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How to read namespace as it is in a xml using XMLStreamReader?

I have an xml file from which i read using an XMLStreamReader object.
So i'll keep it simple :
Let's take this xml example :
<mySample xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" attribute1="value1"/>
So what i need is to get the value (as a String) "xmlns:xsi" and get the value (as a String also) "http://www.w3.org/2001/XMLSchema-instance"
I did try to have a test like this :
if (reader.getEventType() != XMLStreamConstants.NAMESPACE){
attributeName = reader.getAttributeLocalName(i);
attributeValue = reader.getAttributeValue(i);
}
else{
attributeName = reader.getNamespacePrefix(i) + reader.getNamespaceURI(i);
attributeValue = reader.getAttributeValue(i);
}
But it did not work.
Obviously i missed something being a newbie to this API, so any help would be very welcome.

The JSR-173 specification (Stax API for Java) states the following regarding the NAMESPACE event :
Namespace
Namespace declarations can also exist outside of a StartElement and may be reported as a
standalone information item. In general Namespaces are reported as part of a StartElement
event. When namespaces are the result of an XQuery or XPath expression they may be
reported as standalone events.
So if you are looking at namespace events, you should most probably be checking StartElement events, and inspect them. Once again, from the spec :
Namespaces can be accessed using the following methods:
int getNamespaceCount();
String getNamespacePrefix(int index);
String getNamespaceURI(int index);
Only the namespaces declared on the current StartElement are available. The list does
not contain previously declared namespaces and does not remove redeclared namespaces.
At any point during the parsing, you can get the current complete namespace context :
The namespace context of the current state is available by calling
XMLStreamReader.getNamespaceContext() or
StartElement.getNamespaceContext(). These methods return an instance of the
javax.xml.namespace.NamespaceContext interface.
That's theory : most namespace declarations come from START_ELEMENT, some may come independently.
In practice, I have never came accross a NAMESPACE event reported by the API when reading from a file. It's almost always reported as part of a START_ELEMENT (and repeated in the corresponding END_ELEMENT), so you must check START_ELEMENT if you are interested in namespace declaration. For example, starting with your document :
String xml = "<?xml version=\"1.0\" encoding=\"utf-8\" ?><mySample xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" attribute1=\"value1\"/>";
XMLStreamReader reader = XMLInputFactory.newFactory().createXMLStreamReader(new StringReader(xml));
while (reader.hasNext()) {
int event = reader.next();
if (XMLStreamConstants.START_ELEMENT == event) {
if (reader.getNamespaceCount() > 0) {
// This happens
System.out.println("ELEMENT START: " + reader.getLocalName() + " , namespace count is: " + reader.getNamespaceCount());
for (int nsIndex = 0; nsIndex < reader.getNamespaceCount(); nsIndex++) {
String nsPrefix = reader.getNamespacePrefix(nsIndex);
String nsId = reader.getNamespaceURI(nsIndex);
System.out.println("\tNamepsace prefix: " + nsPrefix + " associated with URI " + nsId);
}
}
} else if(XMLStreamConstants.NAMESPACE == event) {
// This almost never happens
System.out.println("NAMESPACE EVENT");
}
}
Will produce :
ELEMENT START: mySample , namespace count is: 1
Namepsace prefix: xsi associated with URI http://www.w3.org/2001/XMLSchema-instance
Bottom line : you should check for NAMESPACE and START_ELEMENT events, even if most of times, you will only have START_ELEMENT reporting namespace declartions, it is not one or the other, it's both.

