I think I found the issue with this modified script.
var WebEngine = Java.type("javafx.scene.web.WebEngine");
var engine = new WebEngine();
var window = engine.executeScript("window");
print(Debug.getClass(window.foo));
print("typeof(window.foo) = " + typeof(window.foo));
if (window.foo) {
print("window.foo is truthy");
}
We need to run with -J-Dnashorn.debug to enable nashorn debug mode.
Debug.getClass gets the Java class of the value. Apparently, browser's
JSObject impl. returns a string with the value "undefined" for undefined
values! And not a special value or null for undefined...
I think nashorn's BrowserJSObjectLinker has to probably call
JSObject.hasMember to check existence of a member before calling
JSObject.getMember. That appears to be the only way to find out if
"undefined" string is due to missing property or not.
-Sundar
On Friday 27 March 2015 06:22 PM, A. Sundararajan wrote:
Browser's DOM objects (like WebEngine's) implement
netscape.javascript.JSObject interface. Such objects are treated
specially by nashorn's linker.
http://hg.openjdk.java.net/jdk9/dev/nashorn/file/ca150ddd536e/src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/linker/BrowserJSObjectLinker.java
is the dynalink linker that handles such objects. JSObject.getMember,
putMember, call are used to provide property, call access seamlessly.
Please check out this example:
http://hg.openjdk.java.net/jdk9/dev/nashorn/file/ca150ddd536e/samples/browser_dom.js
So, what you're seeing is a bug in the way that linker works. Let me
check out and file a bug.
Thanks,
-Sundar
On Friday 27 March 2015 04:41 PM, David P. Caldwell wrote:
So it's very cool, and unexpected, that JavaScript objects obtained
from a JavaFX WebEngine show up as something like ordinary Nashorn
objects in Nashorn scripts. That's an unexpected bonus (I was planning
on using .setMember() and all that stuff from
netscape.javascript.JSObject).
The objects behave a bit strangely, though. So I've got a couple of
bug reports, I guess.
Here's a script that demonstrates the ones I've found so far:
var WebEngine = Java.type("javafx.scene.web.WebEngine");
var engine = new WebEngine();
var window = engine.executeScript("window");
print("foo = " + window.foo);
print("typeof(window.foo) = " + typeof(window.foo));
if (window.foo) {
print("window.foo is truthy");
}
Output:
$ /usr/lib/jvm/jdk1.8.0_40/bin/jjs -fx nashorn.js
foo = undefined
typeof(window.foo) = string
window.foo is truthy
I actually am using a much more complicated embedding that is done
from Java, so I can tell you the problem is not in the implementation
of the -fx flag.
Other than that, I can't see much; I haven't delved into the Nashorn
code, let alone whatever magic enables this.
-- David.
