Available Task

Available

Description

Sets a property if a resource is available at run time. This resource can be a file, a directory, a class in the classpath, or a JVM system resource.

Note: a class is available in the classpath when it can be loaded; i.e., all classes it depends on must be in the classpath, too.

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.

Parameters

Attribute	Description	Required
property	The name of the property to set.	Yes
value	The value to set the property to.	No; defaults to true
classname	The class to look for in the classpath.	Exactly one of the three
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.	No; defaults to false
searchparents	This contains the behaviour of the file `type`. If true, the 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. Since Ant 1.7	No; defaults to false

Parameters specified as nested elements

classpath

Available's classpath attribute is a path-like structure and can also be set via a nested <classpath> element.

filepath

Available's filepath attribute is a path-like structure and can also be set via a nested <filepath> element.

Examples

Set the Myclass.present property to the value true if the class org.whatever.Myclass is found in Ant's classpath.

<available classname="org.whatever.Myclass" property="Myclass.present"/>

Set the jaxp.jar.present property to the value true if the file ./lib/jaxp11/jaxp.jar is found.

<property name="jaxp.jar" value="./lib/jaxp11/jaxp.jar"/>
<available file="${jaxp.jar}" property="jaxp.jar.present"/>

Set the local.lib.present property to the value true if the directory /usr/local/lib is found.

<available file="/usr/local/lib" type="dir"
           property="local.lib.present"/>

Set 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).

...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"/>

Set the have.extras property to the value true if the resource file extratasks.properties is found.

<available property="have.extras" resource="extratasks.properties">
  <classpath>
    <pathelement location="/usr/local/ant/extra.jar"/>
  </classpath>
</available>