Exits the current build (just throwing a BuildException), optionally printing additional information.
The message of the Exception can be set via the message attribute or character data nested into the element.
| 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 |
As 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
<fail/>
will exit the current build with no further information given.
BUILD FAILED build.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 FAILED build.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 FAILED build.xml:2: unless=thisdoesnotexistUsing a condition to achieve the same effect:
<fail>
<condition>
<not>
<isset property="thisdoesnotexist"/>
</not>
</condition>
</fail>
Output:
BUILD FAILED build.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 build will fail.