/* * 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. * * See the NOTICE file distributed with this work for additional * information regarding copyright ownership. */ package org.seaborne.delta.server.system; import java.util.ArrayList ; import java.util.List ; import java.util.ServiceLoader ; /** Implementation of {@link SubsystemRegistry} for use in the simple * but common case of running Delta as a collection of jars * on the classpath. * <p> * Uses {@link ServiceLoader} to find sub-systems. */ public class SubsystemRegistryBasic<T> implements SubsystemRegistry<T> { private List<T> registry = new ArrayList<>() ; private Object registryLock = new Object() ; private Class<T> classAtRuntime; public SubsystemRegistryBasic(Class<T> cls) { classAtRuntime = cls; } @Override public void load() { synchronized (registryLock) { // Find subsystems asking for initialization. ServiceLoader<T> sl = // Use this->classloader form : better for OSGi ServiceLoader.load(classAtRuntime, this.getClass().getClassLoader()) ; sl.forEach(this::add) ; } } @Override public void add(T module) { synchronized (registryLock) { if ( ! registry.contains(module) ) registry.add(module); } } @Override public boolean isRegistered(T module) { synchronized (registryLock) { return registry.contains(module); } } @Override public void remove(T module) { synchronized (registryLock) { registry.remove(module); } } @Override public int size() { synchronized (registryLock) { return registry.size(); } } @Override public boolean isEmpty() { synchronized (registryLock) { return registry.isEmpty(); } } @Override public List<T> snapshot() { synchronized (registryLock) { return new ArrayList<>(registry) ; } } }