Yesterday, again, I needed parser a XML stream using Java.
Then I went to Google try to find a exemple code.
Because I needed the value of two specific fields, TAGs, I decided use XPATH to get directly this values.
How ever, I needed do several tried until get a result.
Keywords
JAVA, XML, NAMESPACE, XML PARSE;
Article
I will show how to read XML without namespace and after we will read a XML streams with namespaces.
This is the first XML that I have used in this example without namespaces
<root>
<head>
<title>My Book</title>
</head>
<bookreview>
<title>This is a book about special girls</title>
<girls>
<girl>
<name>Mata Hari</name>
</girl>
<girl>
<name>Belle de Jour</name>
</girl>
<girl>
<name>Jeanne Bécu, comtesse du Barry</name>
</girl>
<girl>
<name>Phryne</name>
</girl>
</girls>
</bookreview>
</root>
I divided the code into three parts
- One function to read the xml file and to create an instance of an XML Document
- One function to create an instance XPath that provides access to the XPath evaluation environment and expressions.
- One function to find a value in a xml using xpath
1) One function to read the xml file and to create an instance of an XML Document
public static Document getDocument() throws ParserConfigurationException, SAXException, IOException {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setValidating(false);
factory.setIgnoringComments(true);
factory.setIgnoringElementContentWhitespace(true);
DocumentBuilder builder = factory.newDocumentBuilder();
InputStream xmlInput = XMLReader.class.getResourceAsStream("Sample.xml");
Document doc = builder.parse(xmlInput);
xmlInput.close();
return doc;
}
2) One function to create an instance XPath that provides access to the XPath evaluation environment and expressions.
private static XPath xpath;
public static XPath getXPath() {
if (xpath == null) {
XPathFactory factory = XPathFactory.newInstance();
xpath = factory.newXPath();
}
return xpath;
}
3) One function to find a value in a xml using xpath, this example: title
private static void evaluate() throws ParserConfigurationException, SAXException, IOException, XPathExpressionException {
Document doc = getDocument();
Node base = doc.getParentNode();
XPath xpathl = getXPath();
XPathExpression expr = xpathl.compile("//title");
base = (Node)expr.evaluate(doc.getDocumentElement(), XPathConstants.NODE);
if(base!=null)
System.out.println(base.getTextContent());
else
System.out.println("Não Achou");
}
Here we have full class:
package br.com.nivio.util.xml.reader;
import java.io.IOException;
import java.io.InputStream;
import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.xml.namespace.NamespaceContext;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
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.xml.sax.SAXException;
/**
*
* @author NIVIO DOS SANTOS
*/
public class XMLReader{
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
try {
XMLReader.evaluate();
} catch (XPathExpressionException ex) {
Logger.getLogger(XMLReader.class.getName()).log(Level.SEVERE, null, ex);
} catch (ParserConfigurationException ex) {
Logger.getLogger(XMLReader.class.getName()).log(Level.SEVERE, null, ex);
} catch (SAXException ex) {
Logger.getLogger(XMLReader.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(XMLReader.class.getName()).log(Level.SEVERE, null, ex);
}
}
private static void evaluate() throws ParserConfigurationException, SAXException, IOException, XPathExpressionException {
Document doc = getDocument();
Node base = doc.getParentNode();
XPath xpathl = getXPath();
XPathExpression expr = xpathl.compile("//title");
base = (Node)expr.evaluate(doc.getDocumentElement(), XPathConstants.NODE);
if(base!=null)
System.out.println(base.getTextContent());
else
System.out.println("Não Achou");
}
public static Document getDocument() throws ParserConfigurationException, SAXException, IOException {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setValidating(false);
factory.setIgnoringComments(true);
factory.setIgnoringElementContentWhitespace(true);
DocumentBuilder builder = factory.newDocumentBuilder();
InputStream xmlInput = XMLReader.class.getResourceAsStream("Sample.xml");
Document doc = builder.parse(xmlInput);
xmlInput.close();
return doc;
}
private static XPath xpath;
public static XPath getXPath() {
if (xpath == null) {
XPathFactory factory = XPathFactory.newInstance();
xpath = factory.newXPath();
}
return xpath;
}
}
This is the second XML that I have used in this example with namespaces
<?xml version="1.0" encoding="UTF-8"?>
<n1:root xmlns:n1="http://www.nivio.com.br/SpecialGirls" >
<n1:head>
<n1:title>My Book</n1:title>
</n1:head>
<n1:bookreview>
<n1:title>This is a book about special girls</n1:title>
<n1:girls>
<n1:girl>
<n1:name>Mata Hari</n1:name>
</n1:girl>
<n1:girl>
<n1:name>Belle de Jour</n1:name>
</n1:girl>
<n1:girl>
<n1:name>Jeanne Bécu, comtesse du Barry</n1:name>
</n1:girl>
<n1:girl>
<n1:name>Phryne</n1:name>
</n1:girl>
</n1:girls>
</n1:bookreview>
</n1:root>
First of all we need set namespaceAware property in factory, it specifies that the parser produced by this code will provide support for XML namespaces. By default the value of this is set to false
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true); // never forget this!
