Apache Ant TasksFailFailDescriptionExits the current build (just throwing a BuildException), optionally printing additional information. The message of the Exception can be set via the message attributeor character data nested into the element. Parameters | Attribute | Description | Required | | message | A message giving further information on why the build exited | No | | if | Only fail if a property of the given name exists in the current project | No | | unless | Only fail if a property of the given name doesn't exist in the current project | No | | status | Exit using the specified status code; assuming the generated Exception is not caught, the JVM will exit with this status. Since Apache Ant 1.6.2 | No | Parameters specified as nested elementsAs an alternative to the if/unless attributes, conditional failure can be achieved using a single nested <condition> element, which should contain exactly one core or custom condition. For information about conditions, see here.
Since Ant 1.6.2 Examples <fail/> will exit the current build with no further information given. BUILD FAILEDbuild.xml:4: No message <fail message="Something wrong here."/> will exit the current build and print something like the following to wherever your output goes: BUILD FAILEDbuild.xml:4: Something wrong here. <fail>Something wrong here.</fail> will give the same result as above. <fail unless="thisdoesnotexist"/> will exit the current build and print something like the following to wherever your output goes: BUILD FAILEDbuild.xml:2: unless=thisdoesnotexist Using a condition to achieve the same effect: <fail> <condition> <not> <isset property="thisdoesnotexist"/> </not> </condition> </fail> Output: BUILD FAILEDbuild.xml:2: condition satisfied <fail message="Files are missing."> <condition> <not> <resourcecount count="2"> <fileset id="fs" dir="." includes="one.txt,two.txt"/> </resourcecount> </not> </condition></fail> Will check that both files one.txt and two.txt are present otherwise the buildwill fail. | 
