Call a javascript from java step by step

Question

Is there a way to execute a java script from within a java program in a step-by-step manner?

I know how to call javascript from java. I know about Rhino or Beanshell. No web server involved.

What I'm trying to achieve: Have multiple scripts execute semi concurrently scheduled by a scheduler where each script gets a 'tick' every now and then in which it executes one atomic command just like in a debugger. This should also 'step into' functions and for/while loops.

I need to call the script 'tick' at a specific time (and return immediately) so real threads are no use.

So I guess i want a way to debug a script from within a java program without a debugger (and its overhead) involved. Just stepwise execution is needed.

Any ideas?

U mean calling Javascript from Java? Use Rhino if this is the case — Met
– Met, Commented Feb 16, 2012 at 8:44
You mean call JavaScript on the web site or just execute Javascript script from java? — Łukasz Rżanek
– Łukasz Rżanek, Commented Feb 16, 2012 at 8:44
What do you mean by "This should also 'step into' functions and for/while loops." ? — Sapan Diwakar
– Sapan Diwakar, Commented Feb 16, 2012 at 8:48
To be more precisely: I know how to call javascript from java. I know about Rhino or Beanshell. The point of interest is the tick of execution. — DerTroglodyt
– DerTroglodyt, Commented Feb 16, 2012 at 8:58

algolicious · Accepted Answer · 2012-02-16 08:48:58Z

3

Yes, it is possible by using an interpreter. More specifically, you need an JavaScript interpreter that can be executed on the JVM. Rhino seems to be the most popular one.

http://www.mozilla.org/rhino/

If you are running scripts concurrently then you will need an interpreter for each concurrent script.

answered Feb 16, 2012 at 8:48

algolicious

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4 Comments

DerTroglodyt Over a year ago

I edited my post to reflect that i already know about Rhino. My question is a little more specific. Any ideas on the tick?

algolicious Over a year ago

Ok, that is going to be a bit tricky and pretty sure that functionality isn't provided in its API. You will need to edit the source code of the JavaScript interpreter by adding some volatile flag to instruct to interpret the next JavaScript command. Your tick will need to set the flag to true and then you will need the interpreter to set the flag to false after reading interpreting a statement and then it needs to wait for the flag to be set to true.

DerTroglodyt Over a year ago

I hoped for a simpler way but expected something like that :-( I will look into this when I find the time. Thanks anyway.

algolicious Over a year ago

I don't think it will be that difficult. Otherwise you could look at the implementation of its debugger (mozilla.org/rhino/debugger.html) and replicate so its operations can be invoked from code rather than from GUI events.

Eric · Accepted Answer · 2016-12-16 04:36:09Z

0

Check out these links:

https://www.mozilla.org/rhino/tutorial.html https://blogs.oracle.com/blue/entry/scripting_with_servlets_rhino_part

They will help u get started.

edited Dec 16, 2016 at 4:36

Eric

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answered Feb 16, 2012 at 8:54

Met

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2 Comments

DerTroglodyt Over a year ago

Sorry I don't see how that helps. Besides: no web server involved.

Met Over a year ago

I thought u did not know how to use Rhino. I mean you edited your question after my post if I am not wrong. Anw no problem man.

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