/*
 * Copyright 2002-2018 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.web.servlet.view.tiles3;

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

import org.apache.tiles.TilesException;
import org.apache.tiles.preparer.PreparerException;
import org.apache.tiles.preparer.ViewPreparer;
import org.apache.tiles.preparer.factory.NoSuchPreparerException;

import org.springframework.util.ClassUtils;
import org.springframework.web.context.WebApplicationContext;

Tiles PreparerFactory implementation that expects preparer class names and builds preparer instances for those, creating them through the Spring ApplicationContext in order to apply Spring container callbacks and configured Spring BeanPostProcessors. 
Author:
Juergen Hoeller
See Also:
SpringBeanPreparerFactory
Since:
3.2/**
 * Tiles {@link org.apache.tiles.preparer.PreparerFactory} implementation
 * that expects preparer class names and builds preparer instances for those,
 * creating them through the Spring ApplicationContext in order to apply
 * Spring container callbacks and configured Spring BeanPostProcessors.
 *
 * @author Juergen Hoeller
 * @since 3.2
 * @see SpringBeanPreparerFactory
 */
public class SimpleSpringPreparerFactory extends AbstractSpringPreparerFactory {

	
Cache of shared ViewPreparer instances: bean name -> bean instance. /** Cache of shared ViewPreparer instances: bean name -> bean instance. */
	private final Map<String, ViewPreparer> sharedPreparers = new ConcurrentHashMap<>(16);


	@Override
	protected ViewPreparer getPreparer(String name, WebApplicationContext context) throws TilesException {
		// Quick check on the concurrent map first, with minimal locking.
		ViewPreparer preparer = this.sharedPreparers.get(name);
		if (preparer == null) {
			synchronized (this.sharedPreparers) {
				preparer = this.sharedPreparers.get(name);
				if (preparer == null) {
					try {
						Class<?> beanClass = ClassUtils.forName(name, context.getClassLoader());
						if (!ViewPreparer.class.isAssignableFrom(beanClass)) {
							throw new PreparerException(
									"Invalid preparer class [" + name + "]: does not implement ViewPreparer interface");
						}
						preparer = (ViewPreparer) context.getAutowireCapableBeanFactory().createBean(beanClass);
						this.sharedPreparers.put(name, preparer);
					}
					catch (ClassNotFoundException ex) {
						throw new NoSuchPreparerException("Preparer class [" + name + "] not found", ex);
					}
				}
			}
		}
		return preparer;
	}

}