OsgiScriptingEngines.java

/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.camunda.bpm.extension.osgi.scripting.impl;

import java.util.Collection;
import java.util.logging.Logger;

import javax.script.ScriptEngine;

import org.camunda.bpm.engine.ProcessEngineException;
import org.camunda.bpm.engine.impl.scripting.engine.ScriptBindingsFactory;
import org.camunda.bpm.engine.impl.scripting.engine.ScriptingEngines;
import org.camunda.bpm.extension.osgi.scripting.ScriptEngineResolver;
import org.osgi.framework.BundleContext;
import org.osgi.framework.FrameworkUtil;
import org.osgi.framework.InvalidSyntaxException;
import org.osgi.framework.ServiceReference;

/**
 * @author Tijs Rademakers
 * @author Ronny Bräunlich
 */
public class OsgiScriptingEngines extends ScriptingEngines {

	private static final Logger LOGGER = Logger
			.getLogger(OsgiScriptingEngines.class.getName());

	private BundleContext context;

	public OsgiScriptingEngines(ScriptBindingsFactory scriptBindingsFactory) {
		super(scriptBindingsFactory);
	}
	
	@Override
	public ScriptEngine getScriptEngineForLanguage(String language) {
    ScriptEngine scriptEngine = null;
    try {
      scriptEngine = resolveScriptEngine(language);
    } catch (InvalidSyntaxException e) {
      throw new ProcessEngineException(
          "problem resolving scripting engine" + e.getMessage(), e);
    }

    if (scriptEngine == null) {
      throw new ProcessEngineException(
          "Can't find scripting engine for '" + language + "'");
    }
    return scriptEngine;
	}

	protected BundleContext getBundleContext() {
		if (context == null) {
			context = FrameworkUtil.getBundle(getClass()).getBundleContext();
		}
		return context;
	}

	ScriptEngine resolveScriptEngine(String scriptEngineName)
			throws InvalidSyntaxException {
		Collection<ServiceReference<ScriptEngineResolver>> refs = getBundleContext().getServiceReferences(
				ScriptEngineResolver.class, null);
		if (refs == null) {
			LOGGER.info("No OSGi script engine resolvers available!");
			return null;
		}

		LOGGER.fine("Found " + refs.size()
				+ " OSGi ScriptEngineResolver services");

		for (ServiceReference<ScriptEngineResolver> ref : refs) {
      ScriptEngineResolver resolver = getBundleContext().getService(ref);
			ScriptEngine engine = resolver
					.resolveScriptEngine(scriptEngineName);
			getBundleContext().ungetService(ref);
			LOGGER.fine("OSGi resolver " + resolver + " produced "
					+ scriptEngineName + " engine " + engine);
			if (engine != null) {
				return engine;
			}
		}
		return null;
	}
}