unable to parse a node from xml string with dom4j

I'm parsing a xml string with dom4j and I'm using xpath to select some element from it, the code is :
String test = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><epp xmlns=\"urn:ietf:params:xml:ns:epp-1.0\"><response><result code=\"1000\"><msg lang=\"en-US\">Command completed successfully</msg></result><trID><clTRID>87285586-99412370</clTRID><svTRID>52639BB8-1-ARNES</svTRID></trID></response></epp>";
SAXReader reader = new SAXReader();
reader.setIncludeExternalDTDDeclarations(false);
reader.setIncludeInternalDTDDeclarations(false);
reader.setValidation(false);
Document xmlDoc;
try {
xmlDoc = reader.read(new StringReader(test));
xmlDoc.getRootElement();
Node nodeStatus = xmlDoc.selectSingleNode("//epp/response/result");
System.out.print(nodeStatus.getText());
} catch (DocumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
I always get null for the nodeStatus variable. I actualy nead to read the code from the result noad from the xml
<result code="1000">
This is the XML that I am reading from the String test:
<?xml version="1.0" encoding="UTF-8"?>
<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
<response>
<result code="1000">
<msg lang="en-US">Command completed successfully</msg>
</result>
<trID>
<clTRID>87285586-99412370</clTRID>
<svTRID>52639BB8-1-ARNES</svTRID>
</trID>
</response>
</epp>
Any hints?

Your XML has a namespace. DOM4J returns null because it won't find your nodes.
To make it work, you first have to register the namespaces you are using. You will need a prefix. Any one. And you will have to use that prefix in your XPath.
You could use tns for "target namespace". Then you have to create a xpath object with it like this:
XPath xpath = new DefaultXPath("/tns:epp/tns:response/tns:result");
To register the namespaces you will need to create a Map, add the namespace with the prefix you used in the xpath expression, and pass it to the setNamespaceURIs() method.
namespaces.put("tns", "urn:ietf:params:xml:ns:epp-1.0");
xpath.setNamespaceURIs(namespaces);
Now you can call selectSingleNode, but you will call it on your XPath object passing the document as the argument:
Node nodeStatus = xpath.selectSingleNode(xmlDoc);
From there you can extract the data you need. getText() won't give you the data you want. If you want the contents of the result node as XML, you can use:
nodeStatus.asXML()
Edit: to retrieve just the code, change your XPath to:
/tns:epp/tns:response/tns:result/#code
And retrieve the result with
nodeStatus.getText();
I replaced the double slash // (which means descendant-or-self) with / since the expression contains the full path and / is more efficient. But if you only have one result node in your whole file, you can use:
//result/#code
to extract the data. It will match all descendants. If there is more than one result, it will return a node-set.

Dom4j xmlns attribute

I want to add xmlns attribute to the root node only, however when i add a namespace to the root element, all subsequent child elements also get the same xmlns attribute. How do I add xmlns attribute to a single node but not any of its children ?
CODE:
public String toXml() {
Document document = DocumentHelper.createDocument();
Element documentRoot = document.addElement("ResponseMessage");
documentRoot.addNamespace("",getXmlNamespace())
.addAttribute("xmlns:xsi", getXmlNamespaceSchemaInstance())
.addAttribute("xsi:schemaLocation", getXmlSchemaLocation())
.addAttribute("id", super.getId());
Element header = documentRoot.addElement("Header");
buildHeader(header);
Element body = documentRoot.addElement("Body");
buildProperties(body);
body.addElement("StatusMessage").addText(this.getStatusMessage().getMessage());
return document.asXML();
}

OK, new answer.
If you want your elements to belong to a certain namespace, be sure to create them in that namespace. Use the methods that have Qname as one of its arguments. If you create an element with no namespace, DOM4J will have to add namespace declarations to accommodate to your (unwillingly) specification.
Your example slightly edited. I didn't use QName, but gave each element a namespace uri:
public static String toXml() {
Document document = DocumentHelper.createDocument();
Element documentRoot = document.addElement("ResponseMessage",
getXmlNamespace());
documentRoot.addAttribute(QName.get("schemaLocation", "xsi", "xsi-ns"),
"schema.xsd").addAttribute("id", "4711");
Element header = documentRoot.addElement("Header");
Element body = documentRoot.addElement("Body", getXmlNamespace());
// buildProperties(body);
body.addElement("StatusMessage", getXmlNamespace()).addText("status");
return document.asXML();
}
private static String getXmlNamespace() {
return "xyzzy";
}
public static void main(String[] args) throws Exception {
System.out.println(toXml());
}
produces as output:
<?xml version="1.0" encoding="UTF-8"?>
<ResponseMessage xmlns="xyzzy" xmlns:xsi="xsi-ns" xsi:schemaLocation="schema.xsd" id="4711">
<Header/><Body><StatusMessage>status</StatusMessage></Body>
</ResponseMessage>
UPDATE 2:
Note also, that I changed the way how the schemaLocation attribute is declared. You really never have to manually manage the namespace declarations--this will be taken care of by the library.
However, there is one case where it might be useful to add a namespace delaration: If you have a document with predominantly namespace X elements, and some child elements with namspace Y spread out in the document, declaring a namesapce binding for Y at the root element, may save a lot of repeating name space declarations in the child elements.

