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From "Rahul Akolkar (JIRA)" <j...@apache.org>
Subject [jira] Commented: (JEXL-60) Refactor o.a.c.jexl.util and o.a.c.jexl.util.introspection
Date Sat, 01 Aug 2009 01:08:15 GMT

    [ https://issues.apache.org/jira/browse/JEXL-60?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12737804#action_12737804
] 

Rahul Akolkar commented on JEXL-60:
-----------------------------------

Just noticed that JEXL-43 is open for the 2.0 language reference and docs, so that patch should
go there.


> Refactor o.a.c.jexl.util and o.a.c.jexl.util.introspection
> ----------------------------------------------------------
>
>                 Key: JEXL-60
>                 URL: https://issues.apache.org/jira/browse/JEXL-60
>             Project: Commons JEXL
>          Issue Type: Improvement
>    Affects Versions: 2.0
>            Reporter: Henri Biestro
>            Priority: Blocker
>             Fix For: 2.0
>
>         Attachments: JEXL-60.patch, jexl60.tar.gz, jexl60.tar.gz, jexl60.tar.gz, jexl60.tar.gz
>
>
> While working on JEXL-35 and looking at Cobertua reports, it appeared that some classes
in jexl.util were not really used.
> It seems that the intention in the original code line was to create specialized executors
for each type of property getters and setters but was never completed. Thus, the Uberspectimpl
was partly in charge of discovering methods which made things harder to follow and maintain.
> The patch completes the original o.a.c.jexl.util with specialized executors for {property,
map, list, duck} setters and getters as well as methods. Since 2.0 already switched the method
cache from using string as keys to using MethodKey(s), their usage has been promoted futher
up (a method key is a method name and a set of parameters - not arguments!-) so MethodExecutor(s)
benefit from their existence.
> Since it seemed natural, IntrospectionUtils code has been displaced to MethodKey since
this is where parameters type matching has to occur.
> The general method (setter & getter) discovery mechanism is reusing the original
algorithm, trying the different types and returning the first alive one (aka the first executor
for which a java.lang.method could be found).
> The patch is faithfull to the original packages however some code has migrated; most
of the Uberspectimpl code has been displaced into o.a.c.jexl.util.Introspector to keep it
as simple as possible and still derivable.
> There were also some low-hanging fruits in this whole refactoring:
> The AST nodes (now JexlNode & SimpleNode) carry a volatile value field that allows
to use them as cache for executors; this improves performance and allows no locking concurrency.
Since we are creating executors, we might as well reuse when possible.
> The Info (debugging info) has been put to use so Jexl can create more meaningfull error
message when they occur; putting the JexlEngine in debug mode will make warning/exception
messages report their point of creation (file or url for scripts, method for expression).
> And a 'new' function/operator has been implemented so Jexl can now instantiate objects
as well.
> It is a huge and worrysome patch but the Checkstyle & Corbertua reports look pretty
good. 
> The following classes need to be removed *before* applying the patch:
> src/java/org/apache/commons/jexl/parser/JEXLNode.java
> src/java/org/apache/commons/jexl/Arithmetic.java
> src/java/org/apache/commons/jexl/util/PropertyExecutor.java
> src/java/org/apache/commons/jexl/util/BooleanPropertyExecutor.java
> src/java/org/apache/commons/jexl/util/introspection/IntrospectionUtils.java
> src/java/org/apache/commons/jexl/util/introspection/UberspectLoggable.java
> src/java/org/apache/commons/jexl/util/GetExecutor.java
> The pom.xml has been modified to use a newer version of the javacc plugin.

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