Java Extreme Programming Cookbook

Regenerating Files That Have Changed

Problem

You want to control when files are regenerated.

Solution

Add the force attribute to any Ant Doclet task.

Discussion

Ant XDoclet tasks, by default, perform dependency-checking on generated files. These checks only regenerate files that are out of date with respect to their corresponding template files. There are times, though, that you may wish to force all generated files to be regenerated. For example, you may wish to do this if you are performing a clean build of the project from scratch, or you have upgraded to a newer version of XDoclet.

All XDoclet tasks, such as ejbdoclet, define an attribute called force. This attribute tells the XDoclet task whether to perform dependency-checking before generating a file. A value of “true” tells the XDoclet task to force generation of all files. A value other than “true” tells the XDoclet task to perform dependency-checking before generating a file. A dependency check simply looks at the timestamp of a source or template file and compares it with the timestamp of its generated files. If a source or template file has a timestamp that is greater than its generated files, then the files are regenerated. Example 9-1 shows how to add the force attribute to any XDoclet task.

Example 9-1. Using the force attribute to control dependency-checking

<target name="generate.ejb">
  <ejbdoclet
      ejbspec="2.0"
      destdir="${dir.generated.src}"      
      force="${force.generation}"> <!-- subtasks left out for brevity --> </ejbdoclet> ...