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https://issues.apache.org/jira/browse/JEXL-197?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15362455#comment-15362455
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Dmitri Blinov commented on JEXL-197:
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Putting the JEXL-185 aside, the first impression is yes, that is what I need.
Now as I'm in the process of adopting this, I think some other issues may
arise, likes JEXL-201, but again - in principle yes, great extensibility point
and great job, many thanks. As for JexlContext, first I was a little puzzled
why it was put in JexlContext but not in JexlArithmetic for example, where
major part of customization code is to be placed, but now I'm starting to think
it's even better that way, since annotations may have access to JexlContext
internal structures.
> Add annotations
> ---------------
>
> Key: JEXL-197
> URL: https://issues.apache.org/jira/browse/JEXL-197
> Project: Commons JEXL
> Issue Type: Improvement
> Reporter: Dmitri Blinov
> Assignee: Henri Biestro
> Fix For: 3.1
>
>
> Follow up from JEXL-194...
> As an implementation to the extension of statement executions in JEXL we
> could introduce the use of annotations to each statement or block in the
> script, i.e.
> {code}
> @synchronized(items) {for (x : items) ...}
> {code}
> Each statement block should be allowed to have only one annotation but it
> would be convenient to allow the syntax
> {code}
> @silent @lenient {null.tryMe()}
> {code}
> which should be syntaxically equivalent to:
> {code}
> @silent {@lenient {null.tryMe()}}
> {code}
> From the JexlEngine point of view, each annotation could be implemented in
> the form of Interceptor interface, for example
> {code}
> public interface Interceptor {
> public Object onExecute(JexlStatement block, String annotation, Object..
> args);
> }
> {code}
> The annotation syntax should allow for zero, one or more parameters. Those
> parameters should be evaluated before interceptor execution and submitted to
> the Interceptor.onExecute() method via args parameter.
> JexlEngine should be given a method to register annotation interceptor based
> on annotation name, and the one for default interceptor, which should be
> called before each statement execution as if @default annotation is declared
> in each statement in script.
> {code}
> @silent {@default {...}}
> {code}
> The JexlStatement is the proposed new interface to somehow identify the
> statement or block of code which may also provide some info about it's stack
> frame.
> {code}
> public interface JexlStatement {
> public Object interpret();
> // ..
> }
> {code}
> The JexlStatement.interpret() method should trigger the execution of the
> statement block, returning statement's result as its return value.
> In the absence of a matching interceptor corresponding to the annotation
> name, JexlEngine should simply ignore that, or write some diagnostic message
> in the log file.
> Such implementation could provide developers with excellent tool to add
> various checks and enhancements to scripting without pushing for new features
> that eventually would mess up the basic code. The JEXL-185 issue could also
> be dropped since tracing could be added easily via interceptors.
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