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Starting Situation

Java 1.8 comes with a different JavaScript engine ("Nashorn") to that included in Java 1.7 ("Rhino"). As JobScheduler can use the JavaScript engine provided with Java for scripts, it is important that users wishing to use Java 1.8 with future JobScheduler releases ensure that their scripts are capable of being executed with the Nashorn engine.

Oracle have published an article describing background and features of their new JavaScript engine:

  • Oracle Nashorn: A Next-Generation JavaScript Engine for the JVM.
  • We recommend JobScheduler users running JavaScript scripts to use this article to update their scripts.
  • One of the most important changes is likely to be that Nashorn does not support the importClass statement. Instead of the importClass statement you can use the class JavaImporter

Differences in Practice

Example for class import

  • Rhino only:
Example: class import with Rhino
 importClass(java.io.File);
 importClass(java.nio.charset.Charset);
  • Rhino and Nashorn:
Example: class import with Rhino and Nashorn
 var imports = new JavaImporter(
     java.io.File,
     java.nio.charset.Charset
 );

Common Usage Example

Example: common usage with Rhino and Nashorn
 with (imports) {
     // usage of File
     // usage of Charset
 }

Multi Engine Script

  • The following script with language javax.script:javascript uses Rhino engine on Java 1.7 and Nashorn engine on Java 1.8 and works on both engines:
Example: multi engine script
 <script language="javax.script:JavaScript">
     <![CDATA[
         var imports = new JavaImporter(
             java.io.File,
             java.nio.charset.Charset
         );
  
         function spooler_process() {
             with (imports) {
                 // usage of File
                 // usage of Charset
             }
             
             // also possible:
             // usage of java.lang.Thread
 
             return true;
         }
 
     ]]>
 </script>

Job Script Changes

  • To make the changeover as smooth as possible, we recommend that users specify that the default JavaScript engine for the Java version is used, i.e. "javax.script:JavaScript" instead of "javax.script:rhino".
  • This will ensure that the changeover of the JavaScript engine will occur at the same time as the changeover to Java 1.8.
  • Please note that at the time of writing it is not yet decided when JobScheduler will become Java 1.8 capable but this is likely to occur towards the end of 2014. Oracle have announced that they will stop updating Java 7 after April 2015.

See also