NashornIntegration

The Nashorn module is used to run JavaScript on the server side by posting a script to an ResourceReference which is intended to execute it.

Before the script is actually executed it is translated into an AST (Abstract Syntax Tree) and abort statements are injected to prevent the script to run endless. If the script hits the maximum run duration the thread which executes it is going to be interrupted and all loops and function calls are going to be skipped.

Another feature is that you are able to monitor the actual allocated bytes of the thread which runs the script and abort the process if a given amount of memory is exceeded.

Setup

WebApplication

public class NashornApplication extends WebApplication
{

	private static NashornObject nashornObject = new NashornObject();

	@Override
	public Class<? extends Page> getHomePage()
	{
		return NashornPage.class;
	}

	@Override
	protected void init()
	{
		// Initial thread pool of 10 concurrent scripts
		// Maximum run duration 5 Seconds
		// Memory check interval 10 seconds (optional)
		// Allowed memory 31457280 => 30mb (optional, but requires check interval)
		mountResource("/nashorn", new NashornResourceReference("nashorn", 10, 5, TimeUnit.SECONDS,
			10, TimeUnit.MILLISECONDS, 31457280)
		{

			private static final long serialVersionUID = 1L;

			@Override
			protected void setup(Attributes attributes, Bindings bindings)
			{
				// which objects are going to be accessable
				bindings.put("nashornObject", nashornObject); 
			}

			@Override
			protected Writer getWriter()
			{
				// Where to write output
				return new BufferedWriter(new OutputStreamWriter(System.out)); 
			}

			@Override
			protected Writer getErrorWriter()
			{
				// Where to write errors
				return new BufferedWriter(new OutputStreamWriter(System.out));
			}

			@Override
			protected boolean isDebug()
			{
				// Outputs AST information and other stuff while executing the actual script
				return true;
			}

			protected ClassFilter getClassFilter()
			{
				// default is to allow nothing!
				return new ClassFilter()
				{
					@Override
					public boolean exposeToScripts(String name)
					{
						// which classes are allowed to be accessed (name is full qualified)
						return false; 
					}
				};
			}

		});
	}
}