Heres how. Its a bit of a hack, but it does what you want:
public static String toXml() {
Document d = DocumentHelper.createDocument();
Namespace rootNs = new Namespace("", DEFAULT_NAMESPACE); // root namespace uri
Namespace xsiNs = new Namespace("xsi", XSI_NAMESPACE); // xsi namespace uri
QName rootQName = QName.get(rootElement, rootNs); // your root element's name
Element root = d.addElement(rootElement);
root.setQName(rootQName);
root.add(xsiNs);
root.addAttribute("xsi:schemaLocation", SCHEMA_LOC)
.addAttribute("id", super.getId());
Element header = documentRoot.addElement("Header");
Element body = documentRoot.addElement("Body", getXmlNamespace());
// buildProperties(body);
body.addElement("StatusMessage", getXmlNamespace()).addText("status");
return document.asXML();
}

Parsing http returned xml with java

So I've tried searching and searching on how to do this but I keep seeing a lot of complicated answers for what I need. I basically am using the Flurry Analytics API to return some xml code from an HTTP request and this is what it returns.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<eventMetrics type="Event" startDate="2011-2-28" eventName="Tip Calculated" endDate="2011-3-1" version="1.0" generatedDate="3/1/11 11:32 AM">
<day uniqueUsers="1" totalSessions="24" totalCount="3" date="2011-02-28"/>
<day uniqueUsers="0" totalSessions="0" totalCount="0" date="2011-03-01"/>
<parameters/>
</eventMetrics>
All I want to get is that totalCount number which is 3 with Java to an int or string. I've looked at the different DOM and SAX methods and they seem to grab information outside of the tags. Is there someway I can just grab totalCount within the tag?
Thanks,
Update
I found this url -http://www.androidpeople.com/android-xml-parsing-tutorial-%E2%80%93-using-domparser/
That helped me considering it was in android. But I thank everyone who responded for helping me out. I checked out every answer and it helped out a little bit for getting to understand what's going on. However, now I can't seem to grab the xml from my url because it requires an HTTP post first to then get the xml. When it goes to grab xml from my url it just says file not found.
Update 2
I got it all sorted out reading it in now and getting the xml from Flurry Analytics (for reference if anyone stumbles upon this question)
HTTP request for XML file

totalCount is what we call an attribute. If you're using the org.w3c.dom API, you call getAttribute("totalCount") on the appropriate element.

If you are using an SAX handler, override the startElement callback method to access attributes:
public void startElement (String uri, String name, String qName, Attributes atts)
{
if("day".equals (qName)) {
String total = attrs.getValue("totalCount");
}
}

A JDOM example. Note the use of SAXBuilder to load the document.
URL httpSource = new URL("some url string");
Document document = SAXBuilder.build(httpSource);
List<?> elements = document.getDescendants(new KeyFilter());
for (Element e : elements) {
//do something more useful with it than this
String total = (Element) e.getAttributeValue("totalCount");
}
class KeyFilter implements Filter {
public boolean matches (Object obj) {
return (Element) obj.getName().equals("key");
}
}

I think that the simplest way is to use XPath, below is an example based on vtd-xml.
import com.ximpleware.*;
public class test {
public static void main(String[] args) throws Exception {
String xpathExpr = "/eventMetrics/day/#totalCount";
VTDGen vg = new VTDGen();
int i = -1;
if (vg.parseHttpUrl("http://localhost/test.xml", true)) {
VTDNav vn = vg.getNav();
AutoPilot ap = new AutoPilot();
ap.selectXPath(xpathExpr);
ap.bind(vn);
System.out.println("total count "+(int)ap.evalXPathtoDouble());
}
}
}

How to insert/replace XML tag in XmlDocument?

