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List:       velocity-dev
Subject:    [jira] Updated: (VELOCITY-742) Easily Add/Remove/Replace Directives
From:       Jarkko_Viinamäki_(JIRA) <dev () velocity ! apache ! org>
Date:       2009-12-23 10:29:29
Message-ID: 1604979320.1261564169523.JavaMail.jira () brutus
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     [ https://issues.apache.org/jira/browse/VELOCITY-742?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel \
]

Jarkko Viinamäki updated VELOCITY-742:
--------------------------------------

    Attachment: velocity-742.patch

OK. This patch now provides two new public methods in VelocityEngine and Velocity \
classes:

removeDirective(String name)
loadDirective(String className)

Note that all parser instances use the same set of directives so it's not possible to \
disable e.g. #include directive for certain page rendering but still keep it active \
for other possibly concurrent page renderings. Note also that you need to first call \
init on Velocity or VelocityEngine before you start removing directives (otherwise \
the autoinit "overwrites" the removal operation). See the Velocity742TestCase.

Note! After applying the patch, you need to run "ant parser test" in order to update \
the generated Parser.java and other related classes.

--

I also noticed that there was a hidden bug in the code: RuntimeInstance keeps a map \
of directives in variable called runtimeDirectives. When a new parser was created \
that variable was passed to the Parser but the parser made a HashMap copy of the \
runtimeDirectives (this was one of the speed improvements since it slows things down \
if many parsers hammer the same synchronized map).

Therefore when addDirective, removeDirective etc. were called in RuntimeInstance, \
they had no effect since all the created parsers still had a copy of the old \
runtimeDirectives map.

I fixed it so that Parser instances do not have a copy of the directives map at all. \
Instead, they redirect e.g. getDirective and isDirective calls to RuntimeInstance \
which uses unsynchronized HashMap for the lookups. When the runtimeDirectives map is \
modified (new directive is added or an old one is deleted), a new HashMap is created \
as a copy and the reference is updated so that subsequent calls to \
RuntimeInstance.getDirective use the newly created map (Copy-on-Write pattern I \
guess).

Nathan & others, please take a look at this when you have time and check if I did \
something really silly.

Merry Christmas! :)

> Easily Add/Remove/Replace Directives Without Cracking Open Velocity Jar
> -----------------------------------------------------------------------
> 
> Key: VELOCITY-742
> URL: https://issues.apache.org/jira/browse/VELOCITY-742
> Project: Velocity
> Issue Type: New Feature
> Components: Engine
> Affects Versions: 1.6.2
> Reporter: Tim White
> Priority: Minor
> Attachments: velocity-742.patch
> 
> 
> There are two use cases that I have for this issue:
> 1) We need to turn off #include in order to parse .html files that include SSI \
> directives:  <!--#include virtual=""-->  (we always use #parse in our world, so no \
> loss for #include going away) 2) We need to supply our own version of #parse that \
> contains the development hooks that I described in a different issue. Right now, \
> the only crisp way to do is is to crack open the velocity .jar and make these \
> changes, which is very risky, because future developers may upgrade to new versions \
> of Velocity and not realize that there are customizations and/or not understand how \
> to remake them....not to mention in a shared-classpath environment, we don't always \
> have control over which copy of the Velocity .jar we're using. Ideally, there would \
> be config options like this: directive_remove ("#parse", "#include")
> directive_add ("#parse", "com.qwest.velocity.directives.Parse")
> Thanks!
> Tim

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