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/*
 * Copyright 2002-2015 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.springframework.context.support;

import java.util.HashMap;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.config.Scope;
import org.springframework.core.NamedThreadLocal;

/**
 * A simple thread-backed {@link Scope} implementation.
 *
 * NOTE: This thread scope is not registered by default in common contexts.
 * Instead, you need to explicitly assign it to a scope key in your setup, either through
 * {@link org.springframework.beans.factory.config.ConfigurableBeanFactory#registerScope}
 * or through a {@link org.springframework.beans.factory.config.CustomScopeConfigurer} bean.
 *
 * 
{@code SimpleThreadScope} does not clean up any objects associated with it.
 * As such, it is typically preferable to use
 * {@link org.springframework.web.context.request.RequestScope RequestScope}
 * in web environments.
 *
 * 
For an implementation of a thread-based {@code Scope} with support for
 * destruction callbacks, refer to the
 * 
*  Spring by Example Custom Thread Scope Module.
 *
 * Thanks to Eugene Kuleshov for submitting the original prototype for a thread scope!
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @since 3.0
 * @see org.springframework.web.context.request.RequestScope
 */
public class SimpleThreadScope implements Scope {

	private static final Log logger = LogFactory.getLog(SimpleThreadScope.class);

	private final ThreadLocal> threadScope =
			new NamedThreadLocal>("SimpleThreadScope") {
				@Override
				protected Map initialValue() {
					return new HashMap();
				}
			};


	@Override
	public Object get(String name, ObjectFactory objectFactory) {
		Map scope = this.threadScope.get();
		Object object = scope.get(name);
		if (object == null) {
			object = objectFactory.getObject();
			scope.put(name, object);
		}
		return object;
	}

	@Override
	public Object remove(String name) {
		Map scope = this.threadScope.get();
		return scope.remove(name);
	}

	@Override
	public void registerDestructionCallback(String name, Runnable callback) {
		logger.warn("SimpleThreadScope does not support destruction callbacks. " +
				"Consider using RequestScope in a web environment.");
	}

	@Override
	public Object resolveContextualObject(String key) {
		return null;
	}

	@Override
	public String getConversationId() {
		return Thread.currentThread().getName();
	}

}