Scaling to large projects

[Tim Singletary <ts...@vetinsite.com>]

I can't figure how to set up Ant so that it will scale to be usable
on a large project.  Is there an 'Ant-way-of-doing-things' that I haven't
grokked yet?

For example, suppose my source files are

    com/x/app/Application.java
    com/x/util/Alpha.java
    com/x/util/Beta.java

And packages are as you'd expect.

Initially, I could try a com/x/app/build.xml like:

    <project name="com.x.app.Application" default="compile" basedir="../..">
      <target name="compile">
        <javac srcdir="." destdir=".">
          <include name="com/x/app/*.java"/>
          <include name="com/x/util/*.java"/>
        </javac>
      </target>
    </project>

(Question: is this a reasonable build.xml?  Should it be in com/x/app,
or would you keep it somewhere else?  Would you use a different
project name, a different basedir, would you do the javac element
differently, etc.?)

One scaling problem is that I might not want to compile everything in
com/x/util - perhaps the still-being-developed DoesntWorkYet.java
doesn't compile.  I could change the javac element to:

        <javac srcdir="." destdir=".">
          <include name="com/x/app/Application.java">
          <include name="com/x/util/Alpha.java">
          <include name="com/x/util/Beta.java">
        </java>

but it's obvious that this direction of changes won't scale - suppose
com/x/util gets refactored to require com/x/util/NewStuff.java, etc.;
I don't want com/x/app to have to know the details of how com/x/util
is structured.

I could try using XML entities - after all, com/x/util is the best
place to keep the list of files I need to include - I might create
com/x/util/includes.xml:

    <include name="com/x/util/Alpha.java">
    <include name="com/x/util/Beta.java">
    
and change com/x/app/build.xml to:

    <?xml version="1.0"?>
    <!DOCTYPE project [
      <!ENTITY com.x.util.includes SYSTEM "file:../util/includes.xml">
    ]>
    <project name="com.x.app.Application" default="compile" basedir="../..">
      <target name="compile">
        <javac srcdir="." destdir=".">
          <include name="com/x/app/Application.java"/>
          &com.x.util.includes;
        </javac>
      </target>
    </project>

But com/x/util/includes.xml might itself use entities that
com/x/app/build.xml hasn't defined.  (XML's parameter entities might
provide a solution)

Or, stuff in com/x/util might be machine generated and thus might
impose dependancies on com/x/app's build.xml's compile target.

What's the Ant way of solving these kinds of problems?

tim

Re: Scaling to large projects

["M. Erik Husby" <mh...@genome.wi.mit.edu>]

The simplest way to scale to a large project is to organize your directories in a fashion 
similar to this:

project

   build.xml
   - src
      (all package sources)

   - classes
      (where all class files will end up.)

   - lib
       (where all third party jar files live)

   - deploy
       ( where you put the deployable files )


Then your build.xml can contain things like:
<path id="base.path">
  <pathelement location="./classes"/>
  <fileset dir="./lib">
   <include name="**/*.jar"/>
  </fileset>
</path>

<javac destdir="./classes">
       srcdir="./src">
 <classpath refid="base.path"/>
</javac>


Javac will compile everything under the source directory. You are free to add packages and refactor
classes as you see fit.

Erik Husby