In this sample, the XML file has prefix "n1" associated to "http://www.nivio.com.br/SpecialGirls" namespace
We have no guarantees that it will always be n1 some times will be n0, nx, or any other value.
We can specify a class to redefine a prefix used in my paths. For example I have used here in xpath the prefix: myPrefix
XPathExpression expr = xpathl.compile("//myPrefix:title");
Here we have this class:
package br.com.nivio.util.xml.reader;
import java.util.Iterator;
import javax.xml.namespace.NamespaceContext;
public class NSContext implements NamespaceContext {
@Override
public String getNamespaceURI(String prefix) {
return "http://www.nivio.com.br/SpecialGirls";
}
@Override
public String getPrefix(String namespaceURI) {
return "myPrefix"; // MY PREFIX
}
@Override
public Iterator getPrefixes(String namespaceURI) {
System.out.println("getPrefixes: namespaceURI: "+namespaceURI);
return null;
}
}
Before compile we will set this NamespaceContext class instance to XPath object
NamespaceContext namepspaceContext= new NSContext();
XPath xpathl = getXPath();
xpathl.setNamespaceContext(namepspaceContext);
Here we have full class:
package br.com.nivio.util.xml.reader;
import java.io.IOException;
import java.io.InputStream;
import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.xml.namespace.NamespaceContext;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
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.xml.sax.SAXException;
/**
*
* @author NIVIO DOS SANTOS
*/
public class XMLReader{
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
try {
XMLReader.evaluate();
} catch (XPathExpressionException ex) {
Logger.getLogger(XMLReader.class.getName()).log(Level.SEVERE, null, ex);
} catch (ParserConfigurationException ex) {
Logger.getLogger(XMLReader.class.getName()).log(Level.SEVERE, null, ex);
} catch (SAXException ex) {
Logger.getLogger(XMLReader.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(XMLReader.class.getName()).log(Level.SEVERE, null, ex);
}
}
private static void evaluate() throws ParserConfigurationException, SAXException, IOException, XPathExpressionException {
Document doc = getDocument();
Node base = doc.getParentNode();
NamespaceContext namepspaceContext= new NSContext();
XPath xpathl = getXPath();
xpathl.setNamespaceContext(namepspaceContext);
XPathExpression expr = xpathl.compile("//myPrefix:title");
base = (Node)expr.evaluate(doc.getDocumentElement(), XPathConstants.NODE);
if(base!=null)
System.out.println(base.getTextContent());
else
System.out.println("Não Achou");
}
public static Document getDocument() throws ParserConfigurationException, SAXException, IOException {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setNamespaceAware(true); // never forget this!
factory.setValidating(false);
factory.setIgnoringComments(true);
factory.setIgnoringElementContentWhitespace(true);
DocumentBuilder builder = factory.newDocumentBuilder();
InputStream xmlInput = XMLReader.class.getResourceAsStream("SampleNS.xml");
Document doc = builder.parse(xmlInput);
xmlInput.close();
return doc;
}
private static XPath xpath;
public static XPath getXPath() {
if (xpath == null) {
XPathFactory factory = XPathFactory.newInstance();
xpath = factory.newXPath();
}
return xpath;
}
}
Obs: Image Jean-Léon Gérôme- Esclave a vendre
Comments
Post a Comment
Thanks for your attention and feedback.
Nivio dos Santos