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How to write XPath to get node attribute value from a "Name Space XML" in Java

INPUT_XML:
<?xml version="1.0" encoding="UTF-8">
<root xmlns:ns1="http://path1/schema1" xmlns:ns2="http://path2/schema2">
<ns1:abc>1234</ns1:abc>
<ns2:def>5678</ns2:def>
</root>
In Java, I am trying to write XPath expression which will get the value corresponding to this attribute "xmlns:ns1" from the above INPUT_XML string content.
I've tried the following:
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
DocumentBuilder builder = factory.newDocumentBuilder();
Document document = builder.parse(INPUT_XML);
String xpathExpression = "/root/xmlns:ns1";
// Create XPathFactory object
XPathFactory xpathFactory = XPathFactory.newInstance();
// Create XPath object
XPath xpath = xpathFactory.newXPath();
// Create XPathExpression object
XPathExpression expr = xpath.compile(xpathExpression);
// Evaluate expression result on XML document
NodeList nodes = (NodeList) expr.evaluate(document, XPathConstants.NODESET);
for (int i = 0; i < nodes.getLength(); i++) {
System.out.println(nodes.item(i).getNodeValue());
}
But the above code is not giving the expected value of the specified attribute i.e. xmlns:ns1. I heavily suspect the xPathExpression is wrong. Please suggest with the right XPath expression or the right approach to tackle this issue.

If you're using an XPath 1.0 processor, or a XPath 2.0 processor with XPath 1.0 compatibility mode turned on, you can use the namespace axis to select the namespace value.
You will need to make the following change in your code:
String xpathExpression = "/root/namespace::ns1"

The xmlns:ns1="http://path1/schema1" and xmlns:ns2="http://path2/schema2" are not attributes, but namespace declarations. You cannot retrieve them with an XPath declaration so easily (there is XPath function namespace-uri() for this purpose, but root element does not have any namespace, it only defines them for future use).
When using DOM API you could use method lookupNamespaceURI():
System.out.println("ns1 = " + doc.getDocumentElement().lookupNamespaceURI("ns1"));
System.out.println("ns2 = " + doc.getDocumentElement().lookupNamespaceURI("ns2"));
When using XPath you could try following expressions:
namespace-uri(/*[local-name()='root']/*[local-name()='abc'])
namespace-uri(/*[local-name()='root']/*[local-name()='def'])

How I can extract parameters from xml?

How I can extract value Total topics?
<?xml version="1.0"?>
<config>
<command param = "Total topics" > Check title
</command>
</config>
I know that for extracting value of Check title I need such code:
XPathExpression expr = xpath.compile("//command/text()");
Object result = expr.evaluate(doc, XPathConstants.NODESET);
Help me with param, please.

XPathExpression expr = xpath.compile("//command[#param]/text()");
Object result = expr.evaluate(doc, XPathConstants.NODESET);
I've not compiled it but to select an attribute you'll need to used #attributeName after the node is selected.

How about using # for attribute? Try with
XPathExpression expr = xpath.compile("//command/#param");

