Cursor-to-Event Example

Located in the tut-install/javaeetutorial5/examples/stax/cursor2event/ directory, CursorApproachEventObject.java demonstrates how to get information returned by an XMLEvent object even when using the cursor API.

The idea here is that the cursor API’s XMLStreamReader returns integer constants corresponding to particular events, while the event iterator API’s XMLEventReader returns immutable and persistent event objects. XMLStreamReader is more efficient, but XMLEventReader is easier to use, because all the information related to a particular event is encapsulated in a returned XMLEvent object. However, the disadvantage of event approach is the extra overhead of creating objects for every event, which consumes both time and memory.

With this mind, XMLEventAllocator can be used to get event information as an XMLEvent object, even when using the cursor API.

Instantiating an XMLEventAllocator

The first step is to create a new XMLInputFactory and instantiate an XMLEventAllocator:

XMLInputFactory xmlif = XMLInputFactory.newInstance();
System.out.println("FACTORY: " + xmlif);
xmlif.setEventAllocator(new XMLEventAllocatorImpl());
allocator = xmlif.getEventAllocator();
XMLStreamReader xmlr = xmlif.createXMLStreamReader(filename,
    new FileInputStream(filename));

Creating an Event Iterator

The next step is to create an event iterator:

int eventType = xmlr.getEventType();
while(xmlr.hasNext()){
    eventType = xmlr.next();
    //Get all "Book" elements as XMLEvent object
    if(eventType == XMLStreamConstants.START_ELEMENT &&
        xmlr.getLocalName().equals("Book")){
        //get immutable XMLEvent
        StartElement event = getXMLEvent(xmlr).asStartElement();
        System.out.println("EVENT: " + event.toString());
    }
}

Creating the Allocator Method

The final step is to create the XMLEventAllocator method:

private static XMLEvent getXMLEvent(XMLStreamReader reader)
         throws XMLStreamException {
    return allocator.allocate(reader);
}

Building and Running the Cursor-to-Event Example Using NetBeans IDE

Follow these instructions to build and run the Cursor-to-Event example on your Application Server instance using the NetBeans IDE.

1. In NetBeans IDE, select File->Open Project.

2. In the Open Project dialog, navigate to the tut-install/javaeetutorial5/examples/stax/ directory.

3. Select the cursor2event folder.

4. Select the Open as Main Project check box.

5. Click Open Project.

6. In the Projects tab, right-click the cursor2event project and select Properties. The Project Properties dialog is displayed.

7. Enter the following in the Arguments field:

   BookCatalog.xml

8. Click OK.

9. Right-click the cursor2event project and select Run.

   Note how the Book events are returned as strings.

Building and Running the Cursor-to-Event Example Using Ant

To compile and run the Cursor-to-Event example using Ant, in a terminal window, go to the tut-install/javaeetutorial5/examples/stax/cursor2event/ directory and type the following:

ant run-cursor2event