ANT script good practices – few thoughts

In general scripts should be treated as first class citizens, so they need to be simple, modular, clean, easy to read and understand and loosely coupled.

Here are some techniques which should help with it:

All the OO principles apply!

When you need custom functionality for your project i.e. custom make step – do not bloat the common files with conditional logic. Extract common stuff to macrodefs and create separate files and/or targets for custom functionality in local project directory. Basically all the OO principles apply!

Break it down and modularize

You wouldn’t like to have just one big class in your project – do the same with ant script, break it down and modularize

Stop writing generic ant targets parametrized by global properties

Replace them with macrodefs. See:
http://ant.apache.org/manual/CoreTasks/macrodef.html

Stop using global properties

Don’t use them, unless they are really global i.e. project.name, project.version. In general they are evil as global variables and singletons are. See:
http://blogs.msdn.com/scottdensmore/archive/2004/05/25/140827.aspx
http://www.cs.usfca.edu/~wolber/courses/110/lectures/globals.htm

Use convention over configuration design paradigm.

What does it mean? Basically this:
Instead of writing (unneccessary abstraction and complexity):

<property name="project.dir" value="${basedir}"/>
<property name="test.result.dir" value="${project.dir}/build/testresult"/>
<javadoc dest="${test.result.dir}>
...


We would write:

<javadoc dest="build/testresult">
...

Simpler and more readable!
See more here:
http://en.wikipedia.org/wiki/Convention_over_Configuration

Use maven-like project directory structure

This supports convention over configuration approach and simplifies your build scripts.

project
- src
  +- main
     +- java
     +- config
     +- scripts
     +- ...
  +- test
     +- java
     +- config
     +- ...
- lib
  +- compile
  +- runtime
     +- spring-2.0.jar
     +- jakarta-commons
        +- commons-io.jar
        +- commons-???.jar
     +- ...
  +- test
- ant (contains common ant tasks - it should be symbolic link as this scripts should be shared)
  +- ant-common.xml
  +- ant-test.xml
  +- ...
- target ( temporary directory, only RW area of the project, equivalent to build)
- modules (if the code contains modules build separately like c++)
  +- SomeNativeLib
      +- src
      +- lib
      +- ...
  +- OtherJavaModule
      +- src
      +- lib
      +- ...
- build.xml

Enjoy!