I have a XmlDocument in java, created with the Weblogic XmlDocument parser.
I want to replace the content of a tag in this XMLDocument with my own data, or insert the tag if it isn't there.
<customdata>
<tag1 />
<tag2>mfkdslmlfkm</tag2>
<location />
<tag3 />
</customdata>
For example I want to insert a URL in the location tag:
<location>http://something</location>
but otherwise leave the XML as is.
Currently I use a XMLCursor:
XmlObject xmlobj = XmlObject.Factory.parse(a.getCustomData(), options);
XmlCursor xmlcur = xmlobj.newCursor();
while (xmlcur.hasNextToken()) {
boolean found = false;
if (xmlcur.isStart() && "schema-location".equals(xmlcur.getName().toString())) {
xmlcur.setTextValue("http://replaced");
System.out.println("replaced");
found = true;
} else if (xmlcur.isStart() && "customdata".equals(xmlcur.getName().toString())) {
xmlcur.push();
} else if (xmlcur.isEnddoc()) {
if (!found) {
xmlcur.pop();
xmlcur.toEndToken();
xmlcur.insertElementWithText("schema-location", "http://inserted");
System.out.println("inserted");
}
}
xmlcur.toNextToken();
}
I tried to find a "quick" xquery way to do this since the XmlDocument has an execQuery method, but didn't find it very easy.
Do anyone have a better way than this? It seems a bit elaborate.

How about an XPath based approach? I like this approach as the logic is super-easy to understand. The code is pretty much self-documenting.
If your xml document is available to you as an org.w3c.dom.Document object (as most parsers return), then you could do something like the following:
// get the list of customdata nodes
NodeList customDataNodeSet = findNodes(document, "//customdata" );
for (int i=0 ; i < customDataNodeSet.getLength() ; i++) {
Node customDataNode = customDataNodeSet.item( i );
// get the location nodes (if any) within this one customdata node
NodeList locationNodeSet = findNodes(customDataNode, "location" );
if (locationNodeSet.getLength() > 0) {
// replace
locationNodeSet.item( 0 ).setTextContent( "http://stackoverflow.com/" );
}
else {
// insert
Element newLocationNode = document.createElement( "location" );
newLocationNode.setTextContent("http://stackoverflow.com/" );
customDataNode.appendChild( newLocationNode );
}
}
And here's the helper method findNodes that does the XPath search.
private NodeList findNodes( Object obj, String xPathString )
throws XPathExpressionException {
XPath xPath = XPathFactory.newInstance().newXPath();
XPathExpression expression = xPath.compile( xPathString );
return (NodeList) expression.evaluate( obj, XPathConstants.NODESET );
}

How about an object oriented approach? You could deserialise the XML to an object, set the location value on the object, then serialise back to XML.
XStream makes this really easy.
For example, you would define the main object, which in your case is CustomData (I'm using public fields to keep the example simple):
public class CustomData {
public String tag1;
public String tag2;
public String location;
public String tag3;
}
Then you initialize XStream:
XStream xstream = new XStream();
// if you need to output the main tag in lowercase, use the following line
xstream.alias("customdata", CustomData.class);
Now you can construct an object from XML, set the location field on the object and regenerate the XML:
CustomData d = (CustomData)xstream.fromXML(xml);
d.location = "http://stackoverflow.com";
xml = xstream.toXML(d);
How does that sound?

If you don't know the schema the XStream solution probably isn't the way to go. At least XStream is on your radar now, might come in handy in the future!

You should be able to do this with query
try
fn:replace(string,pattern,replace)
I am new to xquery myself and I have found it to be a painful query language to work with, but it does work quiet well once you get over the initial learning curve.
I do still wish there was an easier way which was as efficient?