taskdef example

gistfile1.xml

<taskdef name="echoFail" >
	<stringparams>
		<stringparam name="task" />
		<stringparam name="message" required="false" />
	</stringparams>

	<do>
		<property name="customMessage" value="__message__" />
		<if test="${customMessage == ''}" >
			<property name="customMessage" value="this is a default message" />
		</if>
		<__task__ message="${customMessage}" />
	</do>
</taskdef>
...
<!-- echos the default message -->
<echoFail task="echo" />
...
<echoFail task="fail" message="this will fail the build" />