How to generate build.xml file

This example shows how to generate the build.xml file. You may say that build.xml file is the backbone of ANT (Another Neat Tool) technology. Each build.xml file contains only one project name and at least one target. The project tag has only three attributes:

Project

Attribute	Description	Requirement
name	project name	not necessary
default	target name which called by default	not necessary
basedir	the base directory having all path, it contain absolute path	not necessary

<project name="My Project" default="compile" basedir=".">


The project tag is used to create our project and its attributes are used to handle further processing of the project. The name attribute is used to specify the project name and the default attribute is used to specify which target will be called as default when the program will run and the basedir attribute is used to calculate the absolute path of the parent directory. 

An another tag is Target tag which has following five attributes:

Target

Attribute	Description	Requirement
name	target name	necessary
depends	depends on another target	not necessary
if	the name of the property that must be set in order for this target to execute.	not necessary
unless	the name of the property that must not be set in order for this target to execute.	not necessary
description	short description about target	not necessary

<target name="buildWar" depends="init" description="build a war file"/>

<target name="init" if="build"/>
<target name="init" unless="build"/>



In the target tag, name attribute is used for target name and the depends attribute is used to give sequence of target, i.e., which target will execute first, one target may depend on one or more other targets. The if attribute is used in case of condition, whether property exists or not; then this target will be executed and unless attribute is used as like else condition whether property does not exist, the target will not be executed and the description attribute is used for only giving details about target.

Next tag is property tag which has following four attribute:

Property

Attribute	Description	Requirement
name	name of the property, which is case-sensitive	not necessary
value	name of task attribute, this is done by placing the property name between "${"name }" in the attribute value	necessary
location	it contain property name	not necessary
file	name of the property file	not necessary

<property name="build" value="${build}"/> 

<property name="src" location="src"/> 

<property file="build.properties"/>

In the property tag, name attribute is used for property name; it is case sensitive. The value tag is used to give the task which will be the name of property in this format "${name}", and the location tag is used to specify the location of task where it performs and the file tag is used to import all properties of ant file. The complete build.xml file structure is as follows:

<project name="My Project" default="jar" basedir=".">

<property name="dir.src" value="src"/>
<property name="dir.build" value="build"/>
<property name="dir.dest" value="dest"/>

<target name="clean" description="Removing the all generated files.">
<delete dir="${dir.build}"/>
<delete dir="${dir.dest}"/>
</target>

<target name="prepare" depends="clean">
<mkdir dir="${dir.build}"/>
<mkdir dir="${dir.dest}"/>
<mkdir dir="${dir.src}"/>
</target>

<target name="compile" depends="prepare" description="Compilation of all source code.">
<javac srcdir="${dir.src}" destdir="${dir.build}"/>
</target>

<target name="jar" depends="compile" description="Generates news.jar file in to the 'dest' directory.">
<jar jarfile="${dir.dest}/news.jar" basedir="${dir.build}"/>
</target>

</project>

The above build.xml file is used to create directory, compile source code, create jar file and clean the directory if already exists. To check the program, simply copy and paste the above code and give appropriate path; then run with ant command on the command prompt. 

The output shows that a jar file named news.jar is created but in this jar file only manifest file is created. When you make a java file in the src folder and run with ant command, the jar file is created completely.

class Hello
{
  public static void main(String args[]){
  System.out.println("muraliraj");
  }
}

To check your program, compile it with ant command on the console; 


then the following output will be displayed:  Build Successful