Available Task

Available

Description

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.

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

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

  <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.