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From Wascally Wabbit <wascallywab...@earthling.net>
Subject The difficulty of extending Ant with large Antlibs because...
Date Sat, 17 Mar 2007 22:41:35 GMT
Hi all,

A bit of frustration...

I've just begun upgrading my antlibs to Ant 1.7 and I'm just blown 
over by the number of changed assumptions that are now part of base 
classes like Task and UnknownElement. It's just surprising coming 
from a 0.5 revision change. It's becoming harder and harder to 
upgrade with Ant for large antlib collections (IMO) because of the 
lack of a clear lifecyle structure for data types and tasks (and task 
containers and probably AntLibDefinitions too).

Some examples:

+ With Ant 1.7 the inability to execute the same task twice (even if 
_you've written it do handle this_)...UE was altered and now this 
line breaks (from lines 291:296). UE is one of the great mysteries of 
Ant for a extension developer:

    // Finished executing the task, null it to allow
    // GC do its job
    // If this UE is used again, a new "realthing" will be made
    realThing = null;
    getWrapper().setProxy(null); //OUCH!OUCH!OUCH!

If Task.maybeConfigure is called subsequently it promptly throws a 
NPE because it uses the proxy w/o checking for null.

+ With Ant 1.7 a complete reversal of the ordering of attribute 
configuration relative to child configuration...it's not the 
switching that's the fundamental problem (implementation details and 
all that) but Ant lacks any sort of public lifecycle event that a 
Task or TaskContainer implementation can consistently count on from 
release to release. It's always an adventure...even between minor 
minor revisions. It's even possible for a Task's "init()" method to 
be called multiple times...

Perhaps there could be a clear "I'm configured" trigger or event or 
callback or method or something before the task's execute method is called.

+ Perhaps DataTypes can also have the ability to know when they've 
been completely configured (from Ant's perspective)? I guess this is 
more of the same lack-of lifecycle transparency as is the case for 
Tasks. I often use "quiet" tasks to get these features, but this is a 
heavy-handed solution.

Ok...now I go back to upgrading...


The Wabbit 


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