/*
 * Copyright 2002-2012 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;

/**
 * Thread-backed {@link Scope} implementation.
 *
 * <p><strong>Note</strong> that the {@code SimpleThreadScope} <em>does not clean up any objects</em> associated
 * with it. As such, it's typically preferable to use the {@link org.springframework.web.context.request.RequestScope}
 * in Web environments.
 *
 * <p>For a implementation of a thread-based {@code Scope} with support for destruction callbacks, refer to <a
 * href="http://www.springbyexample.org/twiki/bin/view/Example/CustomThreadScopeModule">this module</a>.
 *
 * <p>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<Map<String, Object>> threadScope =
			new NamedThreadLocal<Map<String, Object>>("SimpleThreadScope") {
				@Override
				protected Map<String, Object> initialValue() {
					return new HashMap<String, Object>();
				}
			};

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

	public Object remove(String name) {
		Map<String, Object> scope = threadScope.get();
		return scope.remove(name);
	}

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

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

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

}
