ClassLoaderUtil.java

/**
 * OpenSpotLight - Open Source IT Governance Platform
 *
 * Copyright (c) 2009, CARAVELATECH CONSULTORIA E TECNOLOGIA EM INFORMATICA LTDA
 * or third-party contributors as indicated by the @author tags or express
 * copyright attribution statements applied by the authors.  All third-party
 * contributions are distributed under license by CARAVELATECH CONSULTORIA E
 * TECNOLOGIA EM INFORMATICA LTDA.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * See the GNU Lesser General Public License  for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 *
 ***********************************************************************
 * OpenSpotLight - Plataforma de Governança de TI de Código Aberto
 *
 * Direitos Autorais Reservados (c) 2009, CARAVELATECH CONSULTORIA E TECNOLOGIA
 * EM INFORMATICA LTDA ou como contribuidores terceiros indicados pela etiqueta
 * @author ou por expressa atribuição de direito autoral declarada e atribuída pelo autor.
 * Todas as contribuições de terceiros estão distribuídas sob licença da
 * CARAVELATECH CONSULTORIA E TECNOLOGIA EM INFORMATICA LTDA.
 *
 * Este programa é software livre; você pode redistribuí-lo e/ou modificá-lo sob os
 * termos da Licença Pública Geral Menor do GNU conforme publicada pela Free Software
 * Foundation.
 *
 * Este programa é distribuído na expectativa de que seja útil, porém, SEM NENHUMA
 * GARANTIA; nem mesmo a garantia implícita de COMERCIABILIDADE OU ADEQUAÇÃO A UMA
 * FINALIDADE ESPECÍFICA. Consulte a Licença Pública Geral Menor do GNU para mais detalhes.
 *
 * Você deve ter recebido uma cópia da Licença Pública Geral Menor do GNU junto com este
 * programa; se não, escreva para:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */

package org.openspotlight.common.util;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;

/**
 * The Class ClassLoaderUtil.
 * 
 * @author Vitor Hugo Chagas
 */
public class ClassLoaderUtil {

    /**
     * Recursive method used to find all classes in a given directory and subdirs.
     * 
     * @param directory The base directory
     * @param packageName The package name for classes found inside the base directory
     * @return The classes
     * @throws ClassNotFoundException the class not found exception
     */
    private static List<Class<?>> findClasses(final File directory,
                                               final String packageName)
        throws ClassNotFoundException {
        final List<Class<?>> classes = new ArrayList<Class<?>>();
        if (!directory.exists()) { return classes; }
        final File[] files = directory.listFiles();
        for (final File file: files) {
            if (file.isDirectory()) {
                assert !file.getName().contains(".");
                classes.addAll(findClasses(file, packageName + "." + file.getName()));
            } else if (file.getName().endsWith(".class")) {
                classes.add(Class.forName(packageName + '.' + file.getName().substring(0, file.getName().length() - 6)));
            }
        }
        return classes;
    }

    /**
     * Method used to check is some class exists at JVM.
     * 
     * @param className The class name to check if it is already lives on JVM.
     * @return True is class exists, False otherwise.
     */
    public static boolean existsClass(final String className) {
        try {
            Class.forName(className);
            return true;
        } catch (final ClassNotFoundException e) {
            return false;
        }
    }

    /**
     * Method used to return some class that exists at JVM.
     * 
     * @param className The class name.
     * @return If class exists returns it, otherwise returns null.
     */
    public static Class<?> getClass(final String className) {
        try {
            return Class.forName(className);
        } catch (final ClassNotFoundException e) {
            return null;
        }
    }

    /**
     * Scans all classes accessible from the context class loader which belong to the given package and subpackages.
     * 
     * @param packageName The base package
     * @return The classes
     * @throws ClassNotFoundException the class not found exception
     * @throws IOException Signals that an I/O exception has occurred.
     */
    public static Class<?>[] getClasses(final String packageName)
        throws ClassNotFoundException, IOException {
        final ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        assert classLoader != null;
        final String path = packageName.replace('.', '/');
        final Enumeration<URL> resources = classLoader.getResources(path);
        final List<File> dirs = new ArrayList<File>();
        while (resources.hasMoreElements()) {
            final URL resource = resources.nextElement();
            dirs.add(new File(resource.getFile()));
        }
        final ArrayList<Class<?>> classes = new ArrayList<Class<?>>();
        for (final File directory: dirs) {
            classes.addAll(findClasses(directory, packageName));
        }
        return classes.toArray(new Class[classes.size()]);
    }

}