Thu, 09. Oct 2003
Customization and User Preferences with <presetdef>

This is another new kid on the Ant 1.6 block. <presetdef> will let you define your own default values for attributes and even for nested elements.

If you've always thought that <ant>'s inheritall attribute should be false by default, you are not only correct (but there is this backwards compatibility issue) but can now use 

  <presetdef name="better-ant">
    <ant inheritall="false"/>
  </presetdef>
and then use <better-ant> the same way you used <ant>. You can even set inheritall to true in your better-ant invocation if you want to.

The example from the manual uses <javac>: 

  <presetdef name="my.javac">
     <javac debug="${debug}" deprecation="${deprecation}">
        <src path="${gen.dir}"/>
     </javac>
  </presetdef>
this shows two things:
  1. the debug and deprecation attributes take their default values from properties. If you use <my.javac> instead of <javac> throughout your build file, you can be sure that running ant -Ddebug=on will apply to all compilation tasks. No need to remember to put the customization into each task.
  2. The path ${gen.dir} will be added to <javac>s source path automagically.

While you may be able to override attributes set via <presetdef> when you use the task, you can not suppress child elements.

path: /en/Apache/Ant | #