[Jenkins] Sample function, which gets Node from Jenkins according to StaplerRequest configuration request. Function can be used as workaround for null "node" property at hudson.slaves.NodeProperty

getNodePropertyOwner.java

/**
* Gets Node, which is being configured by StaplerRequest
* @param req StaplerRequest (ex, from NodePropertyDescriptor::newInstance())
* @return Instance of the node, which is being configured (or null)
* 
* @author Oleg Nenashev <nenashev@synopsys.com>
*/
private static Node getNodePropertyOwner(StaplerRequest req)
{                
   List<Ancestor> ancestors = req.getAncestors();          
   if (ancestors.isEmpty())
   {
       assert false : "StaplerRequest is empty";
       return null;
   }
   
   Object node = ancestors.get(ancestors.size()-1).getObject();
   if (SlaveComputer.class.isAssignableFrom(node.getClass()))
   {
       return ((SlaveComputer)node).getNode();
   }
   else
   {
       assert false : "StaplerRequest should have Node ancestor";
       return null;
   }
}

You probably want to use Ancestor rather than manually parsing the request URI!

Yes, Jesse is definitely right.
Previously I've decided to avoid such approach, because I've expected that StaplerRequest::getAncestors() generates list after the first request. BTW, list is available at the start of NodePropertyDescriptor::newInstance()

Fixed code...