title: JEXL: How to customize property accessors
body: <p>I've got data objects, which you could think of as a "simplified map". There are methods <code>get(String)</code>, and <code>put(String,Object)</code>, but that's basically it.</p>
  
  <p>Now, I'd like to use JEXL to evaluate complex expressions on my data objects. I can do so by creating a custom JexlContext, and that works for expressions like <em>"foo"</em>, or <code>foo != null</code>. However, as soon as I attempt to use an expression like <em>"foo.bar"</em>, Jexl fails with an error message "unsolvable property".
  Obviously, Jexl uses my custom JexlContext to evaluate <em>"foo"</em>, but can't evaluate <em>"bar"</em> on the foo object.
  My impression is, that I've got to use a custom PropertyResolver. I can implement that, but I can't figure out. how to bring that into the game, as the JexlUberspect doesn't contain a method like <code>setResolvers</code>, or <code>addResolver</code>.</p>