Script Task

## Script

### Description

Execute a script in a Apache BSF or JSR 223 supported language.

Note: This task depends on external libraries not included in the Ant distribution. See Library Dependencies for more information.

The task may use the BSF scripting manager or the JSR 223 manager that is included in JDK6 and higher. This is controlled by the `manager` attribute. The JSR 223 scripting manager is indicated by "javax".

All items (tasks, targets, etc) of the running project are accessible from the script, using either their `name` or `id` attributes (as long as their names are considered valid Java identifiers, that is). This is controlled by the "setbeans" attribute of the task. The name "project" is a pre-defined reference to the Project, which can be used instead of the project name. The name "self" is a pre-defined reference to the actual `<script>`-Task instance.
From these objects you have access to the Ant Java API, see the JavaDoc (especially for Project and Script) for more information.

If you are using JavaScript a good resource is http://www.mozilla.org/rhino/doc.html as we are using their JavaScript interpreter.

Scripts can do almost anything a task written in Java could do.

Rhino provides a special construct - the JavaAdapter. With that you can create an object which implements several interfaces, extends classes and for which you can overwrite methods. Because this is an undocumented feature (yet), here is the link to an explanation: Groups@Google: "Rhino, enum.js, JavaAdapter?" by Norris Boyd in the newsgroup netscape.public.mozilla.jseng.

### Parameters

Attribute | Description | Required
language | The programming language the script is written in. Must be a supported Apache BSF or JSR 223 language | Yes
manager | Since: Ant 1.7. The script engine manager to use. This can have one of three values ("auto", "bsf" or "javax"). The default value is "auto". "bsf" use the BSF scripting manager to run the language. "javax" use the javax.scripting manager to run the language. (This will only work for JDK6 and higher). "auto" use the BSF engine if it exists, otherwise use the javax.scripting manager. | No
src | The location of the script as a file, if not inline | No
setbeans | This attribute controls whether to set variables for all properties, references and targets in the running script. If this attribute is false, only the the "project" and "self" variables are set. If this attribute is true all the variables are set. The default value of this attribute is "true". Since Ant 1.7 | No
classpath | The classpath to pass into the script. Since Ant 1.7 | No
classpathref | The classpath to use, given as a reference to a path defined elsewhere. Since Ant 1.7 | No

### Parameters specified as nested elements

#### classpath

Since Ant 1.7

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

If a classpath is set, it will be used as the current thread context classloader, and as the classloader given to the BSF manager. This means that it can be used to specify the classpath containing the language implementation for BSF or for JSR 223 managers. This can be usefull if one wants to keep /Users/antoine/.ant/lib free of lots of scripting language specific jar files.

NB: This classpath cannot (currently) be used to specify the location of the BSF jar file. Also, due to classloading issues, languages that have engines in the BSF jar file cannot have the implementation in the classpath element. This includes the javascript, jython, netrexx and jacl languages.

### Examples

The following snippet shows use of five different languages:

>         <property name="message" value="Hello world"/>

>         <script language="groovy">
>           println("message is " + message)
>         </script>

>         <script language="beanshell">
>           System.out.println("message is " + message);
>         </script>

>         <script language="judoscript">
>             println 'message is ', message
>         </script>

>         <script language="ruby">
>             print 'message is ', $message, "\n"
>         </script>

>         <script language="jython">
>     print "message is %s" % message
>         </script>

Note that for the jython example, the script contents must start on the first column.

Note also that for the ruby example, the names of the set variables are prefixed by a '$'.

The following script shows a little more complicated jruby example:

>     <script language="ruby">
>       xmlfiles = Dir.new(".").entries.delete_if { |i| ! (i =~ /\.xml$/) }
>       xmlfiles.sort.each { |i| $self.log(i) }
>     </script>

The same example in groovy is:

>     <script language="groovy">
>       xmlfiles = new java.io.File(".").listFiles().findAll{ it =~ "\.xml$"}
>       xmlfiles.sort().each { self.log(it.toString())}
>     </script>

The following example shows the use of classpath to specify the location of the beanshell jar file.

>     <script language="beanshell" setbeans="true">
>       <classpath>
>         <fileset dir="/Users/antoine/lang/beanshell" includes="*.jar" />
>       </classpath>
>       System.out.println("Hello world");
>     </script>

The following script uses javascript to create a number of echo tasks and execute them.

>     <project name="squares" default="main" basedir=".">

>       <target name="main">

>         <script language="javascript"> <![CDATA[

>           for (i=1; i<=10; i++) {
>             echo = squares.createTask("echo");
>             echo.setMessage(i*i);
>             echo.perform();
>           }

>         ]]> </script>

>       </target>

>     </project>

generates

>     main:
>     1
>     4
>     9
>     16
>     25
>     36
>     49
>     64
>     81
>     100

>     BUILD SUCCESSFUL

Now a more complex example using the Java API and the Ant API. The goal is to list the filesizes of all files a `<fileset/>` caught.

>     <?xml version="1.0" encoding="ISO-8859-1"?>
>     <project name="MyProject" basedir="." default="main">

>       <property name="fs.dir" value="src"/>
>       <property name="fs.includes" value="**/*.txt"/>
>       <property name="fs.excludes" value="**/*.tmp"/>

>       <target name="main">
>         <script language="javascript"> <![CDATA[

>           // import statements
>           // importPackage(java.io);
>           importClass(java.io.File);

>           // Access to Ant-Properties by their names
>           dir      = project.getProperty("fs.dir");
>           includes = MyProject.getProperty("fs.includes");
>           excludes = self.getProject()  .getProperty("fs.excludes");

>           // Create a <fileset dir="" includes=""/>
>           fs = project.createDataType("fileset");
>           fs.setDir( new File(dir) );
>           fs.setIncludes(includes);
>           fs.setExcludes(excludes);

>           // Get the files (array) of that fileset
>           ds = fs.getDirectoryScanner(project);
>           srcFiles = ds.getIncludedFiles();

>           // iterate over that array
>           for (i=0; i<srcFiles.length; i++) {

>             // get the values via Java API
>             var basedir  = fs.getDir(project);
>             var filename = srcFiles[i];
>             var file = new File(basedir, filename);
>             var size = file.length();

>             // create and use a Task via Ant API
>             echo = MyProject.createTask("echo");
>             echo.setMessage(filename + ": " + size + " byte");
>             echo.perform();
>           }
>         ]]></script>
>       </target>
>     </project>

We want to use the Java API. Because we don't want always typing the package signature we do an import. Rhino knows two different methods for import statements: one for packages and one for a single class. By default only the java packages are available, so java.lang.System can be directly imported with `importClass/importPackage`. For other packages you have to prefix the full classified name with Packages. For example Ant's FileUtils class can be imported with `importClass(Packages.org.apache.tools.ant.util.FileUtils)`
The `<script>` task populates the Project instance under the name project, so we can use that reference. Another way is to use its given name or getting its reference from the task itself.
The Project provides methods for accessing and setting properties, creating DataTypes and Tasks and much more.
After creating a FileSet object we initialize that by calling its set-methods. Then we can use that object like a normal Ant task (`<copy>` for example).
For getting the size of a file we instantiate a `java.io.File`. So we are using normal Java API here.
Finally we use the `<echo>` task for producing the output. The task is not executed by its execute() method, because the perform() method (implemented in Task itself) does the appropriate logging before and after invoking execute().