// create our factory which uses our customized builder
System.setProperty("javax.el.nullProperties", "true");
ExpressionFactory f = new ExpressionFactoryImpl(System.getProperties());
// create our context
ELContext context = new SimpleContext();
// create our expression we want to evaluate
ValueExpression e = f.createValueExpression(context, "${map[null]}", String.class);
// create a map containing a value for key <code>null</code> and make it available
Map<String, String> map = new HashMap<String, String>();
map.put(null, "foo");
context.getELResolver().setValue(context, null, "map", map);
// let's go...
System.out.println(e.getValue(context)); // --> "foo"
}