The assertions type enables or disables the Java 1.4 assertions feature,
on a whole Java program, or components of a program. It can be used
<junit> to add extra validation to code.
Assertions are covered in the Java SE documentation, and the Java Language Specification.
The key points to note are that a java.lang.AssertionError is thrown when an assertion fails, and that the facility is only available on Java 1.4 and later. To enable assertions one must set source="1.4" (or later) in <javac> when the source is being compiled, and that the code must contain assert statements to be tested. The result of such an action is code that neither compiles or runs on earlier versions of Java. For this reason Apache Ant itself currently contains no assertions.
When assertions are enabled (or disabled) in a task through nested assertions elements, the class loader or command line is modified with the appropriate options. This means that the JVM executed must be a Java 1.4 or later JVM, even if there are no assertions in the code. Attempting to enable assertions on earlier VMs will result in an "Unrecognized option" error and the JVM will not start.
|enableSystemAssertions||Flag to turn system assertions on or off.||No; default is "unspecified"|
When system assertions have been neither enabled nor disabled, then the JVM is not given any assertion information - the default action of the current JVMs is to disable system assertions.
Note also that there is no apparent documentation for what parts of the JRE come with useful assertions.
Enable assertions in portions of code. If neither a package nor class is specified, assertions are turned on in all (user) code.
|class||The name of a class on which to enable assertions.||No|
|package||The name of a package in which to enable assertions on all classes. (Includes subpackages.) Use "..." for the anonymous package.||No|
Disable assertions in portions of code.
|class||The name of a class on which to disable assertions.||No|
|package||The name of a package in which to disable assertions on all classes. (Includes subpackages.) Use "..." for the anonymous package.||No|
Because assertions are disabled by default, it only makes sense to disable assertions where they have been enabled in a parent package.
<assertions> <enable/> </assertions>
<assertions> <enable class="Test"/> </assertions>
<assertions> <enable package="org.apache"/> </assertions>
<assertions enableSystemAssertions="true"> <enable package="org.apache"/> <disable package="org.apache.tools.ant"/> <enable class="org.apache.tools.ant.Main"/> </assertions>
<assertions enableSystemAssertions="false"> <enable package="..."/> </assertions>
<assertions id="project.assertions"> <enable package="org.apache.test"/> </assertions> <assertions refid="project.assertions"/>