setfactorybean.java

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/*
 * Copyright 2002-2005 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.beans.factory.config;

import java.util.Set;

import org.springframework.beans.BeanUtils;
import org.springframework.core.CollectionFactory;

/**
 * Simple factory for shared Set instances. Allows for central setup
 * of Sets via the "set" element in XML bean definitions.
 *
 * @author Juergen Hoeller
 * @since 21.01.2003
 * @see ListFactoryBean
 * @see MapFactoryBean
 */
public class SetFactoryBean extends AbstractFactoryBean {

	private Set sourceSet;

	private Class targetSetClass;


	/**
	 * Set the source Set, typically populated via XML "set" elements.
	 */
	public void setSourceSet(Set sourceSet) {
		this.sourceSet = sourceSet;
	}

	/**
	 * Set the class to use for the target Set. Can be populated with a fully
	 * qualified class name when defined in a Spring application context.
	 * <p>Default is a linked HashSet, keeping the registration order.
	 * If no linked Set implementation is available, a plain HashSet will
	 * be used as fallback (not keeping the registration order).
	 * @see org.springframework.core.CollectionFactory#createLinkedSetIfPossible
	 */
	public void setTargetSetClass(Class targetSetClass) {
		if (targetSetClass == null) {
			throw new IllegalArgumentException("targetSetClass must not be null");
		}
		if (!Set.class.isAssignableFrom(targetSetClass)) {
			throw new IllegalArgumentException("targetSetClass must implement [java.util.Set]");
		}
		this.targetSetClass = targetSetClass;
	}


	public Class getObjectType() {
		return Set.class;
	}

	protected Object createInstance() {
		if (this.sourceSet == null) {
			throw new IllegalArgumentException("sourceSet is required");
		}
		Set result = null;
		if (this.targetSetClass != null) {
			result = (Set) BeanUtils.instantiateClass(this.targetSetClass);
		}
		else {
			result = CollectionFactory.createLinkedSetIfPossible(this.sourceSet.size());
		}
		result.addAll(this.sourceSet);
		return result;
	}

}