Java Video Tutorial 45
I received a bunch of emails asking me to make a tutorial on Java XPath. I guess you liked my previous XML XPath tutorial?
XPath can be used to easily grab data from an XML file and into your Java code. I’ll cover how to write to an XML file the easy way in my next tutorial on JDOM2.
All of the code follows the video, and it is heavily commented to help you learn.
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Code from the Video
JAVALESSON45.JAVA
// Provides everything you need to work with the DOM
// Document, Element, Node, NodeList, Text, Exceptions, etc.
import org.w3c.dom.*;
//XPath makes it easy to grab information from an XML document
import javax.xml.xpath.*;
// All the parsers for working with XML
// DocumentBuilder, DocumentBuilderFactory, SAXParser
import javax.xml.parsers.*;
import java.io.IOException;
// SAX Simple API for XML
import org.xml.sax.SAXException;
public class Lesson45 {
public static void main(String[] args){
// Allows your app to get a parser that turns a xml doc into a DOM tree
DocumentBuilderFactory domFactory =
DocumentBuilderFactory.newInstance();
// Provides support for XML namespaces if needed
domFactory.setNamespaceAware(true);
// Turns xml into a DOM tree
DocumentBuilder builder;
Document doc = null;
try {
// parses the file supplied
builder = domFactory.newDocumentBuilder();
doc = builder.parse("./src/tvshows5.xml");
}
catch (SAXException e) {
e.printStackTrace();
}
catch (IOException e) {
e.printStackTrace();
}
catch (ParserConfigurationException e) {
e.printStackTrace();
}
// Allows you to grab data from the document using the codes below
XPath xpath = XPathFactory.newInstance().newXPath();
getNodeNameAndValue(doc, xpath);
}
private static void getNodeNameAndValue(Document doc, XPath xpath){
// XPath Query
XPathExpression expr;
Object result = null;
try {
// Returns characters with the profession Student
expr = xpath.compile("//show/actors/actor/character[@profession='Student']//text()");
// Returns the result of the query
result = expr.evaluate(doc, XPathConstants.NODESET);
}
catch (XPathExpressionException e) {
e.printStackTrace();
}
// Outputs the results of the query
NodeList nodes = (NodeList) result;
// Cycles through the results
for (int i = 0; i < nodes.getLength(); i++) {
// Print the matching node name and value
System.out.println(nodes.item(i).getParentNode().getNodeName() + " " + nodes.item(i).getNodeValue());
}
// Display every name
// : //show/name//text()
// Display everything
// : //show/*//text()
// Show names based on an attribute
// : //show/name[@id_code='show_001']//text()
// Show actors and character names
// : //show/actors/actor/*//text()
// Show character names if they are Students
// : //show/actors/actor/character[@profession='Student']//text()
}
}
XML FILE USED
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE tvshow SYSTEM "tvshows5.dtd" >
<?xml-stylesheet type="text/xsl" href="tvshows5.xsl" ?>
<tvshow>
<show>
<name id_code="show_001">Life On Mars</name>
<release>2008</release>
<network country="US">ABC</network>
<description>The series tells the story of New York City police detective Sam Tyler.</description>
<actors>
<actor>
<real_name>Jason O'Mara</real_name>
<character profession="Detective">Sam Tyler</character>
</actor>
<actor>
<real_name>Michael Imperioli</real_name>
<character profession="Detective">Ray Carling</character>
</actor>
</actors>
<poster href="http://ia.media-imdb.com/images/M/MV5BMTM4MDg2NTk1OF5BMl5BanBnXkFtZTcwNzI4OTY5MQ@@._V1._SY317_CR12,0,214,317_.jpg" width="214" height="317" />
<viewers units="million">7.82</viewers>
<end_date>2009</end_date>
</show>
<show>
<name id_code="show_002">Life On Mars</name>
<release>2006</release>
<network country="UK">BBC</network>
<description>The series combines elements of science fiction and police procedural.</description>
<actors>
<actor>
<real_name>John Simm</real_name>
<character profession="Detective">Sam Tyler</character>
</actor>
<actor>
<real_name>Philip Glenister</real_name>
<character profession="Detective">Gene Hunt</character>
</actor>
</actors>
<poster href="http://ia.media-imdb.com/images/M/MV5BMTQxNzc5MjQwNF5BMl5BanBnXkFtZTcwMjU3Njc4Mg@@._V1._SY317_CR8,0,214,317_.jpg" width="214" height="317" />
<viewers units="million">6.8</viewers>
<end_date>2007</end_date>
</show>
<show>
<name id_code="show_003">Freaks and Geeks</name>
<release>1999</release>
<network country="US">ABC</network>
<description>The show centers on a teenage girl, Lindsay Weir, and her brother, Sam, who both attend William McKinley High School during the 1980–1981 school year in the town of Chippewa, Michigan, a fictional suburb of Detroit.</description>
<actors>
<actor>
<real_name>Linda Cardellini</real_name>
<character profession="Student">Lindsay Weir</character>
</actor>
<actor>
<real_name>John Francis Daley</real_name>
<character profession="Student">Sam Weir</character>
</actor>
</actors>
<poster href="http://ia.media-imdb.com/images/M/MV5BMTQ5OTEzODYyMl5BMl5BanBnXkFtZTcwMjcxNTcwMg@@._V1._SY317_CR24,0,214,317_.jpg" width="214" height="317" />
<viewers units="million">6.77</viewers>
<end_date>2000</end_date>
</show>
<show>
<name id_code="show_004">Pushing Daisies</name>
<release>2007</release>
<network country="US">ABC</network>
<description>The series stars Lee Pace as Ned, a pie-maker with the ability to bring dead things back to life with his touch, an ability that comes with stipulations.</description>
<actors>
<actor>
<real_name>Lee Pace</real_name>
<character profession="Baker">Ned</character>
</actor>
<actor>
<real_name>Anna Friel</real_name>
<character profession="Baker">Charlotte Chuck Charles</character>
</actor>
</actors>
<poster href="http://ia.media-imdb.com/images/M/MV5BMTY3ODYxNjU1Nl5BMl5BanBnXkFtZTcwMTI0MTU1MQ@@._V1._SY317_CR0,0,214,317_.jpg" width="214" height="317" />
<viewers units="million">7.78</viewers>
<end_date>2009</end_date>
</show>
</tvshow>
i would like to have compare two xmls which is having the namespace.
Please explain how we can do it.
Thanks,
Chandra
That shouldn’t really happen ever if proper namespaces are defined
I am not able to rad this xml
WFS
1212503
OMNISALE
1
ZONA1
30/04/2008
can you please help me on this
That is because your xml does not have any elements.
Nice video. I got a problem to run the same code and same XML file on my mac. I have not made any changes. I installed Java JDK 1.7 as shown here (http://www.newthinktank.com/2011/12/install-java-1-7-eclipse/). I’m very sure from the correct file path. Although that, I got this error:
java.io.FileNotFoundException: /Users/follower/myXPath/src/tvshows5.dtd (No such file or directory)
Keep all of your files in the same folder and you won’t have any problems. It is recommended to save in src – default package for your project in Eclipse
Just delete
line from xml file..
and run it
thx dude, i really need this!!
You’re very welcome 🙂