Boilerplate: Scripting API Facade

/**
 * This default implementation tries to create and use a JavaScript script(ing) engine.
 *
 * @author Octavian Theodor NITA
 * @version 1.0, Feb 27, 2012
 */
public class ScriptEngineFacade {
 
    private static final Logger logger = Logger.getLogger(ScriptEngineFacade.class);
 
    private final ScriptEngine scriptEngine = new ScriptEngineManager().getEngineByName("JavaScript");
 
    public void put(String name, Object value) {
        scriptEngine.put(name, value);
    }
 
    public void eval(String scriptName) throws IOException, ScriptException {
        InputStream script = getClass().getClassLoader().getResourceAsStream(scriptName);
        if (script == null) { // cannot find the script in the classpath... try in the file system
            script = new FileInputStream(scriptName);
        }
        try {
            scriptEngine.eval(new InputStreamReader(script));
        } finally {
            try {
                script.close();
            } catch (IOException e) {
                logger.warn("cannot close stream for script " + scriptName + "; ignoring...", e);
            }
        }
    }
 
    public <T> T value(String expr, Class<T> klass) {
        if (klass == null) {
            throw new IllegalArgumentException("cannot cast the value of " + expr + " using a null class name");
        }
        if (expr == null) {
            return null;
        }
 
        try {
            return klass.cast(scriptEngine.eval(expr));
        } catch (NullPointerException e) {
            logger.error("cannot get the value of " + expr + ": a null or undefined reference was encountered", e);
            return null;
        } catch (ClassCastException e) {
            logger.error("cannot get the value of " + expr + ": expected value type for is " + klass.getName(), e);
            return null;
        } catch (ScriptException e) {
            logger.error("cannot get the value of " + expr + ": cannot evaluate expression", e);
            return null;
        }
    }
}