How to access to value read XML using XPath in Java

I want to read XML data using XPath in Java.
I have the next XML file named MyXML.xml:
<?xml version="1.0" encoding="iso-8859-1" ?>
<REPOSITORY xmlns:LIBRARY="http://www.openarchives.org/LIBRARY/2.0/"
xmlns:xsi="http://www.w3.prg/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.openarchives.org/LIBRARY/2.0/ http://www.openarchives.org/LIBRARY/2.0/LIBRARY-PHM.xsd">
<repository>Test</repository>
<records>
<record>
<ejemplar>
<library_book:book
xmlns:library_book="http://www.w3c.es/LIBRARY/book/"
xmlns:book="http://www.w3c.es/LIBRARY/book/"
xmlns:bookAssets="http://www.w3c.es/LIBRARY/book/"
xmlns:bookAsset="http://www.w3c.es/LIBRARY/book/"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3c.es/LIBRARY/book/ http://www.w3c.es/LIBRARY/replacement/book.xsd">
<book:bookAssets count="1">
<book:bookAsset nasset="1">
<book:bookAsset.id>value1</book:bookAsset.id>
<book:bookAsset.event>
<book:bookAsset.event.id>value2</book:bookAsset.event.id>
</book:bookAsset.event>
</book:bookAsset>
</book:bookAssets>
</library_book:book>
</ejemplar>
</record>
</records>
</REPOSITORY>
I want access to value1 and value2 values. For this, I try this:
// Standard of reading a XML file
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true);
DocumentBuilder builder;
Document doc = null;
XPathExpression expr = null;
builder = factory.newDocumentBuilder();
doc = builder.parse("MyXML.xml");
// Create a XPathFactory
XPathFactory xFactory = XPathFactory.newInstance();
// Create a XPath object
XPath xpath = xFactory.newXPath();
expr = xpath.compile("//REPOSITORY/records/record/ejemplar/library_book:book//book:bookAsset.event.id/text()");
Object result = expr.evaluate(doc, XPathConstants.STRING);
System.out.println("RESULT=" + (String)result);
But I don't get any results. Only prints RESULT=.
¿How to access to value1 and value2 values?. ¿What is the XPath filter to apply?.
Thanks in advanced.
I'm using JDK6.

You are having problems with namespaces, what you can do is
take them into account
ignore them using the XPath local-name() function
Solution 1 implies implementing a NamespaceContext that maps namespaces names and URIs and set it on the XPath object before querying.
Solution 2 is easy, you just need to change your XPath (but depending on your XML you may fine-tune your XPath to be sure to select the correct element):
XPath xpath = xFactory.newXPath();
expr = xpath.compile("//*[local-name()='bookAsset.event.id']/text()");
Object result = expr.evaluate(doc, XPathConstants.STRING);
System.out.println("RESULT=" + result);
Runnable example on ideone.
You can take a look at the following blog article to better understand the uses of namespaces and XPath in Java (even if old)

Try
Object result = expr.evaluate(doc, XPathConstants.NODESET);
// Cast the result to a DOM NodeList
NodeList nodes = (NodeList) result;
for (int i=0; i<nodes.getLength();i++){
System.out.println(nodes.item(i).getNodeValue());
}

One approach is to implement a name space context like:
public static class UniversalNamespaceResolver implements NamespaceContext {
private Document sourceDocument;
public UniversalNamespaceResolver(Document document) {
sourceDocument = document;
}
public String getNamespaceURI(String prefix) {
if (prefix.equals(XMLConstants.DEFAULT_NS_PREFIX)) {
return sourceDocument.lookupNamespaceURI(null);
} else {
return sourceDocument.lookupNamespaceURI(prefix);
}
}
public String getPrefix(String namespaceURI) {
return sourceDocument.lookupPrefix(namespaceURI);
}
public Iterator getPrefixes(String namespaceURI) {
return null;
}
}
And then use it like
xpath.setNamespaceContext(new UniversalNamespaceResolver(doc));
You also need to move up all the namespace declarations to the root node (REPOSITORY). Otherwise it might be a problem if you have namespace declarations on two different levels.

Getting the value of an attribute in Java from a XML using XPath

I'm currently using XPath to get some information from a podcast feed using Java and XPath. I'm trying to read the attribute of a node:
<?xml version="1.0" encoding="UTF-8"?>
<rss xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:sy="http://purl.org/rss/1.0/modules/syndication/" xmlns:admin="http://webns.net/mvcb/" xmlns:atom="http://www.w3.org/2005/Atom/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:itunes="http://www.itunes.com/dtds/podcast-1.0.dtd" version="2.0">
<channel>
[....]
<itunes:image href="http://icebox.5by5.tv/images/broadcasts/14/cover.jpg" />
[...]
I want to get the value of the href attribute in <itunes:image>. Currently, I'm using the following code:
private static String IMAGE_XPATH = "//channel/itunes:image/#href";
String imageUrl = xpath.compile(IMAGE_XPATH).evaluate(doc, XPathConstants.STRING).toString();
The result of imageUrl is null. What happens in the code? Do I have an error in the XPath code, or in the Java code?
Thanks! :)

