Use the Web Service Vendor Registration Plugin
if you have a web service that you'd like to integrate into the IDE. Essentially, you paste a WSDL file into a wizard (provided by the plugin), an XML file is generated into your plugin's source structure, which puts a new item in the palette, after you register the XML file, install your plugin, and restart the IDE. Then, when the user drags and drops the item from the palette into the editor, a RESTful resource is created by the IDE. Here's the wizard that generates the XML file:
For full details on everything involved, see the full description on the plugin's page, as well as this recent blog entry.