XPath in Java

XPath is support in Java by default. In other to use is, you need to parse XML document using DOM (or maybe SAX -- I don't know if that works). Either way, when you do that, just call XPathFactory.newInstance().newXPath() and call evaluate method, like in following example:

public static Object xPathQuery(String expression, File file) {
         Document document;
         DocumentBuilderFactory dBF = DocumentBuilderFactory.newInstance();
         Object result = null;
         try {
             DocumentBuilder builder = dBF.newDocumentBuilder();
             document = builder.parse(file);
             
             XPath xpath = XPathFactory.newInstance().newXPath();
             XPathExpression expr = xpath.compile(expression);

             result = expr.evaluate(document, XPathConstants.NODESET);             
         } catch (Exception e) {
             e.printStackTrace();
         }
         return result;
     }

You can see that this method returns Object. This object can be cast to boolean, String or (more useful) NodeList. Be careful, this type depends of type of your XPath query. So for example to extract NodeList from XPath query that returns multiple nodes will look like this:

NodeList nodes = (NodeList) xPathQuery("//employees", new File("C:/some_xml"));

int j = nodes.getLength();

for (int i = 0; i < j; i++) {
    System.out.println(nodes.item(i).getTextContent());
}

And that's it!

Saxon XSLT Java example

I was looking for simple Saxon XSLT transformation example using Java and I could not find one that is simple and descriptive enough, so I made one and I hope it will helpful for someone. So here it is :

import java.io.File;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

public class Main {

    /**
     * Simple transformation method.
     * @param sourcePath - Absolute path to source xml file.
     * @param xsltPath - Absolute path to xslt file.
     * @param resultDir - Directory where you want to put resulting files.
     */
    public static void simpleTransform(String sourcePath, String xsltPath,
                                       String resultDir) {
        TransformerFactory tFactory = TransformerFactory.newInstance();
        try {
            Transformer transformer =
                tFactory.newTransformer(new StreamSource(new File(xsltPath)));

            transformer.transform(new StreamSource(new File(sourcePath)),
                                  new StreamResult(new File(resultDir)));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        //Set saxon as transformer.
        System.setProperty("javax.xml.transform.TransformerFactory",
                           "net.sf.saxon.TransformerFactoryImpl");

        simpleTransform("d:/project/hob/AppModule.xml",
                        "d:/project/hob/create-fragment.xslt", "C:/");

    }
}

You just need to put Saxon library into project CLASSPATH. This example create resulting file(s) on the root of C: drive.

Have fun!

Slow JDeveloper

Speed up JDeveloper


There are times when JDeveloper slow down so much that it becomes unusable. For example you need to wait 5-30 seconds for simple text change or you wait for structure window to refresh. This can happen when you have complex .jspx pages and when all your components are binds to backing bean.

There are some serious issues with JDeveloper memory management. This can be due to Java Swing API, but this is just wild guest and I really don't know nothing about this.

Eater way, to solve this problem you have two choices:
Use external editor (This is not so good solution).
Other (much better) is to disable automatic component binding by removing binding line from your jspx page. This will rise performance to acceptable level (noting spectacular).

General tip is not to have complex Java backing bean pages and complex .jspx pages (use fragments to simplify layout).