Java example source code file (CopyClassFile.java)

This example Java source code file (CopyClassFile.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

classloader, copyclassfile, could, file, fileinputstream, illegalargumentexception, inputstream, ioexception, net, network, path, runtimeexception, string, url, util

The CopyClassFile.java Java example source code

/*
 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
import java.util.Arrays;

/**
 * A utility to copy the class and all it's inner classes to the specified directory.
 * <p>
 * Usage in jtreg:
 *
 * @build CopyClassFile
 * @run main CopyClassFile package.class dest_directory
 */
public class CopyClassFile {

    private static final ClassLoader cl = CopyClassFile.class.getClassLoader();

    private static String destinationDir;
    private static String className;
    private static String classFile;

    public static void main(String[] args) throws Exception {
        if (args.length != 2) {
            throw new IllegalArgumentException("Illegal usage: class name and destination directory should be specified");
        }

        destinationDir = args[1];
        className = args[0];
        classFile = className.replaceAll("\\.", File.separator) + ".class";

        URL url = cl.getResource(classFile);
        if (url == null) {
            throw new RuntimeException("Could not find a class: " + classFile);
        }

        File[] files = new File(url.toURI())
                .getParentFile()
                .listFiles((dir, name) -> name.startsWith(cutPackageName(className)) && name.endsWith(".class"));

        Arrays.stream(files).forEach(CopyClassFile::copyFile);
    }

    private static String cutPackageName(String className) {
        int dotIndex = className.lastIndexOf(".") + 1;
        if (dotIndex <= 0) {
            return className;
        } else {
            return className.substring(dotIndex);
        }
    }

    private static void copyFile(File f) {
        try {
            Path classFilePath = Paths.get(classFile);
            String packagePath = classFilePath.getParent() == null ? "" : classFilePath.getParent().toString();
            Path p = Paths.get(destinationDir + packagePath + File.separator + f.getName());
            Files.createDirectories(p.getParent());
            try (InputStream is = new FileInputStream(f)) {
                Files.copy(is, p, StandardCopyOption.REPLACE_EXISTING);
            }
        } catch (IOException ex) {
            throw new RuntimeException("Could not copy file " + f, ex);
        }
    }
}