RhinoInterpreter.java

package org.aitools.programd.interpreter;

import org.apache.log4j.Logger;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.Scriptable;

/**
 * An implementation of {@link org.aitools.programd.interpreter.Interpreter} that handles server-side JavaScript using
 * the Rhino package.
 * 
 * @author Jon Baer
 * @author <a href="mailto:noel@aitools.org">Noel Bush</a>
 */
public class RhinoInterpreter implements Interpreter {

  /** The logger. */
  private static final Logger logger = Logger.getLogger("programd");

  /**
   * @see org.aitools.programd.interpreter.Interpreter#evaluate(java.lang.String)
   */
  @Override
  public String evaluate(String expression) {
    logger.debug("evaluate: \"" + expression + "\"");
    Context context;
    try {
      context = Context.enter();
    }
    // If the Rhino js library is somehow missing....
    catch (NoClassDefFoundError e) {
      logger.error("Rhino JavaScript library is missing!", e);
      return "";
    }
    Scriptable scope = context.initStandardObjects(null);

    Object result = null;
    try {
      result = context.evaluateString(scope, expression, "<cmd>", 1, null);
    }
    catch (Exception e) {
      logger.warn(String.format(
          "JavaScript exception (see interpreter log).%nGot exception:%n%s%nwhen processing:%n%s", e, expression));
    }
    Context.exit();
    if (result != null) {
      return result.toString();
    }
    // (otherwise...)
    logger.info("JavaScript returned null!");
    return "";
  }
}