I've added support for the SCXML Script Module to the J6 branch and addressed the JEXLContext shortcomings (wasn't designed for scripts) as discussed below.
Here are a couple of simple test case documents using inline scripts: JEXL: http://svn.apache.org/repos/asf/commons/proper/scxml/branches/J6/src/test/java/org/apache/commons/scxml/env/jexl/script-01.xml JavaScript: http://svn.apache.org/repos/asf/commons/proper/scxml/branches/J6/src/test/java/org/apache/commons/scxml/env/javascript/script-01.xml -Rahul On Tue, Dec 16, 2008 at 6:22 PM, Rahul Akolkar <rahul.akol...@gmail.com> wrote: > As a reminder, Commons SCXML does not support the SCXML Script Module > yet, since its not required (the required bits get more attention :-). > However, thats mainly a matter of prioritization, so if such support > becomes available it can surely be added. > > At the crux of the issue, there are two options: > (1) The elegant way to add this support requires an additional method > to the Evaluator interface (say, evalScript) and that breaks backward > compatibility. > (2) Alternatively, we can create an extended Evaluator interface that > handles scripts (and then check whether the Evaluator implementation > supports this extended interface at the point where scripts are > executed -- or throw up in some reasonable fashion otherwise) > > Given we're in 0.x releases, (1) might still be OK and is definitely cleaner. > > To your questions ... > > On Tue, Dec 16, 2008 at 5:40 PM, Ingmar Kliche > <ingmar.kli...@googlemail.com> wrote: >> I tried to use the o.a.c.s JEXL Context/Evaluator with an implementation of >> the <script> element. I want to make the <script> implemenation independent >> of the expression languange. But unfortunately it seems to me that EL is not >> useful (e.g. does not support assignments) and Jexl has some shortcomings: >> >> 1) I tried a script with multiple statements, like: >> >> <script> >> x = y; >> y = 3; >> </script> >> >> While executing this script I get: >> >> WARNUNG: The JEXL Expression created will be a reference to the first >> expression from the supplied script: " >> x = y; >> y = 3;" >> >> Does the JEXL implementation not support multiple statements per expression? >> > <snip/> > > It does, but you have to use the ScriptFactory (as against using > ExpressionFactory) -- ties into comment above regarding a new > Evaluator#evalScript() method. > > >> 2) Unfortunately the o.a.c.s JexlEvaluator#eval() generates an >> "effectiveContext" (to implement the scope chain) and passes it to the JEXL >> expression for execution. Thus any modification taken by the script (like >> any assingments as "x = y") will modify the "effectiveContext", not the >> actual state context. After executing "x=y", "x" remains unchanged within >> the states context. >> >> Is the JexlContext implemenatation useful for a <script> implementation at >> all from this perspective? >> > <snap/> > > Correct, the out of the box implementation isn't conducive to scripts > (writes aren't supported since those are handled via <assign>, for > example). When we make the other changes to accomodate <script>, we > will have to address this. > > Interim, it should be possible to implement script as a custom action > (which is probably what you're doing here) and use your own evaluator > implementation (similar to the extended one mentioned above) which the > custom action leverages. > > -Rahul > > >> - Ingmar. >> > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
