Using JavaScript in Ant

Question

I am having issues using the <script> tag in Ant and I am hoping someone can help. I want to use JavaScript in my Ant build.xml. Something like the following:

<?xml version="1.0" encoding="UTF-8"?>
<project name="java" default="main" basedir=".">
  <target name="main">
    <script language="javascript"> <![CDATA[
 println("hello, world")
    ]]> </script>
  </target>
</project>*

Unfortunately this only displays and error:

build.xml:4: Could not create task or type of type: script.

I have located the required jar file (js.jar) for this to work and moved it to ANT_HOME/lib, but I am still stuck as of how to get this to work.

Which version of Ant are you using? Run "ant -version" on the command line. Also, which OS are you running? — Chad Nouis
– Chad Nouis, Commented Apr 16, 2013 at 15:53
What is your java version ? See my comment on the answer of Chad — Rebse
– Rebse, Commented Apr 18, 2013 at 19:20
also 2 problems => missing ';' after println.. and trailing '*' after closing project tag — Rebse
– Rebse, Commented Apr 18, 2013 at 19:34

Chad Nouis · Accepted Answer · 2013-04-18 15:57:47Z

3

In addition to js.jar, you need to add bsf.jar and commons-logging-*.jar to ANT_HOME/lib. In your Ant distribution, there is a file named docs/manual/install.html. The Library Dependencies section of this HTML file documents where you can download these files.

println isn't supported in JavaScript. Instead, use the following:

<project name="jsTest" default="main">
  <target name="main">
    <script language="javascript"> <![CDATA[
        var echo = jsTest.createTask("echo");
        echo.setMessage("hello, world");
        echo.perform();
    ]]> </script>
  </target>
</project>

answered Apr 18, 2013 at 15:57

Chad Nouis

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4 Comments

Rebse Over a year ago

you don't need js.jar and bsf.jar anymore, as jdk >= 6 ships with a builtin Javascript Scripting Engine based on Rhino 1.6R2

Rebse Over a year ago

why not simply use print("hello, world"); instead ?

Chad Nouis Over a year ago

Ant 1.6.5 doesn't work with JDK 1.6's JavaScript engine. If user2286073 upgrades to Ant 1.7 or later, then all of these issues will be resolved.

Rebse Over a year ago

you're are right, using ant 165 will produce java.lang.NoClassDefFoundError: org/apache/bsf/BSFException

Dmitriy Pichugin · Accepted Answer · 2017-07-13 05:35:53Z

3

You can also instantiate and use Java classes in Javascript as available via Rhino(JRE pre 1.8) or Nashorn(JRE 1.8+) when you need to.

<script language="javascript">
  with(new JavaImporter(java.lang, java.io)){
    System.out.println("hello, world");// <--!!!
  }
</script>

You may create and use JavaScript functions of your own.

<script language="javascript">
  with(new JavaImporter(java.lang, java.io)){
    var fun = function(a,b){
      System.out.println(a+b);
    };
    fun(1,2);
  }
</script>

Code above prints

3.0

Loops, recursion and everything you've been dreaming about... except strong type checking:-)

answered Jul 13, 2017 at 5:35

Dmitriy Pichugin

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Comments

Rebse · Accepted Answer · 2013-04-18 21:32:36Z

Beside the two syntax errors - missing ';' after println.. and trailing '*' after closing project tag - you should upgrade your ant installation to a version >= 1.7.x in conjunction with jdk >= 6 to be able to use the builtin javascript engine.
When using jdk >=6 the use of println is no problem, see :

import javax.script.*;
public class ExecuteJS {
 public static void main(String[] args) throws Exception {
 ScriptEngineManager factory = new ScriptEngineManager();
 ScriptEngine engine = factory.getEngineByName("JavaScript");
 engine.eval("print('Line1')");
 engine.eval("println('Line2')");
 engine.eval("print('Line3')");
 engine.eval("println('Line4')");
 }
}

output :

Line1Line2
Line3Line4

and

<project>
 <script language="javascript">
  println("hello, world");
 </script>
</project>

But further testing with Ant 1.9.0 / Win7 (my linux box is down right now) / jdk1.7.0_21 revealed some oddities :

<project>
 <script language="javascript">
  println("hello, world");
 </script>
</project>

works

<project default="foo">
<target name="foo"> 
 <script language="javascript">
  println("hello, world");
 </script>
</target>
</project>

works also

<project name="whatever" default="foo">
<target name="foo"> 
 <script language="javascript">
  println("hello, world");
 </script>
</target>
</project>

works also, whereas

<project name="java" default="foo">
<target name="foo"> 
 <script language="javascript">
  println("hello, world");
 </script>
</target>
</project>

results in

BUILD FAILED
javax.script.ScriptException: sun.org.mozilla.javascript.internal.EcmaError: TypeError: Cannot read property "PrintWriter" from undefined (print#8) in print at line number 8

Strange !?
Seems like a bug, so finally upgrade ant >= 1.7.x and jdk >= 1.6 and
don't use 'java' in name attribute of project :-)

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