eu.stratosphere.nephele.util.ClassUtils.java Source code

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Here is the source code for eu.stratosphere.nephele.util.ClassUtils.java

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/***********************************************************************************************************************
 *
 * Copyright (C) 2010 by the Stratosphere project (http://stratosphere.eu)
 *
 * 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 eu.stratosphere.nephele.util;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import eu.stratosphere.nephele.fs.FileSystem;
import eu.stratosphere.nephele.protocols.VersionedProtocol;
import eu.stratosphere.nephele.types.Record;

/**
 * Utility class which provides various methods for dynamic class loading.
 * 
 * @author warneke
 */
public final class ClassUtils {

    /**
     * The log object used for debugging.
     */
    private static final Log LOG = LogFactory.getLog(ClassUtils.class);

    /**
     * Private constructor used to overwrite public one.
     */
    private ClassUtils() {
    }

    /**
     * Searches for a protocol class by its name and attempts to load it.
     * 
     * @param className
     *        the name of the protocol class
     * @return an instance of the protocol class
     * @throws ClassNotFoundException
     *         thrown if no class with such a name can be found
     */
    // TODO: See if we can improve type safety here
    @SuppressWarnings("unchecked")
    public static Class<? extends VersionedProtocol> getProtocolByName(final String className)
            throws ClassNotFoundException {

        if (!className.contains("Protocol")) {
            throw new ClassNotFoundException("Only use this method for protocols!");
        }

        return (Class<? extends VersionedProtocol>) Class.forName(className, true, getClassLoader());
    }

    /**
     * Searches for a record class by its name and attempts to load it.
     * 
     * @param className
     *        the name of the record class
     * @return an instance of the record class
     * @throws ClassNotFoundException
     *         thrown if no class with such a name can be found
     */
    // TODO: See if we can improve type safety here
    @SuppressWarnings("unchecked")
    public static Class<? extends Record> getRecordByName(final String className) throws ClassNotFoundException {

        return (Class<? extends Record>) Class.forName(className, true, getClassLoader());

    }

    /**
     * Searches for a file system class by its name and attempts to load it.
     * 
     * @param className
     *        the name of the file system class
     * @return an instance of the file system class
     * @throws ClassNotFoundException
     *         thrown if no class with such a name can be found
     */
    // TODO: See if we can improve type safety here
    @SuppressWarnings("unchecked")
    public static Class<? extends FileSystem> getFileSystemByName(final String className)
            throws ClassNotFoundException {

        return (Class<? extends FileSystem>) Class.forName(className, true, getClassLoader());
    }

    /**
     * Returns the thread's default class loader.
     * 
     * @return the thread's default class loader
     */
    public static ClassLoader getClassLoader() {

        final ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        if (classLoader == null) {
            LOG.fatal("classLoader is null");
        }

        return classLoader;
    }
}