Re: [Bsf4oorexx-devel] Ad JSR-223 implementation in BSF4ooRexx ...

[Rony G. F. <Ron...@wu...>]

Hmm, an additional info, a correction.

On 11.06.2015 18:42, Rony G. Flatscher wrote:
> Hi there,
>
> thought, for archival purposes at least :), that I sketch the reasonings that stood behind the
> implementation of JSR-223 ("javax.script") in BSF4ooRexx. The JSR-223 implementation is now
> considered to be complete, the latest beta of BSF4ooRexx () contains it. You will find examples in
> Java and NetRexx that employ this support for ooRexx in the directories
> "bsf4oorexx/samples/NetRexx/jsr223" and "bsf4oorexx/samples/Java/jsr223".
>
> A remark: I was one of the members of the "Java Specification Request" group # 223 ten years ago.
> As such I was able to influence the architecture a little bit. The technical lead, a then Sun
> employee, Mike Goran, was engaged in experimenting with adding support for PHP in the context of
> JSP and the like, so this environment had its influences a little bit, the other one came (e.g.
> through myself) from the Apache Software Foundation (ASF) "Bean Scripting Framework (BSF)", which
> I use in BSF4ooRexx (that's where "BSF" comes from).
>
> Ad JSR-223: the specifations can be found and downloaded from
> <https://jcp.org/aboutJava/communityprocess/final/jsr223/index.html>. The implementation in Java
> took first place with Java 6 (Java 1.6) in the package "javax.script". Currently, Java 8 (Java
> 1.8) is the latest official release of Java, hence here the link to its documentation
> <https://docs.oracle.com/javase/8/docs/api/index.html?javax/script/package-summary.html>. Please
> consult this documentation, if interested in details.
>
>   * javax.script.ScriptEngine: one needs to implement this interface, which is responsible for
>     evaluating scripts, supplying data to the scripts using the javax.script.ScriptContext
>     interface functionality and fetching any return values from such scripts.
>       o To ease the implementation of script engines, there is a partially implemented (abstract)
>         class that one can extend: javax.script.AbstractScriptEngine
>       o The org.rexxla.bsf.engines.rexx.jsr223.RexxScriptEngine class extends the
>         AbstractScriptEngine.
>           + This class implements the Compilable and Invocable interfaces as well.
>           + In addition it defines a method named "RexxCompiledScript getCurrentScript()" that
>             returns the compiled (actually the initialized routine object from the latest run) script.
>           + As long as no script has been evaluated/run by the RexxScriptEngine instance yet, it
>             is possible to configure the associated ooRexx interpreter to your needs, by using the
>             method "public org.rexxla.bsf.engines.rexx.RexxEngine getBsfRexxEngine()"; cf. samples
>             in "bsf4oorexx/samples/NetRexx/handlers" and "bsf4oorexx/samples/Java/handlers"
>
>   * The ScriptContext maintains instances of classes that implement the javax.script.Bindings
>     interface at the ScriptContext.ENGINE_SCOPE and/or the ScriptContext.GLOBAL_SCOPE. Note these
>     scopes have well defined, numeric values, ENGINE_SCOPE the value 100, GLOBAL_SCOPE the value
>     200. In theory it is possible to define any additional number of bindings by using different
>     numeric values for "scope".
>       o To ease the implementation of script engines, there is an implementation of the Bindings
>         interface: javax.script.SimpleBindings
>       o To ease the implementation of script engines, there is an implementation of the
>         ScriptContext interface: javax.script.SimpleScriptContext which employs
>         javax.script.SimpleBindings
>
>   * javax.script.ScriptEngineFactory: this interface must be implemented.
>       o The org.rexxla.bsf.engines.rexx.jsr223.RexxScriptEngineFactory implements this interface.
>
>   * javax.script.Invocable: this interface is optional.
>
Addtional REMARK:

      * javax.script.Invocable: this interface is optional.
          o implemented by org.rexxla.bsf.engines.rexx.jsr223.RexxScriptEngine
          o implemented by org.rexxla.bsf.engines.rexx.jsr223.RexxCompiledScript

>   * javax.script.Compilable: this interface is optional.
>
CORRECTION:

      * javax.script.Compilable: this interface is optional.
          o implemented by org.rexxla.bsf.engines.rexx.jsr223.RexxScriptEngine


  * javax.script.CompiledScript
      o To ease the implementation of script engines, there is a partially implemented (abstract)
        class that one can extend: javax.script.CompiledScript
      o The org.rexxla.bsf.engines.rexx.jsr223.RexxCompiledScript extends this abstract class.
          + RexxCompiledScript implements the Invocable interface


> The RexxScriptEngine will always compile the supplied script, caches it ("state of the script
> engine") and invokes the "Object eval(ScriptContext)" method on it.
>
> If the same script source gets supplied again, then the RexxCompiledScript is reused, by supplying
> the actual ScriptContext which should be employed in its ".eval(Scriptcontext)".
>
> Any invocation from Invocable() methods will cause the appropriate Invocable methods in the
> compiled script (fetched with "RexxCompiledScript RexxScriptEngine.getCurrentScript()") to be
> executed. Due to the BSF4ooRexx implementation the Invocable methods  "public Object
> invokeMethod(Object thiz, String name, Object... args)" and "public <T> T getInterface(Object
> thiz, Class<T> clasz)" are implemented (and used by RexxCompiledScript objects) in
> RexxScriptEngine, the other Invocable methods are used with their RexxCompiledScript implementations.
>
> The JSR-223 samples that demonstrate how to use the "javax.script" functionality (together with
> the Rexx scripts they employ) from NetRexx and Java can be found
> "bsf4oorexx/samples/NetRexx/jsr223" and "bsf4oorexx/samples/Java/jsr223".
>
> A concluding hint: the "bsf4oorexx/samples" directories all have a file named "index.html" which
> briefly explains the samples stored in the directory they belong to.
>
> ----
>
> If there are any questions, please come forward and ask them!
>
> ---rony
Sorry for any inconvenience.

---rony