How can I iterate over properties from a file?

Question

All my projects and their versions are defined in a properties file like this:

ProjectNameA=0.0.1
ProjectNameB=1.4.2

I'd like to iterate over all the projects, and use their names and versions in an Ant script.

At present I read the entire file using the property task, then iterate over a given list in a for loop like this:

<for list="ProjectNameA,ProjectNameB" param="project">
   <sequential>
    <echo message="@{project} has version ${@{project}}" />
   </sequential>
</for>

How can I avoid the hard-coding of the project names in the for loop? Basically iterate over each line and extract the name and the version of a project as I go.

Kerrin

Answer 1

Seeing as you're already using antcontrib for, how about making use of the propertyselector task:

<property file="properties.txt" prefix="projects."/>
<propertyselector property="projects" match="projects\.(.*)" select="\1"/>

<property file="properties.txt" />
<for list="${projects}" param="project">
    ...
</for>

The idea here is to read the properties once with the projects prefix, and use the resulting set of properties to build a comma-separated list of projects with the propertyselector task. Then the properties are re-read without the prefix, so that your for loop can proceed as before.

Bluebeard

Added relation to a given bug, and the sequential alement to the for element to make it more obvious. – Whitnell

Wanted to add an edit, but it was rejected. So I add it as a comment: the for task is not listed somehow in the antcontrib.properties in the latest jar. A workaround is to include it as an class with a name in a taskdef like it is stated in the bug report at sourceforge.net/tracker/… – Whitnell

Thanks for the post Martin. For others who did not have things setup for ant contrib, you may need the following line too: <taskdef resource="net/sf/antcontrib/antlib.xml"/> Reference: ant-contrib.sourceforge.net/tasks/index.html#intro – Liripipe

Answer 2

Something you want to keep in mind, if you are reading additional .property files (besides build.properties) is scoping. If you read an additional file (via the property file="foo.property") tag, ant will show that the file was read, and the properties loaded. However, when you goto reference them, they come up un-defined.

Beside