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From wolfgang häfelinger <whaefelin...@gmail.com>
Subject Re: Reasons why Java 7 got me excited about Ant 2
Date Sun, 26 Feb 2012 12:47:24 GMT
Hi there,

how about rewriting Ant 2.0 using Scala? Scala appears to be well
suited as a scripting language. Charged with a scripting language, I
could write low level macros on the fly.


// Wolfgang


On Fri, Feb 17, 2012 at 2:31 AM, Bruce Atherton <bruce@callenish.com> wrote:
> I thought I'd expand on why I got so excited about NIO 2.0 and JSR 203 as
> well as the other changes in Java 7. I can see I have done a bad job of
> selling the benefits of a refactoring for potential volunteers. Reading
> through the changes that were introduced in Java 7, it seems to me that Ant
> was probably an inspiration for a lot of them.
>
> Others come from taking the performance of I/O on Java more seriously. This
> has the potential to speed Ant up enormously. Projects like Tim Bray's Wide
> Finder 2[1] showcased just how badly Java performed and benchmarks like that
> may have been an impetus to focus resources on taking advantage of all the
> features of the native filesystems. Unfortunately the results of the project
> are lost due to Oracle's acquisition of Sun, but you can still see the
> results from the original Wide Finder 1[2] although there isn't even an
> attempt to do a Java implementation there. I can tell you from memory that
> the final results on WF2 were several C implementations with innovative I/O
> using parallel processing at the top, erlang and ruby and scala were up
> there, but the fastest Java implementation was in the double digits in the
> list as I recall.
>
> The basics for file handling in Java 7 are provided by Path and the Paths
> Utility class, along with the FileSystemProvider classes. If Ant 2 were
> created to make Resource a fundamental element and Path the Resource that
> represented something on a file system (native file systems, zip/jar file
> systems, and I expect eventually open source projects will add others like
> HTTP, FTP, NFS and Samba), I think the LOC count on Ant could be reduced
> tremendously. Writing patches would be simplified and contributing to Ant
> would have a lower barrier to entry for new people coming in. Path is
> immutable which suits Ant well. Path has methods to access elements in a
> file path, compare, test, normalize, and relativize paths in the ways that
> Ant has code to do. It has all kinds of features for determining
> accessibility on the native filesystem and bulk loading file metadata
> attributes whereas currently it is done one field at a time. Symbolic link
> identification and handling is a core feature. And converting to and from
> File objects is trivial.
>
> Add to that the new methods on File. There is also a Files utility helper
> class. Files covers the most basic tasks in Ant implemented using all the
> features of the native filesystem to make them as fast as possible: copying;
> deleting; moving; reading file contents; writing; creating directories, file
> and links; getting input and output streams. There is also recursion with a
> method for walking a file tree that creates a FileVisitor interface
> implementation, either default or custom, with 3 phases: previsit directory,
> visit file, and postvisit directory. It also provides for a visit file
> failed method. At each point you can continue, stop, skip subtree, or skip
> other entries in the current directory. Options control whether symlinks are
> followed, and cycles are detected.
>
> DirectoryStream includes filters like glob, regex, and custom
> implementations that could be perfect for implementing Selectors.
> DirectoryStream uses less resources and works much better with remote
> resources. It also handles directories that are very large much more
> efficiently.
>
> Error handling throughout is by exception rather than boolean value as it is
> now, which I'm sure we all agree is preferable.
>
> Then there is the Watch Service which uses the native eventing service if
> available, where you can get events in your build when a file is created or
> deleted, or when a directory is modified. Would we translate it into
> something for BuildListeners? How would we harness it, scheduling a target
> and its dependencies when the a watch fired an event?
>
> I could keep going  but this is getting rather long. I'll just point out a
> few resources from other people that are clearer than I am and have more
> detail: The Java 7 feature list[3] is comprehensive but has little on the
> impact of features; this Doctor Dobbs post[4] has good code examples for how
> NIO 2 could be used by Ant; an article listing "8 things I found most
> useful"[5], all of which are relevant to a simplified Ant implementation,
> details the NIO 2 changes at #8; interviews with Alan Bateman in text[6],
> video[7], and podcast[8] are interesting, as is a JavaOne 2011 slide
> show[9];  Leandro Pezzente sent me a link[10] (thanks, Leandro) that lists
> some of the other changes to Java 7 to think about, although it only
> mentions the file system changes that JSR 203 introduces in passing.
>
> [1] http://www.tbray.org/ongoing/When/200x/2008/05/01/Wide-Finder-2
> [2] http://www.tbray.org/ongoing/When/200x/2007/10/30/WF-Results
> [3] http://openjdk.java.net/projects/jdk7/features/#f250
> [4] http://drdobbs.com/blogs/jvm/231600403
> [5] http://jaxenter.com/java-7-the-top-8-features-37156.html
> [6] http://www.artima.com/lejava/articles/more_new_io.html
> [7] http://www.youtube.com/watch?v=yNRS1ssLPdQ
> [8]
> https://blogs.oracle.com/javaspotlight/entry/java_spotlight_episode_59_alan
> [9] http://openjdk.java.net/projects/nio/presentations/TS-5052.pdf
> [10]
> http://marxsoftware.blogspot.com/2011/03/jdk-7-new-interfaces-classes-enums-and.html
>
>
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-- 
Wolfgang Häfelinger

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