Sets a property if a resource is available at runtime. This resource can be a file, a directory, a class in the classpath, or a JVM system resource.
If the resource is present, the property value is set to true by
default; otherwise, the property is not set. You can set the value to
something other than the default by specifying the value attribute.
Normally, this task is used to set properties that are useful to avoid target execution depending on system parameters.
| Attribute | Description | Required |
| property | The name of the property to set. | Yes |
| value | The value to set the property to. Defaults to "true". | No |
| classname | The class to look for in the classpath. | Yes |
| file | The file to look for. | |
| resource | The resource to look for in the JVM. | |
| classpath | The classpath to use when looking up classname or resource. |
No |
| filepath | The path to use when looking up file. |
No |
| classpathref | The classpath to use, given as a reference to a path defined elsewhere. | No |
| type | The type of file to look for, either a directory (type="dir") or a file
(type="file"). If not set, the property will be set if the name specified in the file
attribute exists as either a file or a directory. |
No |
| ignoresystemclasses | Ignore Ant's runtime classes, using only the specified classpath. Only affects the "classname" attribute. Defaults to "false" | No |
| searchparents | This contains the behaviour of the "file" type. If true, the available task will, when searching for a file, search not only the directories specified but will also search the parent directories of those specified. If false, only the directories specified will be searched. Defaults to "false". Since Ant 1.7 | No |
Available's classpath attribute is a path-like structure and can also be set via a nested
<classpath> element.
Available's filepath attribute is a path-like structure and can also be set via a nested
<filepath> element.
<available classname="org.whatever.Myclass" property="Myclass.present"/>
sets the Myclass.present property to the value "true"
if the class org.whatever.Myclass is found in Ant's classpath.
<property name="jaxp.jar" value="./lib/jaxp11/jaxp.jar"/>
<available file="${jaxp.jar}" property="jaxp.jar.present"/>
sets the jaxp.jar.present property to the value "true"
if the file ./lib/jaxp11/jaxp.jar is found.
<available file="/usr/local/lib" type="dir"
property="local.lib.present"/>
sets the local.lib.present property to the value "true"
if the directory /usr/local/lib is found.
...in project ...
<property name="jaxp.jar" value="./lib/jaxp11/jaxp.jar"/>
<path id="jaxp" location="${jaxp.jar}"/>
...in target ...
<available classname="javax.xml.transform.Transformer"
classpathref="jaxp" property="jaxp11.present"/>
sets the jaxp11.present property to the value "true"
if the class javax.xml.transform.Transformer is found in the classpath referenced by jaxp (in this case, ./lib/jaxp11/jaxp.jar).
<available property="have.extras" resource="extratasks.properties">
<classpath>
<pathelement location="/usr/local/ant/extra.jar" />
</classpath>
</available>
sets the have.extras property to the value "true"
if the resource-file extratasks.properties is found.