Disable namespace awarness:
DocumentBuilderFactory xmlFact = DocumentBuilderFactory.newInstance();
xmlFact.setNamespaceAware(false);
Your xpath expression should look like this now:
"//channel/image/#href"
If you need to use it as namespace aware, just implement your own NameSpaceContext, should look like this:
NamespaceContext ctx = new ItunesNamespaceContext();
XPathFactory xpathFact = XPathFactory.newInstance();
XPath xpath = xpathFact.newXPath();
xpath.setNamespaceContext(ctx);
String IMAGE_XPATH = "//channel/itunes:image/#href";
String imageUrl = path.compile(IMAGE_XPATH).evaluate(doc,XPathConstants.STRING).toString();
EDIT: Here is a test code that proves my point:
String a ="<?xml version=\"1.0\" encoding=\"UTF-8\"?><rss xmlns:dc=\"http://purl.org/dc/elements/1.1/\" xmlns:sy=\"http://purl.org/rss/1.0/modules/syndication/\" xmlns:admin=\"http://webns.net/mvcb/\" xmlns:atom=\"http://www.w3.org/2005/Atom/\" xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\" xmlns:content=\"http://purl.org/rss/1.0/modules/content/\" xmlns:itunes=\"http://www.itunes.com/dtds/podcast-1.0.dtd\" version=\"2.0\"><channel><itunes:image href=\"http://icebox.5by5.tv/images/broadcasts/14/cover.jpg\" /></channel></rss>";
DocumentBuilderFactory xmlFact = DocumentBuilderFactory.newInstance();
xmlFact.setNamespaceAware(false);
DocumentBuilder builder = xmlFact.newDocumentBuilder();
XPathFactory xpathFactory = XPathFactory.newInstance();
String expr = "//channel/image/#href";
XPath xpath = xpathFactory.newXPath();
Document doc = builder.parse(new InputSource(new StringReader(a)));
String imageUrl = (String) xpath.compile(expr).evaluate(doc ,XPathConstants.STRING);
System.out.println(imageUrl);
The output is:
http://icebox.5by5.tv/images/broadcasts/14/cover.jpg

The XPath should include the root element, so rss/channel/itunes:image/#href.
Alternatively, you could start the xpath with a // so that all levels are searched for the xpath (//channel/itunes:image/#href) but if the root will always be the same it is more efficient to use the first option.

Document - How to get a tag's value by its name?

I'm using Java's DOM parser to parse an XML file.
let's say I have the following XML
<?xml version="1.0"?>
<config>
<dotcms>
<endPoint>ip</endPoint>
</dotcms>
</config>
</xml>
I like to get the value of 'endPoint'. I can do it with the following code snippet. (assuming that I already parsed it with DocumentBuilder)
NodeList nodeList = this.doc.getElementByTagName("dotcms");
Node nValue = (Node) nodeList.item(0);
return nValue.getNodeValue();
Is it possible to get a value of a field by a field's name? Like....
Node nValue = nodeList.getByName("endPoint") something like this...?

You should use XPath for these sorts of tasks:
//endPoint/text()
or:
/config/dotcms/endPoint/text()
Of course Java has a built-in support for XPath:
XPath xpath = XPathFactory.newInstance().newXPath();
XPathExpression expr = xpath.compile("//endPoint/text()");
Object value = expr.evaluate(doc, XPathConstants.STRING);

You could also use jOOX, a jquery-like DOM wrapper, to write even less code:
// Using css-style selectors
String text1 = $(document).find("endPoint").text();
// Using XPath
String text2 = $(document).xpath("//endPoint").text();