Nęste |
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Planche 3 |
Ant |
Ant is a Java based build tool. In theory it is kind of like make
without make's wrinkles.
Why another build tool when there is already make, gnumake, nmake, jam,
and others? Because all of those tools have limitations that Ant's
original author couldn't live with when developing software across
multiple platforms. Make-like tools are inherently shell based. They
evaluate a set of dependencies and then execute commands not unlike what
you would issue on a shell. This means that you can easily extend these
tools by using or writing any program for the OS that you are working
on. However, this also means that you limit yourself to the OS, or at
least the OS type such as Unix, that you are working on.
Makefiles are inherently evil as well. Anybody who has worked on them
for any time has run into the dreaded tab problem. "Is my command not
executing because I have a space in front of my tab!!!" said the
original author of Ant way too many times. Tools like Jam took care of
this to a great degree, but still use yet another format to use and
remember.
Ant is different. Instead of a model where it is extended with shell
based commands, it is extended using Java classes. Instead of writing
shell commands, the configuration files are XML based calling out a
target tree where various tasks get executed. Each task is run by an
object which implements a particular Task interface.
Granted, this removes some of the expressive power that is inherent by
being able to construct a shell command such as `find . -name foo -exec
rm {}` but it gives you the ability to be cross platform. To work
anywhere and everywhere. And hey, if you really need to execute a shell
command, Ant has an exec rule that allows different commands to be
executed based on the OS that it is executing on.