UiXML event handlers - how to define once across pages

Question

I have a number of event handlers which will be used by several of my pages. Is there a way of including the definitions in each of those pages having only defined them once?
Cheers
Ian

Answer 1

The simplest approach is to override AbstractPageBroker.getEventHandler() - but
that requires that the page broker have global knowledge of all your pages.
So, what follows is a way to add a single element to any of your pages that will
add event handlers (in this case, a single handler).
It's a little less trivial than I'd assumed, but I've included here actual functional
source code to implement the whole thing. This is a very, very silly example;
it lets you add a single element to a page:
<page xmlns="http://xmlns.oracle.com/uix/controller">
  <scream xmlns="http://www.example.org/scream"/>
...With this element, the "scream" event will be handled by, well, screaming.
Silly, yes; but it demonstrates the technique. Exactly the same technique
would also let you execute code immediately before and/or immediately after
a page renders (e.g., automatically register data providers). Here's the code;
it's four classes, but they're all small.
ScreamUIExtension[b]
package scream;
import oracle.cabo.ui.UIExtension;
import oracle.cabo.ui.laf.LookAndFeel;
import oracle.cabo.share.xml.ParserManager;
public class ScreamUIExtension implements UIExtension
  public void registerSelf(ParserManager manager)
    manager.registerExtension("http://www.example.org/scream",
                              new ScreamParserExtension());
  public void registerSelf(LookAndFeel laf)
}[b]ScreamParserExtension
package scream;
import java.util.Dictionary;
import org.xml.sax.Attributes;
import oracle.cabo.share.xml.BaseParserExtension;
import oracle.cabo.share.xml.LeafNodeParser;
import oracle.cabo.share.xml.NodeParser;
import oracle.cabo.share.xml.ParseContext;
import oracle.cabo.servlet.ui.UINodePageDescription;
public class ScreamParserExtension extends BaseParserExtension
  public NodeParser startExtensionElement(
    ParseContext context,
    String       namespaceURI,
    String       localName,
    Attributes   attrs)
    if ("scream".equals(localName))
      return new LeafNodeParser()
        protected Object getNodeValue(
          ParseContext context,
          String       namespaceURI,
          String       localName,
          Attributes   attrs)
          return "This doesn't matter in this example...";
    return null;
  public Object elementEnded(
    ParseContext context,
    String       namespaceURI,
    String       localName,
    Object       parsed,
    Dictionary   attributes)
    Object value = attributes.get("scream");
    if (value == null)
      return parsed;
    if (!(parsed instanceof UINodePageDescription))
      logWarning(context,
                 "The \"scream\" elements may only be used inside of <page>");
      return parsed;
    return new ScreamPageDescription((UINodePageDescription) parsed);
ScreamPageDescription
package scream;
import oracle.cabo.servlet.ui.UINodePageDescription;
import oracle.cabo.servlet.ui.UINodePageDescriptionProxy;
import oracle.cabo.servlet.BajaContext;
import oracle.cabo.servlet.event.EventHandler;
import oracle.cabo.servlet.event.TableEventHandler;
public class ScreamPageDescription extends UINodePageDescriptionProxy
  public ScreamPageDescription(UINodePageDescription uinpd)
    _uinpd = uinpd;
  public EventHandler getEventHandler(BajaContext context)
    TableEventHandler teh = new TableEventHandler();
    teh.registerEventHandler("scream", new ScreamEventHandler());
    teh.setDefaultEventHandler(getPageDescription().getEventHandler(context));
    return teh;
  protected UINodePageDescription getPageDescription()
    return _uinpd;
  private final UINodePageDescription _uinpd;
ScreamEventHandler
package scream;
import oracle.cabo.servlet.BajaContext;
import oracle.cabo.servlet.Page;
import oracle.cabo.servlet.event.EventHandler;
import oracle.cabo.servlet.event.EventResult;
import oracle.cabo.servlet.event.PageEvent;
public class ScreamEventHandler implements EventHandler
  public EventResult handleEvent(
    BajaContext   context,
    Page          page,
    PageEvent     event)
    System.out.println("SCREAM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
    return null;
}Now, to register these, you'll want a WEB-INF/uix-config.xml like so:
<configurations xmlns="http://xmlns.oracle.com/uix/config">
  <application-configuration>
    <ui-extensions>
      <extension-class>scream.ScreamUIExtension</extension-class>
    </ui-extensions>
  </application-configuration>
</configurations>If you did want to add pre- or post-rendering code, just override
different methods inside your PageDescription class.
Final note: all of this should work unmodified in 9.0.2 except for
the uix-config.xml; you'd have to use the older, deprecated WEB-INF/web.xml
UIX configuration parameters in 9.0.2.