Caching and re-using bindings

[yikes aroni]

Hmm.... it works if i instantiate the SimpleBinding obj and then putAll the
bindings from the original bindings obj.

Bindings bSimple = new SimpleBindings();
bSimple.putAll(bEngine);

Otherwise they either remain the same object or are bound in some way s.t.
changes to bEngine are in bSimple. This just seems strange to me. Still
curious to know what the reason for this is, despite having found a
workaround.



On Tue, Dec 6, 2016 at 7:59 AM, yikes aroni <yikesaroni at gmail.com> wrote:

> Thanks for your response Edmond -- the problem is that a simplebindings
> object still gets all the changes to the original bindings.... see below:
>
> // put variable globalA into the ScriptContext.ENGINE_SCOPE bindings
> se.eval("globalA = 'testA';");
> // Snapshot the bindings from the engine.
> Bindings bEngine = se.getBindings(ScriptContext.ENGINE_SCOPE );
> // print the bindings to confirm there is only one variable in them. -->
> TRUE
> printBindings(bEngine);
> ------------------------
> globalA = testA
> // At this point there is only 'globalA' in the bindings so instantiate
> simplebindings:
> Bindings bSimple = new SimpleBindings(bEngine);
> // Verify by printing the bindings
> printBindings(bSimple);
> ------------------------
> globalA = testA
> // put variable globalB into the ScriptContext.ENGINE_SCOPE bindings
> se.eval("globalB = 'testB';");
> // print the bindings. Now both variables are present........... WHY???
> printBindings(bEngine);
> ------------------------
> globalA = testA
> globalB = testB
> // But look -- they are in the simple bindings obj as well!
> printBindings(bSimple);------------------------
> globalA = testA
> globalB = testB
>
> That's precisely what i don't get --> Why are variables added to the
> engine bindings *after* instantiating the simpleBindings showing up in the
> simpleBindings object?
>
> And how do i avoid that?
>
> thanks
>
> On Mon, Dec 5, 2016 at 3:01 PM, Edmond Kemokai <ekemokai at gmail.com> wrote:
>
>> Why don't you create instances of SimpleBinding and use those as needed?
>> Use ScriptEngine.setBindings to reset the binding...
>>
>> On Dec 5, 2016 1:36 PM, "yikes aroni" <yikesaroni at gmail.com> wrote:
>>
>>> I want to cache ScriptEngine bindings for reuse. The basic algo would be
>>>
>>> 1) Build up my ScriptEngine (SE) with stuff i need.
>>> 2) Snapshot the bindings -- i.e., cache them
>>> Use engine.getBindings(ScriptContext.ENGINE_SCOPE)
>>> 3) Use the SE for stuff that might modify its state.
>>> 4) When done, replace the SE's bindings with my snapshotted bindings
>>> Use engine.setBindings(_bindings_, ScriptContext.ENGINE_SCOPE)
>>> 5) I now have a "fresh" SE to use.
>>>
>>> The problem is that this doesn't work as expected. The cached bindings
>>> appear to point to the actual SE bindings and therefore whatever gets
>>> added
>>> to the SE bindings, also gets added to the cached bindings. Here's some
>>> code to show how it's not doing what i would expect.
>>>
>>> public class TempEngineTest {
>>>
>>> static ScriptEngineManager seManager = new ScriptEngineManager();
>>> static ScriptEngine se = seManager.getEngineByName("nashorn");
>>> public static void printBindings(Map<String, Object> bindings) {
>>> for (Map.Entry<String, Object> entry : bindings.entrySet()) {
>>>    System.out.println(entry.getKey() + " = " + entry.getValue());
>>> }
>>> }
>>> public static void main(String[] a) throws Exception {
>>> // put variable globalA into the ScriptContext.ENGINE_SCOPE bindings
>>> se.eval("globalA = 'testA';");
>>> // Snapshot the bindings from the engine.
>>> Bindings bEngine = se.getBindings(ScriptContext.ENGINE_SCOPE );
>>> // print the bindings to confirm there is only one variable in them. -->
>>> TRUE
>>> printBindings(bEngine);
>>> // put variable globalB into the ScriptContext.ENGINE_SCOPE bindings
>>> se.eval("globalB = 'testB';");
>>> // print the bindings. Now both variables are present........... WHY???
>>> printBindings(bEngine);
>>> }
>>> }
>>>
>>> I've seen suggestions to cache and reuse bindings in various articles,
>>> but
>>> no specific code for doing so. How do i accomplish this in actual code?
>>>
>>> thanks
>>>
>>
>