Caching and re-using bindings

[yikes aroni]

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
>>
>