Nashorn: Javascript to Java call question

[A. Sundararajan]

Hi Mani,

You need to *override* nashorn.jar in the underlying jdk8 build. The 
command line for the same is as follows:

  /usr/lib/jdk1.8.0/bin/java 
-Djava.ext.dirs=<$nashorn/dist-dir-of-your-nashorn-repo> JSObjectTest

With that nashorn.jar from the latest (nashorn repo) code is used - 
rather than the nashorn.jar bundled in jdk8. Note that this issue will 
be resolved in a (near) future jdk8 snapshot build (and also in jdk8 
fcs). For the interim period, you've to use the above command line.

Hope this helps,
-Sundar

On Saturday 08 June 2013 12:33 AM, Mani Sarkar wrote:
> Thanks Sundar, Jim for the explanation.
>
> I extracted the jsobjectTest() from ScriptEngineTest.java as it is and
> compiled and ran it, when I run it I still get the same error that I got
> with my example. I have put all of this in a gist to demonstrate what I was
> doing:
> https://gist.github.com/neomatrix369/5731520
>
> I also ran the ScriptEngineTest using the jtreg command and that ran
> successfully:
>
>   ~/jtreg/linux/bin/jtreg -jdk:/usr/lib/jdk1.8.0
> -Xbootclasspath/p:$HOME/sources/jdk8_tl/nashorn/dist/nashorn.jar
> -verbose:fail test/src/jdk/nashorn/api/scripting/ScriptEngineTest.java
>
> Regards,
> mani
>
> On Thu, Jun 6, 2013 at 11:25 AM, Mani Sarkar <sadhak001 at gmail.com> wrote:
>
>> Hi Jim,
>>
>> You have been very quick with your response to my query.
>>
>> Thanks for going through the trouble, apologies for the empty folders,www.google.co.in/accounts/Logout2?hl=en&service=mail&ilo=1&ils=s.IN&ilc=1&continue=https%3A%2F%2Faccounts.google.com%2FServiceLogin%3Fservice%3Dmail%26passive%3Dtrue%26rm%3Dfalse%26continue%3Dhttps%3A%2F%2Fmail.google.com%2Fmail%2F%26ss%3D1%26scc%3D1%26ltmpl%3Ddefault%26ltmplcache%3D2%26hl%3Den&zx=-1663605433tami
>> they are submodules that haven;t been pushed correctly to my repo.
>>
>> I have made the changes you suggested and rebuilt my class (I had to get
>> the latest version of the codebase as JSObject wasn;t present in
>> nashorn.jar in  my old code-base).
>>
>> After building and running I get the below:
>>
>> Exception in thread "main" java.lang.ClassCastException:
>> jdk.nashorn.api.scripting.ScriptObjectMirror cannot be cast to
>> jdk.nashorn.api.scripting.JSObject
>> at JSJSONInJava.main(JSJSONInJava.java:19)
>>
>> Lines 18 and 19 are as follows:
>> 17: // fetch the value of a variable
>> 18: Object objFromJS = engine.get("JSONObjectUsingJavaScript");
>> 19: JSObject jsonObjFromJS = (JSObject) objFromJS;
>>
>> Any ideas, or is it something new?
>>
>> Regards,
>> mani
>>
>>
>> On Wed, Jun 5, 2013 at 8:51 PM, Jim Laskey <james.laskey at oracle.com>wrote:
>>
>>> The repo you provided has empty JSON-java and JSON-js directories, so
>>> I'll give you an alternative example.  The main thing to note is that,
>>> because of a JS object's dynamic nature, it can not mirror a Java object.
>>>   A better analogy would be to think of a JS object as a Map object, where
>>> properties are keys and you access values with keys.
>>>
>>> Run the enclosed example as follows;
>>>
>>> javac Example.java
>>> java Example
>>>
