Ant Properties

Introduction#

Properties are key-value-pairs where Apache Ant tries to expand ${key} to value at runtime.

Ant properties are very helpful if you have to do a lot to processing to create installables or do custom deployments etc.

For example, you can mark ${src.dir} as source code directory,${lib.dir} as library for project,${javadoc.dir} for javadocs etc.

Instead of writing complete path at every location you can refer them by this place holder.

How to declare and use property in Ant.

Ant provides some built-in properties

In this example, We will create custom ant properties and use them to create a temporary directory and copy a file in it.

1. Properties declared within same file.

<project name="Test Project for Ant" default="init">
    <property name="temp.dir" value="${basedir}/temp" />

    <target name="init" description="initialize">
        <mkdir dir="${temp.dir}" />
        <copy file="${basedir}/test.xml" todir="${temp.dir}/" />
    </target>
</project>

In Ant, ${basedir} will refer to the base location or the location where your ant file is present. Here I declared a property named as

temp.dir

which will refer to basedir/temp location.

So, we call target init it will replace the placeholder ${temp.dir} with its actual value and start executing our script. This target will create a directory named temp under base directory copy test.xml file to temp directory.

2. Properties declared in different files.

In this example, We will refer properties declared in different file. This is a sample file(app_version.xml) which contains application version.

<project name="Project Properties">
     <property name="app.version" value="1.0" />
</project>

To include this file we will add the import ant task to import this file while executing ant targets.

<import file="app_version.xml" />

Above code will look like

<project name="Test Project for Ant" default="init">
<import file="app_version.xml" />
<property name="temp.dir" value="${basedir}/temp" />

<target name="init" description="initialize">
    <mkdir dir="${temp.dir}" />
    <copy file="${basedir}/test.xml" todir="${temp.dir}/" />
    <echo message="App version is:${app.version}" />
</target>

Once the file is imported, it can be directly accessed via property name(app.version).

I used .xml file, same use case will also work for .properties files.