JavaScriptTransformationService.java

/**
 * Copyright (c) 2014-2017 by the respective copyright holders.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package org.eclipse.smarthome.transform.javascript.internal;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStreamReader;
import java.io.Reader;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

import org.apache.commons.io.IOUtils;
import org.eclipse.smarthome.config.core.ConfigConstants;
import org.eclipse.smarthome.core.transform.TransformationException;
import org.eclipse.smarthome.core.transform.TransformationService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * The implementation of {@link TransformationService} which transforms the
 * input by Java Script.
 * 
 * @author Pauli Anttila
 */
public class JavaScriptTransformationService implements TransformationService {

    /**
     * Transforms the input <code>source</code> by Java Script. It expects the
     * transformation rule to be read from a file which is stored under the
     * 'configurations/transform' folder. To organize the various
     * transformations one should use subfolders.
     * 
     * @param filename
     *            the name of the file which contains the Java script
     *            transformation rule. Transformation service inject input
     *            (source) to 'input' variable.
     * @param source
     *            the input to transform
     */
    @Override
    public String transform(String filename, String source) throws TransformationException {
        Logger logger = LoggerFactory.getLogger(JavaScriptTransformationService.class);
        if (filename == null || source == null) {
            throw new TransformationException("the given parameters 'filename' and 'source' must not be null");
        }

        logger.debug("about to transform '{}' by the Java Script '{}'", source, filename);

        Reader reader;

        try {
            String path = ConfigConstants.getConfigFolder() + File.separator
                    + TransformationService.TRANSFORM_FOLDER_NAME + File.separator + filename;
            reader = new InputStreamReader(new FileInputStream(path));
        } catch (FileNotFoundException e) {
            throw new TransformationException("An error occurred while loading script.", e);
        }

        ScriptEngineManager manager = new ScriptEngineManager();

        ScriptEngine engine = manager.getEngineByName("javascript");
        engine.put("input", source);

        Object result = null;

        long startTime = System.currentTimeMillis();

        try {
            result = engine.eval(reader);
        } catch (ScriptException e) {
            throw new TransformationException("An error occurred while executing script.", e);
        } finally {
            IOUtils.closeQuietly(reader);
        }

        logger.trace("JavaScript execution elapsed {} ms", System.currentTimeMillis() - startTime);

        return String.valueOf(result);
    }

}