Java tutorial
/** * Copyright 2016-2017 Sixt GmbH & Co. Autovermietung KG * 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.sixt.service.framework.injection; import com.google.inject.AbstractModule; import com.google.inject.Injector; import com.google.inject.Provides; import com.sixt.service.framework.MethodHandlerDictionary; import com.sixt.service.framework.ServiceProperties; import com.sixt.service.framework.annotation.ServiceRegistryPlugin; import com.sixt.service.framework.registry.ServiceDiscoveryProvider; import com.sixt.service.framework.registry.ServiceRegistrationProvider; import io.github.lukehutch.fastclasspathscanner.FastClasspathScanner; import org.apache.commons.lang3.StringUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.util.List; public class ServiceRegistryModule extends AbstractModule { private static final Logger logger = LoggerFactory.getLogger(ServiceRegistryModule.class); private final ServiceProperties serviceProperties; private Object plugin; private ServiceRegistrationProvider registrationProvider; private ServiceDiscoveryProvider discoveryProvider; private List<String> serviceRegistryPlugins; public ServiceRegistryModule(ServiceProperties serviceProperties) { this.serviceProperties = serviceProperties; } @Override protected void configure() { } @Provides public ServiceDiscoveryProvider getDiscoveryProvider(Injector injector) { if (discoveryProvider == null) { Object plugin = getServiceRegistryPlugin(injector); if (plugin != null && plugin instanceof ServiceDiscoveryProvider) { discoveryProvider = (ServiceDiscoveryProvider) plugin; } } return discoveryProvider; } @Provides public ServiceRegistrationProvider getRegistrationProvider(Injector injector) { if (registrationProvider == null) { logger.debug("Searching for instance of ServiceRegistrationProvider"); Object plugin = getServiceRegistryPlugin(injector); if (plugin != null && plugin instanceof ServiceRegistrationProvider) { logger.debug("Found ServiceRegistrationProvider: {}", plugin.getClass().getSimpleName()); registrationProvider = (ServiceRegistrationProvider) plugin; ServiceRegistrationProvider provider = (ServiceRegistrationProvider) plugin; MethodHandlerDictionary methodHandlers = injector.getInstance(MethodHandlerDictionary.class); provider.initialize(methodHandlers); } } return registrationProvider; } private Object getServiceRegistryPlugin(Injector injector) { if (plugin == null) { plugin = findServiceRegistryPlugin(injector); } return plugin; } private Object findServiceRegistryPlugin(Injector injector) { Object retval = null; String pluginName = serviceProperties.getProperty("registry"); if (StringUtils.isBlank(pluginName)) { return null; } if (serviceRegistryPlugins == null) { // only scan if not already set serviceRegistryPlugins = new FastClasspathScanner().scan() .getNamesOfClassesWithAnnotation(ServiceRegistryPlugin.class); } boolean found = false; for (String plugin : serviceRegistryPlugins) { try { @SuppressWarnings("unchecked") Class<? extends ServiceRegistryPlugin> pluginClass = (Class<? extends ServiceRegistryPlugin>) Class .forName(plugin); ServiceRegistryPlugin anno = pluginClass.getAnnotation(ServiceRegistryPlugin.class); if (anno != null && pluginName.equals(anno.name())) { retval = injector.getInstance(pluginClass); found = true; break; } } catch (ClassNotFoundException e) { logger.error("ServiceRegistryPlugin not found", e); } } if (!found) { logger.warn("Registry plugin '{}' was not found in the class path", pluginName); } return retval; } public void setServiceRegistryPlugins(List<String> serviceRegistryPlugins) { this.serviceRegistryPlugins = serviceRegistryPlugins; } }