io.github.rmuhamedgaliev.ClassFinder Maven / Gradle / Ivy

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/*
 *     Copyright 2015 Rinat Muhamedgaliev
 *
 *     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 io.github.rmuhamedgaliev;

import java.io.File;
import java.io.FileInputStream;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.stream.Stream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

/**
 * Follow class provide ability retrieve classes from jar directory and find
 * extended classes
 *
 * @author Rinat Muhamedgaliev
 */
public class ClassFinder {
//    Path of get jars for build list files
    private final static Path PLUGIN_PATH = Paths.get("plugins/");
    private ArrayList pluginList = new ArrayList();

    /**
     * Find and build plugin list
     * @param klass any {@link Class} for search extended classes
     * @return {@link ArrayList} of classes extended of klass
     * @throws Exception
     * 
     *     When not found {@link ClassFinder#PLUGIN_PATH} in working directory
     *     If can't access to classes from jar file
     * 
     */
    public ArrayList loadPlugins(Class klass) throws Exception {
        listFiles(PLUGIN_PATH).forEach(p -> {
            try {
                getPluginList(p.toFile(), klass);
            } catch (Exception e) {
                e.printStackTrace();
            }
        });
        return pluginList;
    }

    /**
     * Simple recursive retrieve directory
     * @param path path of start get structure
     * @return labda based {@link Stream} of {@link Path} objects
     */
    private static Stream listFiles(Path path) {
        if (Files.isDirectory(path)) {
            try {
                return Files.list(path).flatMap(ClassFinder::listFiles);
            } catch (Exception e) {
                return Stream.empty();
            }
        } else {
            return Stream.of(path);
        }
    }

    /**
     * Follow method retrieve classes from jar file and find all extended classes
     *
     * @param file jar archived file with compiled classes
     * @param klass pattern class for find extended classes
     * @throws Exception
     * 
     *     When not found {@link ClassFinder#PLUGIN_PATH} in working directory
     *     If can't access to classes from jar file
     * 
     */
    private void getPluginList(File file, Class klass) throws Exception {
        if (file.isFile()) {
            Class pluginClass;
            ZipInputStream zip = new ZipInputStream(new FileInputStream(file));
            for (ZipEntry entry = zip.getNextEntry(); entry != null; entry = zip.getNextEntry()) {
                if (!entry.isDirectory() && entry.getName().endsWith(".class")) {
                    String className = entry.getName().replace('/', '.');
                    className = className.substring(0, className.length() - ".class".length());
                    URL[] urls = {new URL("jar:" + file.toURI().toURL() + "!/")};
                    URLClassLoader cl = new URLClassLoader(urls, Thread.currentThread().getContextClassLoader());
                    pluginClass = cl.loadClass(className);
                    if (pluginClass != null && pluginClass.getSuperclass() != null && pluginClass.getSuperclass().equals(klass)) {
                        pluginList.add(pluginClass.newInstance());
                    }
                }
            }
        }
    }
}