com.github.triceo.robozonky.ExtensionsManager Maven / Gradle / Ivy

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/*
 * Copyright 2017 Lukáš Petrovický
 *
 * 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 com.github.triceo.robozonky;

import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.Collection;
import java.util.ServiceLoader;

import com.github.triceo.robozonky.util.FileUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Ensures that all extensions, available in the current working directory's "extensions/" subdirectory, will be on
 * the classpath.
 *
 * All extension points implementing {@link ServiceLoader} must call this class to retrieve the instance.
 */
public enum ExtensionsManager {

    INSTANCE; // cheap thread-safe singleton

    ClassLoader retrieveExtensionClassLoader(final File extensionsFolder) {
        this.LOGGER.debug("Using extensions folder: '{}'.", extensionsFolder.getAbsolutePath());
        final Collection urls =
                FileUtils.filesToUrls(extensionsFolder.listFiles(f -> f.getPath().toLowerCase().endsWith(".jar")));
        return new URLClassLoader(urls.toArray(new URL[urls.size()]));
    }

    ClassLoader retrieveExtensionClassLoader() {
        this.LOGGER.info("Looking up extensions.");
        return FileUtils.findFolder("extensions")
                .map(this::retrieveExtensionClassLoader)
                .orElseGet(() -> {
                    this.LOGGER.debug("Extensions folder not found.");
                    return ExtensionsManager.class.getClassLoader();
                });
    }

    private final Logger LOGGER = LoggerFactory.getLogger(ExtensionsManager.class);
    private final ClassLoader extensionClassLoader;

    ExtensionsManager() {
        this. extensionClassLoader = this.retrieveExtensionClassLoader();
    }

    public  ServiceLoader getServiceLoader(final Class serviceClass) {
        this.LOGGER.debug("Retrieving service loader for '{}'.", serviceClass);
        return ServiceLoader.load(serviceClass, this.extensionClassLoader);
    }

}