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/*
 * Copyright 2005-2010 the original author or authors.
 * 
 * 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 org.wamblee.inject;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Cache of {@link CdiInjector}s for efficiency to avoid duplicate analysis of a
 * given class.
 * 
 * @author Erik Brakkee
 */
public class InjectorCache {

    private Map injectors;

    private InjectorFactory injectorFactory;

    /**
     * Constructs an empty cache.
     * 
     * @param aInjectorFactory
     *            Injector factory to create Injectors.
     */
    public InjectorCache(InjectorFactory aInjectorFactory) {
        injectorFactory = aInjectorFactory;
        injectors = new ConcurrentHashMap();
    }

    /**
     * Gets the injector for a given class. This returns a cached injector or
     * creates a new injector and caches it.
     * 
     * @param aClass
     *            Class to find injector for.
     * @return Injector.
     */
    public Injector getInjector(Class aClass) {
        Injector injector = injectors.get(aClass.getName());
        if (injector == null) {
            // create and add injector
            // NOTE: in rare circumstances this will lead to parallel
            // creation of
            // an injector for the same class. However, only one of them
            // will be the final one
            // in the map. There are no side effects of this duplicate
            // creation of injectors.
            injector = injectorFactory.create(aClass);
            injectors.put(aClass.getName(), injector);
        }
        return injector;
    }
}