Using Ant to build J2EE Applications

Rajesh Kumar

www.scmGalaxy.com

Contents

  • Introduction
  • How does ANT work ?
  • Sample Build file
  • Built-in properties
  • ANT - Different flows
  • Writing your own task
  • Command-line options
  • IDE Integration
  • References

Introduction

What Is Ant?

  • A build tool like 'make'
  • Open source
    - from the Apache Jakarta project
    - http://ant.apache.org/
  • Implemented in Java
  • Used to build many open source products

Introduction ....Contd

  • Ease of use
    • - Ant is extended using Java classes
    - The configuration files are XML-based, calling out a target tree where various tasks get executed
    - Same config file (build.xml) can be across multiple platorms

How does ANT Work ?

  • Ant commands (or tasks) are implemented by Java classes
    • - many are built-in
    - others come in optional JAR files
    - custom commands can be created
  • Each project using Ant will have a build file
    • - typically called build.xml since Ant looks for this by default
  • Each build file is composed of targets
    • - these correspond to common activities like compiling and running code

Continued

  • Each target is composed of tasks
    • - Each task is run by an object that implements a particular Task interface
    - executed in sequence when the target is executed
    - like make, Ant targets can have dependencies
    - for example, modified source files must be compiled before the application can be run

How does ANT Work ? .. contd

  • Targets to be executed
    • - can be specified on the command line when invoking Ant
    - if none are specified then the default target is executed
    - execution stops if an error is encountered
    - so all requested targets may not be executed
  • Each target is only executed once
    • - regardless of the number of other targets that depend on it
    - for example
    • the "test" and "deploy" targets both depend on "compile"
    • the "all" target depends on "test" and "deploy" but "compile" is only executed once when "all" is executed

Continued

  • Some tasks are only executed when they need to be
    • - for example, files that have not changed since the last time they were compiled are not recompiled

Sample Build file


	<project name="test" default="hello">
    <target name="hello" depends="setup, pre-hello1, pre-hello2">
	<echo> Hello World</echo>
    </target>
    <target name="setup">
       <property name="company.name" value="MindTree"/>
       <condition property="os.is.solaris">
            <os name="SunOS" />
       </condition>
    </target>
   <target name="pre-hello1" if="os.is.solaris">
        <echo> You are running this script in Solaris </echo>
    </target>
    <target name="pre-hello2" unless="os.is.solaris">
        <echo> You are NOT running this script in Solaris </echo>
    </target>
</project>

Sample Build file

  • Save the file as test.xml in some temporary folder ( Say C:\Temp)
  • Set ANT_HOME= C:\Jakarta-Ant-1.5
  • Set PATH=%PATH%;%ANT_HOME%\bin
  • Cd C:\Temp
  • ant -buildfile test.xml
Buildfile: test.xml
	setup:
	pre-hello1:
	pre-hello2:
		[echo]  You are NOT running this script in Solaris
	hello:
		[echo]  Hello World
BUILD SUCCESSFUL
Total time: 1 second

Built-in Properties

  • Ant provides access to all system properties and also has some additional properties.
basedir The absolute path of the project's basedir (as set with the basedir attribute of <project>).
ant.file The absolute path of the buildfile.
ant.version The version of Ant
ant.project.name The name of the project that is currently executing; it is set in the name attribute of <project>.
ant.java.version the JVM version Ant detected;

Ant - Different flows

  • Using "depends"
  • Using "antcall"
  • Using "ant"

Ant - Different flows

  • Using "depends" - Last task to first task
    • Eg: 

						<target name="compile" depends="init, setup" description="compile the source " > 
	<!-- Compile the java code from ${src} into ${build} --> 
	<javac srcdir="${src}" destdir="${build}"/> 
</target>

Ant - Different flows

  • Using "antcall" -- Sequential & Functional oriented
    • Calling different targets in the same build.xml (very similar to calling functions in regular programming language)
    Eg: 

					
						<antcall target="copymodule">
      <param name="module.name" value="user"/>
 </antcall>
 <target name="copymodule" if="gws.prepared">
        <echo>Module : ${module.name} </echo>
        <copy todir="${gws.app}/j2ee-apps/gws/${module.name}" 	
						includeEmptyDirs="no">
            <fileset dir="${gws.class.folder}">
                <patternset>
                    <include name="**/${module.name}/**"/>
                </patternset>
            </fileset>
        </copy>
</target>

Ant - Different flows

  • Using "ant"
    • This is used for running scripts for sub-projects
    Eg: 

	<target name="ROOT">
    <ant dir="${basedir}/ROOT" target="dist"/>
  </target>
  <target name="examples">
    <ant dir="${basedir}/examples" target="dist"/>
	   <ant antfile="subproject/subbuild.xml" dir="${basedir}/subproject" target="compile"/> 
  </target>

Core & Optional tasks

http://ant.apache.org/manual/index.html

Writing your own task

  1. Create a Java class that extends org.apache.tools.ant.Task
  2. For each attribute, write a setter method.
  3. Implement the interface org.apache.tools.ant. TaskContainer if your task contains other tasks as nested elements
  4. Write a public void execute method, with no arguments, that throws a BuildException
  5. Adding your task to the system
    1. Make sure the class that implements your task is in the classpath when starting Ant.
    2. Add a <taskdef> element to your project. This actually adds your task to the system.
    3. Use your task in the rest of the buildfile.
6. Eg: 

					<?xml version="1.0"?> 
	<project name="OwnTaskExample" default="main" basedir="."> 	
	    <taskdef name="mytask" classname="com.mydomain.MyVeryOwnTask"/> 
		<target name="main"> 
			<mytask message="Hello World! MyVeryOwnTask works!"/> 
		</target> 
	</project

Command line options

ant [options] [target [target2 [target3] ...]]

Options:
-help print this message
-projecthelp print project help information
-version print the version information and exit
-diagnostics print information that might be helpful to diagnose or report problems.
-quiet, -q be extra quiet
-verbose, -v be extra verbose

Command line options Contd...

-debug print debugging information
-emacs produce logging information without adornments
-logfile <file> use given file for log
-l <file> ""
-logger <classname> the class which is to perform logging
-listener <classname> add an instance of class as a project listener
-buildfile <file> use given buildfile

Command line options Contd...

-file <file> ""
-f <file> ""
-D<property>=<value> use value for given property
-propertyfile taking precedence
-inputhandler <class> the class which will handle input requests
-find <file> <name> load all properties from file with -D properties search for buildfile towards the root of the filesystem and use it

IDE Integration

References

More References

Thank You!

www.scmGalaxy.com