io.atlasmap.java.inspect.ClassFinder Maven / Gradle / Ivy

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/**
 * Copyright (C) 2017 Red Hat, Inc.
 *
 * 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.atlasmap.java.inspect;

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

/**
 * ClassFinder - from: http://stackoverflow.com/questions/15519626/how-to-get-all-classes-names-in-a-package
 */
public class ClassFinder {

    private static final char PKG_SEPARATOR = '.';

    private static final char DIR_SEPARATOR = '/';

    private static final String CLASS_FILE_SUFFIX = ".class";

    private static final String BAD_PACKAGE_ERROR = "Unable to get resources from path '%s'. Are you sure the package '%s' exists?";

    public static List> find(String scannedPackage) {
        String scannedPath = scannedPackage.replace(PKG_SEPARATOR, DIR_SEPARATOR);
        URL scannedUrl = Thread.currentThread().getContextClassLoader().getResource(scannedPath);
        if (scannedUrl == null) {
            throw new IllegalArgumentException(String.format(BAD_PACKAGE_ERROR, scannedPath, scannedPackage));
        }
        File scannedDir = new File(scannedUrl.getFile());
        List> classes = new ArrayList>();
        for (File file : scannedDir.listFiles()) {
            classes.addAll(find(file, scannedPackage));
        }
        return classes;
    }

    private static List> find(File file, String scannedPackage) {
        List> classes = new ArrayList>();
        String resource = scannedPackage + PKG_SEPARATOR + file.getName();
        if (file.isDirectory()) {
            for (File child : file.listFiles()) {
                classes.addAll(find(child, resource));
            }
        } else if (resource.endsWith(CLASS_FILE_SUFFIX)) {
            int endIndex = resource.length() - CLASS_FILE_SUFFIX.length();
            String className = resource.substring(0, endIndex);
            try {
                classes.add(Class.forName(className));
            } catch (ClassNotFoundException ignore) {
            }
        }
        return classes;
    }

}