1 /* 2 * Copyright (C) 2015 Google, Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 package dagger.producers.monitoring.internal; 17 18 import dagger.producers.monitoring.ProductionComponentMonitor; 19 import java.util.Set; 20 import java.util.logging.Level; 21 import java.util.logging.Logger; 22 import javax.inject.Provider; 23 24 /** 25 * A class that provides a {@link ProductionComponentMonitor} for use in production components. 26 * 27 * <p>This caches the underlying the monitor, since we want a single instance for each component. 28 */ 29 public final class MonitorCache { 30 private static final Logger logger = Logger.getLogger(MonitorCache.class.getName()); 31 32 private volatile ProductionComponentMonitor monitor; 33 34 /** 35 * Returns the underlying monitor. This will only actually compute the monitor the first time it 36 * is called; subsequent calls will simply return the cached value, so the arguments to this 37 * method are ignored. It is expected (though not checked) that this method is called with 38 * equivalent arguments each time (like a {@link dagger.Provides @Provides} method would). 39 */ 40 public ProductionComponentMonitor monitor( 41 Provider<?> componentProvider, 42 Provider<Set<ProductionComponentMonitor.Factory>> monitorFactorySetProvider) { 43 ProductionComponentMonitor result = monitor; 44 if (result == null) { 45 synchronized (this) { 46 result = monitor; 47 if (result == null) { 48 try { 49 ProductionComponentMonitor.Factory factory = 50 Monitors.delegatingProductionComponentMonitorFactory( 51 monitorFactorySetProvider.get()); 52 result = monitor = factory.create(componentProvider.get()); 53 } catch (RuntimeException e) { 54 logger.log(Level.SEVERE, "RuntimeException while constructing monitor factories.", e); 55 result = monitor = Monitors.noOpProductionComponentMonitor(); 56 } 57 } 58 } 59 } 60 return result; 61 } 62 } 63
