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.ServiceProperties; import com.sixt.service.framework.annotation.ConfigurationPlugin; import com.sixt.service.framework.configuration.ConfigurationProvider; 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 ConfigurationModule extends AbstractModule { private static final Logger logger = LoggerFactory.getLogger(ConfigurationModule.class); private final ServiceProperties serviceProperties; private Object plugin; private ConfigurationProvider provider; private List<String> configurationPlugins; public ConfigurationModule(ServiceProperties serviceProperties) { this.serviceProperties = serviceProperties; } @Override protected void configure() { } @Provides public ConfigurationProvider getProvider(Injector injector) { if (provider == null) { logger.debug("Searching for instance of ConfigurationProvider"); Object plugin = getConfigurationPlugin(injector); if (plugin != null && plugin instanceof ConfigurationProvider) { logger.debug("Found ConfigurationProvider: {}", plugin.getClass().getSimpleName()); provider = (ConfigurationProvider) plugin; } else { logger.info("No ConfigurationProvider will be used."); } } return provider; } private Object getConfigurationPlugin(Injector injector) { if (plugin == null) { plugin = findConfigurationPlugin(injector); } return plugin; } private Object findConfigurationPlugin(Injector injector) { Object retval = null; String pluginName = serviceProperties.getProperty("configuration"); if (StringUtils.isBlank(pluginName)) { return null; } if (configurationPlugins == null) { // only scan if not already set configurationPlugins = new FastClasspathScanner().scan() .getNamesOfClassesWithAnnotation(ConfigurationPlugin.class); } boolean found = false; for (String plugin : configurationPlugins) { try { @SuppressWarnings("unchecked") Class<? extends ConfigurationPlugin> pluginClass = (Class<? extends ConfigurationPlugin>) Class .forName(plugin); ConfigurationPlugin anno = pluginClass.getAnnotation(ConfigurationPlugin.class); if (anno != null && pluginName.equals(anno.name())) { retval = injector.getInstance(pluginClass); found = true; break; } } catch (ClassNotFoundException e) { logger.error("ConfigurationPlugin not found", e); } } if (!found) { logger.warn("Configuration plugin '{}' was not found in the class path", pluginName); } return retval; } public void setConfigurationPlugins(List<String> configurationPlugins) { this.configurationPlugins = configurationPlugins; } }