SingletonBeanFactory.java

package org.theonefx.wcframework.ioc;

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

import org.theonefx.wcframework.core.BeanDefinitionPostProcesser;
import org.theonefx.wcframework.utils.Assert;

class SingletonBeanFactory extends BeanDefinitionPostProcesser {

	/**
	 * null的代替，为了解决ConcurrentHashMap不能存放null的问题
	 */
	protected static final Object NULL_OBJECT = new Object();

	/**
	 * 缓存的单例对象map，用键值对的形式
	 */
	private final Map<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>();

	/**
	 * 出于效率考虑，增加一个set按顺序存放所有单例对象的id
	 */
	private final Set<String> registeredSingletons = new LinkedHashSet<String>(16);

	public void registerSingleton(String beanId, Object singletonObject) throws IllegalStateException {
		Assert.notNull(beanId, "'beanId' 不能为空");
		synchronized (this.singletonObjects) {
			Object oldObject = this.singletonObjects.get(beanId);
			if (oldObject != null) {
				throw new IllegalStateException("无法使用 '" + beanId + "'注册对象 [" + singletonObject + "] : 对象已存在 [" + oldObject + "]");
			}
			addSingleton(beanId, singletonObject);
		}
	}

	private void addSingleton(String beanName, Object singletonObject) {
		synchronized (this.singletonObjects) {
			this.singletonObjects.put(beanName, (singletonObject != null ? singletonObject : NULL_OBJECT));
			this.registeredSingletons.add(beanName);
		}
	}

	public Object getSingleton(String beanName) {
		Object singletonObject = this.singletonObjects.get(beanName);
		return (singletonObject != NULL_OBJECT ? singletonObject : null);
	}

	public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
		Assert.notNull(beanName, "'beanName' 不能为空");
		synchronized (this.singletonObjects) {
			Object singletonObject = this.singletonObjects.get(beanName);
			if (singletonObject == null) {
				if (log.isDebugEnabled()) {
					log.debug("创建共享的单例Bean:'" + beanName + "'");
				}
				singletonObject = singletonFactory.getObject();
				addSingleton(beanName, singletonObject);
			}
			return (singletonObject != NULL_OBJECT ? singletonObject : null);
		}
	}

	public boolean containsSingleton(String beanName) {
		return (this.singletonObjects.containsKey(beanName));
	}

	protected final Object getSingletonObjectsMap() {
		return this.singletonObjects;
	}

}