com.arangodb.shaded.vertx.core.ServiceHelper Maven / Gradle / Ivy
/*
* Copyright (c) 2011-2019 Contributors to the Eclipse Foundation
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
* which is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
*/
package com.arangodb.shaded.vertx.core;
import java.util.*;
/**
* A helper class for loading factories from the classpath.
*
* @author Tim Fox
*/
public class ServiceHelper {
public static T loadFactory(Class clazz) {
T factory = loadFactoryOrNull(clazz);
if (factory == null) {
throw new IllegalStateException("Cannot find META-INF/services/" + clazz.getName() + " on classpath");
}
return factory;
}
public static T loadFactoryOrNull(Class clazz) {
Collection collection = loadFactories(clazz);
if (!collection.isEmpty()) {
return collection.iterator().next();
} else {
return null;
}
}
public static Collection loadFactories(Class clazz) {
return loadFactories(clazz, null);
}
public static Collection loadFactories(Class clazz, ClassLoader classLoader) {
List list = new ArrayList<>();
ServiceLoader factories;
if (classLoader != null) {
factories = ServiceLoader.load(clazz, classLoader);
} else {
// this is equivalent to:
// ServiceLoader.load(clazz, TCCL);
factories = ServiceLoader.load(clazz);
}
if (factories.iterator().hasNext()) {
factories.iterator().forEachRemaining(list::add);
return list;
} else {
// By default ServiceLoader.load uses the TCCL, this may not be enough in environment dealing with
// classloaders differently such as OSGi. So we should try to use the classloader having loaded this
// class. In OSGi it would be the bundle exposing vert.x and so have access to all its classes.
factories = ServiceLoader.load(clazz, ServiceHelper.class.getClassLoader());
if (factories.iterator().hasNext()) {
factories.iterator().forEachRemaining(list::add);
return list;
} else {
return Collections.emptyList();
}
}
}
}