ADF Faces: how to extend one of the faces components

Question

Hi all,
I am thinking of extending the built-in ADF Faces CommandMenuItem component (to work around a bug that was filed). The only thing that I think I need to do is to add an additional property - I don't believe that I will need to add any additional behavior to the tag.
Can anyone comment on (high level) the steps that I would need to go through? I'd like to
a). Add the property
b). Make sure the property shows up in the JDev property inspector
c). Inherit everything else from CoreCommandMenuItem.
I've looked at the source code (from the Apache guys), and this doesn't look too hard. I don't want to re-compile the whole Apache drop, just create a new component as described above, but I've no idea really where to start.
Any insights appreciated,
John

Answer 1

Hello John,
I don't know how possible it will be. It depend on what kind of property you want to add. Here are the general indications to acheive this.
1) Make a custom component class extending CommandMenuItem class and add an additional property.
2) Extends the commandMenuItem tag clas with your own
3) override the method public void setProperties(javax.faces.component.UIComponent component)
you just have to call the parent first which is the specification behavior anyway, so:
public void setProperties(UIComponent component) {
super.setProperties(component);
// Cast the component to your component class and set your additional property on it
4) The hard part... This is where I'm unsure of the procedure, but I would say that you'll have to extends ADF Faces's renderer for commandMenuItem and find a way to push the property in it if it has to be sent to the client. This seem really annoying to do. One way to do it would be to wrap the ResponseWriter so you can intercept what the parent renderer encodes and insert your property in the right spot. That strategy requires an additional (probably intern) class extending ResponseWriter. Then you would have to do something like this:
FacesContext context = FacesContext.getCurrentInstance();
ResponseWriter initial = context.getResponseWriter();
context.setResponseWriter(new MyWrapperWriter(initial));
super.encodeBegin(context, component);
context.setResponseWriter(initial);
The Wrapper would have to override all methods and delegate the call to the wrapped instance. When calling startElement(String) you would add a call to writeAttribute for your own property.
5) For showing the property in the property editor panel you must fill a faces-config.xml file with the <component> tag. Since that one does not allow inheritance (which is really annoying imho) you'll have to copy most of the properties from adf faces' faces-config.xml file.
6) Fill the tld for your new tag
7) JAR the whole thing
8) Edit your tag library from Tool in the menu I think (not on a computer with JDev installed atm so cannot be sure). Add your library that you just created. If faces.config.xml and the .tld are well made JDev will figure prety much everything on its own. You will now have a new choice in the dropdown menu of the component palette for your custom library.
I hope I was decently clear.
Regards,
Simon Lessard