context = JXPathContext.newContext(new TestMixedModelBean());
context.setFactory(new VariableFactory());
Variables vars = context.getVariables();
vars.declareVariable("a", new Double(1));
vars.declareVariable("b", new Double(1));
vars.declareVariable("c", null);
vars.declareVariable("d", new String[] { "a", "b" });
vars.declareVariable("integer", new Integer(1));
vars.declareVariable("nan", new Double(Double.NaN));
vars.declareVariable("x", null);