For online, I used this to test WADL with good results. http://www.utilities-online.info/xsdvalidation/
You can get the XSD for WADL from the W3C website here: http://www.w3.org/Submission/wadl/wadl.xsd
The online tool is very easy to use. Your WADL goes to the left pane, and XSD to another. It takes some time to check, so you may have to talk your browser a bit ...
I also used oXygen against the same XSD and would recommend it in an online tool. It checks how you print, if you create a large number of WADL, then it really costs a license. http://www.oxygenxml.com/
Another visual tool is Altova's XML Spy. I have not used this for a while, but they have a large selection of products, and it is worth considering whether you can use other tools from your package, for example. diffdog is considered very good. http://www.altova.com/xmlspy.html
Finally, the NetBeans IDE has support, but it seems too complicated to use the IDE to create WADLs. It's not easy: -)
source share