org.microtitan.diffusive.utils.ClassLoaderUtils.java Source code

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Here is the source code for org.microtitan.diffusive.utils.ClassLoaderUtils.java

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/*
 * Copyright 2012 Robert Philipp
 * 
 * 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.microtitan.diffusive.utils;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLClassLoader;

import org.apache.commons.io.IOUtils;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.apache.log4j.xml.DOMConfigurator;
import org.microtitan.diffusive.Constants;

/**
 * Utilities for converting a {@link Class}, reference by name, into a {@code byte[]} for transporting
 * across the network. The {@link #loadClassToByteArray(String)} method uses the application
 * class loader and the application's class path to search for the {@link Class} file and load it
 * as a resource. The {@link #loadClassToByteArray(String, URLClassLoader)} uses the specified
 * {@link URLClassLoader} to search the JAR files held in the {@link URLClassLoader} and loads the
 * {@link Class} file as a resource from that JAR.
 * 
 * @author Robert Philipp
 */
public class ClassLoaderUtils {

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

    /**
     * Converts the {@link Class} into a {@code byte[]}.
     * @param className The name of the {@link Class} to convert into a {@code byte[]}
     * @return a {@code byte[]} representation of the {@link Class}
     */
    public static byte[] loadClassToByteArray(final String className) {
        byte[] bytes = null;
        try {
            // mangle the class name as specified by the ClassLoader.getSystemResourceAsStream docs
            final String classAsPath = className.replace('.', '/') + ".class";

            // grab the input stream
            final InputStream input = ClassLoader.getSystemResourceAsStream(classAsPath);

            // convert to bytes if the input stream exists
            if (input != null) {
                bytes = IOUtils.toByteArray(input);
            }
        } catch (IOException e) {
            final StringBuilder message = new StringBuilder();
            message.append("Error writing out to the Class< ? > to a byte array.").append(Constants.NEW_LINE)
                    .append("  Class: ").append(className);
            LOGGER.error(message.toString(), e);
            throw new IllegalStateException(message.toString(), e);
        }

        return bytes;
    }

    /**
     * Converts the {@link Class} into a {@code byte[]}. The method allows you to load a {@link Class} file,
     * as a resource,that is found in a JAR file.
     * @param className The name of the {@link Class} to convert into a {@code byte[]}
     * @param classLoader The {@link URLClassLoader} that is to be used to load the {@link Class} with the specified
      *                    name
      * @return a {@code byte[]} representation of the {@link Class}
     */
    public static byte[] loadClassToByteArray(final String className, final URLClassLoader classLoader) {
        byte[] bytes = null;
        try {
            // mangle the class name as specified by the ClassLoader.getSystemResourceAsStream docs
            final String classAsPath = className.replace('.', '/') + ".class";

            // grab the input stream
            InputStream input = classLoader.getResourceAsStream(classAsPath);
            if (input == null) {
                input = classLoader.getResourceAsStream("/" + classAsPath);
            }

            // convert to bytes if the input stream exists
            if (input != null) {
                bytes = IOUtils.toByteArray(input);
            }
        } catch (IOException e) {
            final StringBuilder message = new StringBuilder();
            message.append("Error writing out to the Class< ? > to a byte array.").append(Constants.NEW_LINE)
                    .append("  Class: ").append(className);
            LOGGER.error(message.toString(), e);
            throw new IllegalStateException(message.toString(), e);
        }

        return bytes;
    }

    public static void main(String[] args) throws IOException {
        // set the logging level
        DOMConfigurator.configure("log4j.xml");
        Logger.getRootLogger().setLevel(Level.DEBUG);

        final String classname = "org.microtitan.tests.threaded.MultiThreadedCalc";
        final byte[] systemBytes = loadClassToByteArray(classname);
        if (systemBytes == null) {
            System.out.println("null");
        } else {
            System.out.println(systemBytes.length);
        }

        final URL url = new URL("file", null,
                "///C:/Users/desktop/workspace/diffusive/Diffusive_v0.2.0/examples/example_0.2.0.jar");
        //      final URL url = new URL( "file", null, "/Users/rob/Documents/workspace/diffusive/Diffusive_v0.2.0/examples/example_0.2.0.jar" );
        System.out.println(url.toString());
        final URLClassLoader urlClassLoader = new URLClassLoader(new URL[] { url });
        final byte[] urlBytes = loadClassToByteArray(classname, urlClassLoader);
        if (urlBytes == null) {
            System.out.println("null");
        } else {
            System.out.println(urlBytes.length);
        }

        final InputStream input = urlClassLoader.getResourceAsStream(classname.replace('.', '/') + ".class");
        if (input == null) {
            System.out.println("null");
        } else {
            System.out.println(IOUtils.toByteArray(input).length);
        }
        urlClassLoader.close();

        //      final String className = BeanTest.class.getName();
        //      byte[] bytes = convertClassToByteArray( className );
        //      
        //      Class< ? > clazz = new RestfulClassLoader( null, ClassLoaderUtils.class.getClassLoader() ).getClazz( className, bytes );
        //      try
        //      {
        //         final Method method = clazz.getMethod( "print" );
        //         method.invoke( clazz.newInstance() );
        //      }
        //      catch( IllegalAccessException | NoSuchMethodException | SecurityException | IllegalArgumentException | InvocationTargetException | InstantiationException e )
        //      {
        //         e.printStackTrace();
        //      }
        //      
        //      System.out.println( clazz.getName() );
    }
}