Objectives

Ant is a Java tool that automates various tasks typically associated with the development, compilation, distribution, installation and cleaning.

Ant does what is dictated by a construction file (build file), written in XML format. By default, the file is called "build.xml".

Build.xml example:

<project name="MyProject" default="compile" basedir=".">

    <description> simple example build file </ description>

    <property name="src.dir" location="src"/>
    <property name="build.dir" location="build"/>

    <target name="init">
        <mkdir dir="${build.dir}"/>
    </ Target>

    <target name="compile" depends="init" description="Compiles the source code">
        <javac srcdir="${src.dir}" destdir="${build.dir}"/>
    </ Target>

    <target name="show" description="Shows property values">
        <echo message="src.dir = ${src.dir}" />
        <echo message="build.dir = ${build.dir}" />
    </ Target>

</ Project>

These are the targets you may call:

• ant init - creates temporary directories
• ant compile - depends on init, and compiles the program code
• ant show - shows the value of properties

Project, target, task, and property

A project (project) defines several targets (targets) that perform tasks (tasks), parameterized by properties (properties).

A target (target) defines a set of tasks to be performed. The field 'depends' indicates the targets that must be executed before the current one. Each target is only executed once.

Dependencies of a target:

<target name="A"/>
<target name="B" depends="A"/>
<target name="C" depends="B"/>
<target name="D" depends="C,B,A"/>

...


> ant D

A task (task) is a procedure that can be run within a target. Each one has several specific attributes that act as arguments for its implementation. Some examples of basic tasks are included in the Ant: javac, java, mkdir, copy, replace, tstamp. There is also the possibility to extend Ant with new tasks.

A property (property) is a pair name value. When you refer ${name} in text, it is replaced by a value. For example, if the property 'dir' has the value 'c :/ proj', then '${dir}/classes' is replaced by 'c:/proj/classes'.

The properties can be defined in file construction, read from a file or set on the command line:

<property name="dir" value="c:/proj" />

...

<property file="build.properties" />

...

> Ant-DNAME = value target

The value of a property can be set only once. After that, the value can only be changed temporarily.

Typical directory structure

A directory structure typically associated with an Ant project looks as follows:

src
config
lib
build
dist

1. In src is the source code (Java files).
2. In config are configuration files (.properties, among others).
3. In lib are extra libraries (.jar).
4. The build directory is temporary and serves to save the compiled classes of the program (.class) and other auxiliary files.
5. The dist directory is temporary and serves to keep the final results of the compilation, for example, a JAR file.

Example

Example file full of construction:

<project name="MyProject" default="run" basedir=".">

    <description> simple example build file </ description>

    <property name="src.dir" location="src"/>
    <property name="build.dir" location="build"/>

    <property name="run.mainclass" value="pacote.Programa"/>
    <property name="run.args" value="etc\input_file.txt etc\output_file.txt"/>

    <target name="init">
        <mkdir dir="${build.dir}"/>
    </ Target>

    <target name="clean" description="Delete the build directory">
        <delete dir="${build.dir}"/>
    </ Target>

    <target name="compile" depends="init" description="Compiles the source code">
        <javac srcdir="${src.dir}" destdir="${build.dir}"/>
    </ Target>

    <target name="run" depends="compile" description="Runs the program">
        <java classname="${run.mainclass}" fork="true">
            <arg line="${run.args}" />
            <classpath>
                <pathelement location="${build.dir}"/>
            </ Classpath>
        </ Java>
    </ Target>

    <target name="show" description="Shows property values">
        <echo message="src.dir = ${src.dir}" />
        <echo message="build.dir = ${build.dir}" />
        <echo message="run.mainclass = ${run.mainclass}" />
        <echo message="run.args = ${run.args}" />
    </ Target>

</ Project>

• ant init - creates temporary directories
• ant clean - cleans temporary directories
• ant compile - depends on init, and compiles the program code
• ant run - depends on compile, which depends on init and runs the compiled program
• prev show - shows the value of property used and can be parameterized
• ant-foo = Drun.args show - modifies the value of a property on the command line