Eureka!

Ant Tasks, such as <if>, belongs to ant-contrib.jar. So in order to use them in maven-antrun-plugin, you have to add this dependency explicitly in the pom.xml.

<!-- Properties -->
<properties>
	<greeting>true</greeting>
</properties>

<!-- Build Configuration -->
<build>
	<plugins>
		<plugin>
			<artifactId>maven-antrun-plugin</artifactId>
			<version>1.3</version>
			<dependencies>
				<dependency>
					<groupId>ant-contrib</groupId>
					<artifactId>ant-contrib</artifactId>
					<version>20020829</version>
				</dependency>
			</dependencies>
			<executions>
				<execution>
					<id>initialize</id>
					<phase>initialize</phase>
					<configuration>
						<tasks>
							<!-- add the ant tasks from ant-contrib -->
							<taskdef resource="net/sf/antcontrib/antcontrib.properties" />

							<!-- show greeting if ${greeting} is set to true-->
							<if>
								<equals arg1="${greeting}" arg2="true" />
								<then>
									<echo>Hello World</echo>
								</then>
							</if>
						</tasks>
					</configuration>
					<goals>
						<goal>run</goal>
					</goals>
				</execution>
			</executions>
		</plugin>
	</plugins>
</build>

Please remember to add the tasks definition of ant-contrib.jar using the <taskdef> inside the <tasks> node.

Run mvn initialize, the console will echo the greeting message only if the ${greeting} property is set to true.

Done =)

maven-antrun-plugin allows maven user to add ant tasks in different maven life cycle phases. To use the maven-antrun-plugin, add the following text in the pom.xml.

<!-- Build Configuration -->
<build>
	<plugins>
		<plugin>
			<artifactId>maven-antrun-plugin</artifactId>
			<executions>
				<execution>
					<id>initialize</id>
					<phase>initialize</phase>
					<configuration>
						<tasks>
							<echo>Hello Maven</echo>
						</tasks>
					</configuration>
					<goals>
						<goal>run</goal>
					</goals>
				</execution>
			</executions>
		<plugin>
	</plugins>
</build>

This is the output after running mvn initialize

...
[INFO] task-segment: [initialize]
[INFO] ------------------------------------------------------------------------
[INFO] [antrun:run]
[INFO] Executing tasks
     [echo] Hello Maven
[INFO] Executed tasks
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: < 1 second
[INFO] Finished at: Wed Dec 16 18:04:57 CST 2009
[INFO] Final Memory: 2M/7M
[INFO] ------------------------------------------------------------------------

Done =)