString();
return xmlString;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
EDIT: I made an incredibly silly mistake. It's fixed now. It's working but imperfect -- should be enough to lead you in a useful direction.

Consider using an XSLT 3.0 streaming transformation of the form:
<xsl:template name="main">
<xsl:stream href="bigInput.xml">
<xsl:for-each select="copy-of(/records/REC)">
<!-- process one record -->
</xsl:for-each>
</xsl:stream>
</xsl:template>
You can process this using Saxon-EE 9.6.
The "process one record" logic could use the Saxon SQL extension, or it could invoke an extension function: the context node will be a REC element with its contained tree, fully navigable within the subtree, but with no ability to navigate outside the REC element currently being processed.

Issues with xpath that contained namespaces in Java (Dom parser)

I'm trying to parse an rdfs xml file in order to find all the Classes in an rdfs file.
The xpath: "/rdf:RDF/rdfs:Class"
is working in my XML editor.
When i insert the xpath in my Java program (i have implemented a dom parser), i get 0 Classes.
The following example runs but it outputs 0 classes!
I do:
import java.io.IOException;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPathExpressionException;
import org.xml.sax.SAXException;
public class Main {
public static void main(String args[]) throws XPathExpressionException, ParserConfigurationException, SAXException, IOException{
FindClasses FSB = new FindClasses();
FSB.FindAllClasses("C:\\Workspace\\file.xml"); //rdfs file
}
}
The class FindClasses is as follows:
import java.io.IOException;
import java.util.Collection;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
public class FindClasses {
public void FindAllClasses(String fileName) throws XPathExpressionException, ParserConfigurationException, SAXException, IOException {
DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
domFactory.setNamespaceAware(true);
DocumentBuilder builder = domFactory.newDocumentBuilder();
Document doc = builder.parse(fileName);
XPath xpath = XPathFactory.newInstance().newXPath();
XPathExpression classes_expr = xpath.compile("/rdf:RDF/rdfs:Class");
Object result = classes_expr.evaluate(doc, XPathConstants.NODESET);
NodeList classes = (NodeList) result;
System.out.println("I found : " + classes.getLength() + " classes " );
}
}
The rdfs file is:
<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF xml:lang="en" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
<rdfs:Class rdf:about="Class1">
</rdfs:Class>
<rdfs:Class rdf:about="Class2">
</rdfs:Class>
</rdf:RDF>
I don't really understand why the xpath returns 0 nodes in that example.
It's weird, cause i have implemented other dom parsers as well and they were working fine.
Can somebody help me?
Thanks

I visited the following link and i solved my problem:
Issues with xpath in java
The problem was that the xpath contained two namespaces (rdf,rdfs) like "/rdf:RDF/rdfs:Class".
If the xpath didn't contain any namespace e.g. /RDF/Class , there was not going to be an issue.
So after the line:
xpath = XPathFactory.newInstance().newXPath();
and before the line:
XPathExpression classes_expr = xpath.compile("/rdf:RDF/rdfs:Class");
I added the following:
xpath.setNamespaceContext(new NamespaceContext() {
public String getNamespaceURI(String prefix) {
switch (prefix) {
case "rdf": return "http://www.w3.org/1999/02/22-rdf-syntax-ns#";
case "rdfs" : return "http://www.w3.org/2000/01/rdf-schema#";
}
return prefix;
}
public String getPrefix(String namespace) {
if (namespace.equals("rdf")) return "rdf";
else if (namespace.equals("rdfs")) return "rdfs";
else return null;
}
#Override
public Iterator getPrefixes(String arg0) {
// TODO Auto-generated method stub
return null;
}
});

Find the value of a specific attribute in an XML file in java

I need to just read the value of a single attribute inside an XML file using java. The XML would look something like this:
<behavior name="Fred" version="2.0" ....>
and I just need to read out the version. Can someone point in the direction of a resource that would show me how to do this?

You don't need a fancy library -- plain old JAXP versions of DOM and XPath are pretty easy to read and write for this. Whatever you do, don't use a regular expression.
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
public class GetVersion {
public static void main(String[] args) throws Exception {
XPath xpath = XPathFactory.newInstance().newXPath();
Document doc = DocumentBuilderFactory.newInstance()
.newDocumentBuilder().parse("file:////tmp/whatever.xml");
String version = xpath.evaluate("//behavior/#version", doc);
System.out.println(version);
}
}

JAXB for brevity:
private static String readVersion(File file) {
#XmlRootElement class Behavior {
#XmlAttribute String version;
}
return JAXB.unmarshal(file, Behavior.class).version;
}
StAX for efficiency:
private static String readVersionEfficient(File file)
throws XMLStreamException, IOException {
XMLInputFactory inFactory = XMLInputFactory.newInstance();
XMLStreamReader xmlReader = inFactory
.createXMLStreamReader(new StreamSource(file));
try {
while (xmlReader.hasNext()) {
if (xmlReader.next() == XMLStreamConstants.START_ELEMENT) {
if (xmlReader.getLocalName().equals("behavior")) {
return xmlReader.getAttributeValue(null, "version");
} else {
throw new IOException("Invalid file");
}
}
}
throw new IOException("Invalid file");
} finally {
xmlReader.close();
}
}

Here's one.
import javax.xml.parsers.SAXParser;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.SAXException;
import org.xml.sax.Attributes;
import javax.xml.parsers.SAXParserFactory;
/**
* Here is sample of reading attributes of a given XML element.
*/
public class SampleOfReadingAttributes {
/**
* Application entry point
* #param args command-line arguments
*/
public static void main(String[] args) {
try {
// creates and returns new instance of SAX-implementation:
SAXParserFactory factory = SAXParserFactory.newInstance();
// create SAX-parser...
SAXParser parser = factory.newSAXParser();
// .. define our handler:
SaxHandler handler = new SaxHandler();
// and parse:
parser.parse("sample.xml", handler);
} catch (Exception ex) {
ex.printStackTrace(System.out);
}
}
/**
* Our own implementation of SAX handler reading
* a purchase-order data.
*/
private static final class SaxHandler extends DefaultHandler {
// we enter to element 'qName':
public void startElement(String uri, String localName,
String qName, Attributes attrs) throws SAXException {
if (qName.equals("behavior")) {
// get version
String version = attrs.getValue("version");
System.out.println("Version is " + version );
}
}
}
}

As mentioned you can use the SAXParser.
Digester mentioned using regular expressions, which I won't recommend as it would lead to code that is difficult to maintain: What if you add another version attribute in another tag, or another behaviour tag? You can handle it, but it won't be pretty.
You can also use XPath, which is a language for querying xml. That's what I would recommend.

If all you need is to read the version, then you can use regex. But really, I think you need apache digester

Apache Commons Configuration is nice, too. Commons Digester is based on it.