Nested properties in Ant

Today while scripting my Dopus Ant files I came across a problem with nested properties.

Something of the sort ${document.${input.file}.type}.

Turns out that Ant cannot do this by default. Yet I found a blog entry that explains how it can be done with newer versions of Ant (those that support macros). I adapted the solution a little bit with the following result:

<!-- Needed to resolve a nested property like ${document.${input.file}.type} -->
<macrodef name="resolveProperty">
<attribute name="property" />
<attribute name="value" />
<sequential>
<property name="tmp1.@{property}" value="document.@{value}.type" />
<resolveProperty2 property="@{property}" value="${tmp1.@{property}}" />
</sequential>
</macrodef>

<macrodef name="resolveProperty2">
<attribute name="property" />
<attribute name="value" />
<sequential>
<property name="@{property}" value="${@{value}}" />
</sequential>
</macrodef>

Now I can set my property like so:

<resolveProperty property="document.calculated.type" value="${project.input.file}" />

which effectively sets document.calculated.type=${document.${project.input.file}.type}.

Nice.