>>> The class of myObject is a JSObject.  You can access properties of a
>>> JSObject with getMember/setMember (or getSlot/setSlot for integer keys.)
>>>
>>> === Example.java ===
>>>
>>> import javax.script.*;
>>> import jdk.nashorn.api.scripting.JSObject;
>>>
>>> public class Example {
>>> public static void main(String[] args) throws Exception {
>>>   ScriptEngineManager factory = new ScriptEngineManager();
>>>   ScriptEngine engine = factory.getEngineByName("nashorn");
>>>   engine.eval(new java.io.FileReader("Example1.js"));
>>>   JSObject myObject = (JSObject)engine.get("myObject");
>>>   System.out.println(myObject.getMember("a"));
>>>   System.out.println(myObject.getMember("b"));
>>>   System.out.println(myObject.getMember("c"));
>>>          myObject.setMember("d", "A new string");
>>>   engine.eval(new java.io.FileReader("Example2.js"));
>>>
>>> }
>>> }
>>>
>>> === Example1.js ===
>>>
>>> var myObject = {
>>>     a: "A string",
>>>     b: 100,
>>>     c: true
>>> }
>>>
>>> === Example2.js ===
>>>
>>> print(myObject.d);
>>>
>>> ==== Output ===
>>>
>>> A string
>>> 100
>>> true
>>> A new string
>>>
>>>
>>> Cheers,
>>>
>>> -- Jim
>>>
>>>
>>>
>>>
>>>
>>>
>>> On 2013-06-05, at 3:50 PM, Mani Sarkar <sadhak001 at gmail.com> wrote:
>>>
>>> Hi,
>>>
>>> I have another query regarding the example (see
>>>
>>> https://github.com/neomatrix369/NashornHackDay/blob/master/examples/JSON_in_JS_and_Java/JSJSONInJava.java
>>> )
>>> created sometime back  during the Nashorn hackday. When I bring a JS
>>> object
>>> created in Nashorn into Java I'm not able to access the object directly,
>>> how do I access it like a normal java object.
>>>
>>> If its a raw / primitive type then the contents are accessible (you can
>>> see
>>> the value) while for JS object, when I say
>>>
>>> *System.out.println(JSObjectFromNashorn);*
>>>
>>>
>>> I get the below output
>>>
>>> *[object object]*
>>>
>>>
>>> The full implementation of what I'm talking about can be found at the
>>> above
>>> link.
>>>
>>> Regards,
>>> mani
>>>
>>> --
>>> *Twitter:* @theNeomatrix369          *Blog:*
>>> http://neomatrix369.wordpress.com
>>> *JUG activity:* LJC Advocate (@adoptopenjdk & @adoptajsr programs)
>>> *Meet-a-Project:* https://github.com/MutabilityDetector
>>> *Bitbucket:* https://bitbucket.org/neomatrix369  * **Github:*
>>> https://github
>>> .com/neomatrix369
>>> *LinkedIn:* http://uk.linkedin.com/pub/mani-sarkar/71/a77/39b
>>> *Devoxx UK 2013* was a grand success:
>>> http://www.devoxx.com/display/UK13/Home
>>>
>>> *Don't chase success, rather aim for "Excellence", and success will come
>>> chasing after you!*
>>>
>>>
>>>
>>
>> --
>> *Twitter:* @theNeomatrix369          *Blog:*
>> http://neomatrix369.wordpress.com
>> *JUG activity:* LJC Advocate (@adoptopenjdk & @adoptajsr programs)
>> *Meet-a-Project:* https://github.com/MutabilityDetector
>> *Bitbucket:* https://bitbucket.org/neomatrix369  * **Github:* https://
>> github.com/neomatrix369
>> *LinkedIn:* http://uk.linkedin.com/pub/mani-sarkar/71/a77/39b
>> *Devoxx UK 2013* was a grand success:
>> http://www.devoxx.com/display/UK13/Home
>>
>> *Don't chase success, rather aim for "Excellence", and success will come
>> chasing after you!*
>>
>
>