/*
 * Copyright 2002-2017 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.io.IOException;
import java.util.Properties;

import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.core.io.support.PropertiesLoaderSupport;
import org.springframework.lang.Nullable;

Allows for making a properties file from a classpath location available
as Properties instance in a bean factory. Can be used to populate
any bean property of type Properties via a bean reference.
Supports loading from a properties file and/or setting local properties
on this FactoryBean. The created Properties instance will be merged from
loaded and local values. If neither a location nor local properties are set,
an exception will be thrown on initialization.
Can create a singleton or a new object on each request.
Default is a singleton.
Author:
Juergen Hoeller
See Also:
PropertiesLoaderSupport.setLocation
PropertiesLoaderSupport.setProperties
PropertiesLoaderSupport.setLocalOverride
Properties/**
 * Allows for making a properties file from a classpath location available
 * as Properties instance in a bean factory. Can be used to populate
 * any bean property of type Properties via a bean reference.
 *
 * <p>Supports loading from a properties file and/or setting local properties
 * on this FactoryBean. The created Properties instance will be merged from
 * loaded and local values. If neither a location nor local properties are set,
 * an exception will be thrown on initialization.
 *
 * <p>Can create a singleton or a new object on each request.
 * Default is a singleton.
 *
 * @author Juergen Hoeller
 * @see #setLocation
 * @see #setProperties
 * @see #setLocalOverride
 * @see java.util.Properties
 */
public class PropertiesFactoryBean extends PropertiesLoaderSupport
		implements FactoryBean<Properties>, InitializingBean {

	private boolean singleton = true;

	@Nullable
	private Properties singletonInstance;


	
Set whether a shared 'singleton' Properties instance should be
created, or rather a new Properties instance on each request.
Default is "true" (a shared singleton).
/**
	 * Set whether a shared 'singleton' Properties instance should be
	 * created, or rather a new Properties instance on each request.
	 * <p>Default is "true" (a shared singleton).
	 */
	public final void setSingleton(boolean singleton) {
		this.singleton = singleton;
	}

	@Override
	public final boolean isSingleton() {
		return this.singleton;
	}


	@Override
	public final void afterPropertiesSet() throws IOException {
		if (this.singleton) {
			this.singletonInstance = createProperties();
		}
	}

	@Override
	@Nullable
	public final Properties getObject() throws IOException {
		if (this.singleton) {
			return this.singletonInstance;
		}
		else {
			return createProperties();
		}
	}

	@Override
	public Class<Properties> getObjectType() {
		return Properties.class;
	}


	
Template method that subclasses may override to construct the object
returned by this factory. The default implementation returns the
plain merged Properties instance.
Invoked on initialization of this FactoryBean in case of a shared singleton; else, on each getObject() call. 
Throws:
IOException – if an exception occurred during properties loading
See Also:
PropertiesLoaderSupport.mergeProperties()
Returns:
the object returned by this factory/**
	 * Template method that subclasses may override to construct the object
	 * returned by this factory. The default implementation returns the
	 * plain merged Properties instance.
	 * <p>Invoked on initialization of this FactoryBean in case of a
	 * shared singleton; else, on each {@link #getObject()} call.
	 * @return the object returned by this factory
	 * @throws IOException if an exception occurred during properties loading
	 * @see #mergeProperties()
	 */
	protected Properties createProperties() throws IOException {
		return mergeProperties();
	}

}