JRubyRegistrarImpl.java

/*
 * Copyright 2011 Leonid Maslov<leonidms@gmail.com>
 *
 * 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 com.galeoconsulting.leonardinius.jruby;

import com.atlassian.sal.api.user.UserManager;
import com.galeoconsulting.leonardinius.api.Registrar;
import com.galeoconsulting.leonardinius.api.ScriptService;
import org.jruby.embed.PropertyName;
import org.jruby.embed.jsr223.JRubyEngineFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;

import javax.script.ScriptEngine;

/**
 * User: leonidmaslov
 * Date: 3/13/11
 * Time: 12:37 AM
 */
public class JRubyRegistrarImpl implements Registrar, InitializingBean, DisposableBean {
// ------------------------------ FIELDS ------------------------------

    private final ScriptService scriptService;
    private final JRubyEngineFactory engineFactory;
    private final Object lock = new Object();

    private ClassLoader chainedClassLoader;

// --------------------------- CONSTRUCTORS ---------------------------

    public JRubyRegistrarImpl(ScriptService scriptService) {
        /* the following property is necessary for ruby, otherwise we can't retrieve the variables set in ruby
               http://yokolet.galeoconsulting.com/2009/08/redbridge-and-jruby-embed-api-update.html
        */
        System.setProperty("org.jruby.embed.localvariable.behavior", "persistent");
        this.scriptService = scriptService;
        engineFactory = new JRubyEngineFactory() {
            @Override
            public ScriptEngine getScriptEngine() {
                System.setProperty(PropertyName.CLASSLOADER.toString(), "context");

                ClassLoader originalContextClassLoader = Thread.currentThread().getContextClassLoader();
                Thread.currentThread().setContextClassLoader(getClassLoader());
                try {
                    return super.getScriptEngine();
                } finally {
                    Thread.currentThread().setContextClassLoader(originalContextClassLoader);
                }
            }
        };
    }

    private ClassLoader getClassLoader() {
        if (chainedClassLoader == null) {
            synchronized (lock) {
                if (chainedClassLoader == null) {
                    chainedClassLoader = this.scriptService.getClassLoader(
                            getClass().getClassLoader(),
                            JRubyEngineFactory.class.getClassLoader(),
                            UserManager.class.getClassLoader(),
                            ClassLoader.getSystemClassLoader());
                }
            }
        }
        return chainedClassLoader;
    }

// ------------------------ INTERFACE METHODS ------------------------


// --------------------- Interface DisposableBean ---------------------

    @Override
    public void destroy() throws Exception {
        scriptService.removeEngine(engineFactory);
    }

// --------------------- Interface InitializingBean ---------------------

    @Override
    public void afterPropertiesSet() throws Exception {
        scriptService.defaultRegistration(engineFactory);
    }
}