Inconsistent missing property handling with java objects

Hannes Wallnoefer hannes.wallnoefer at
Wed Sep 3 15:00:58 UTC 2014

Hi Mike,

It was just a design decision to handle missing Java properties this way 
in Nashorn.

The behaviour is implemented in NashornBottomLinker.linkBean method. 
Unfortunately there's currently no way to configure Nashorn to behave 
the way you want it to.


Am 2014-09-03 um 16:13 schrieb Mike Rettig:
> With nashorn, it seems that the assignment and accessing of missing
> properties on java objects is handled as 'undefined'.
> Example:
>          String engine = "nashorn";
>          ScriptEngineManager engineManager =
>                  new ScriptEngineManager();
>          final ScriptEngine nashorn = engineManager.getEngineByName(engine);
>          nashorn.eval("var d=new java.util.Date();");
>          nashorn.eval("d.badProp=1233");
>          nashorn.eval("print(d.badProp)");
> This will print 'undefined'. It doesn't fail on the 'badProp' on the Date
> object. With Rhino, this would fail on the assignment of the bad property
> with the following error:
> "Exception in thread "main" javax.script.ScriptException:
> Java class
> "java.util.Date" has no public instance field or method named "badProp".
> (<Unknown source>#1) in <Unknown source> at line number 1"
> I want the script to fail when the bad property is referenced.  I've tried
> 'use strict', the rhino compatibility script, and attempting to define
> __noSuchProperty__
> on the java object. I can create a wrapper object that simply delegates to
> the java object and throws if a property is undefined, but that seems
> excessive.
> Is this the correct behavior? Is there a way to work around this behavior
> in nashorn?
> Thanks,
> Mike

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