A good thing to do is to look at existing components:
If you are working with the Orbeon Forms sources, most components are located under:
If you are working with a binary distribution:
unzip orbeon-resources-private.jar
the components are under the xbl directory
The "meat" of most components is in files ending with the .xbl extension.
create a new xbl directory under your RESOURCES directory
create a directory with your company or project name (e.g. acme; Orbeon uses orbeon)
create directory with your new component name (e.g. cool-stuff)
create a new XBL file with the same name in that directory, e.g. cool-stuff.xbl
so you should have: xbl/acme/cool-stuff/cool-stuff.xbl
Then:
copy into your XBL file the content of a simple existing component, like tutorial-input.xbl
modify the binding rule (fr|tutorial-simple) into something that matches your component name (fr|cool-stuff)
within an XForms page
declare xmlns:fr="http://orbeon.org/oxf/xml/form-runner"
use the control with something like: <fr:cool-stuff ref="my-node">
when running your XForms page, you should see an upload field appear!
NOTE: In your own components, you should not use the fr: namespace, but instead you should use your own namespace to avoid naming conflicts.
