/*
 * 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.aop.scope;

import java.lang.reflect.Modifier;

import org.springframework.aop.framework.AopInfrastructureBean;
import org.springframework.aop.framework.ProxyConfig;
import org.springframework.aop.framework.ProxyFactory;
import org.springframework.aop.support.DelegatingIntroductionInterceptor;
import org.springframework.aop.target.SimpleBeanTargetSource;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.FactoryBeanNotInitializedException;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

Convenient proxy factory bean for scoped objects.
Proxies created using this factory bean are thread-safe singletons
and may be injected into shared objects, with transparent scoping behavior.
Proxies returned by this class implement the ScopedObject interface. This presently allows for removing the corresponding object from the scope, seamlessly creating a new instance in the scope on next access. 
Please note that the proxies created by this factory are
class-based proxies by default. This can be customized
through switching the "proxyTargetClass" property to "false".
Author:
Rod Johnson, Juergen Hoeller
See Also:
ProxyConfig.setProxyTargetClass
Since:
2.0/**
 * Convenient proxy factory bean for scoped objects.
 *
 * <p>Proxies created using this factory bean are thread-safe singletons
 * and may be injected into shared objects, with transparent scoping behavior.
 *
 * <p>Proxies returned by this class implement the {@link ScopedObject} interface.
 * This presently allows for removing the corresponding object from the scope,
 * seamlessly creating a new instance in the scope on next access.
 *
 * <p>Please note that the proxies created by this factory are
 * <i>class-based</i> proxies by default. This can be customized
 * through switching the "proxyTargetClass" property to "false".
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @since 2.0
 * @see #setProxyTargetClass
 */
@SuppressWarnings("serial")
public class ScopedProxyFactoryBean extends ProxyConfig
		implements FactoryBean<Object>, BeanFactoryAware, AopInfrastructureBean {

	
The TargetSource that manages scoping. /** The TargetSource that manages scoping. */
	private final SimpleBeanTargetSource scopedTargetSource = new SimpleBeanTargetSource();

	
The name of the target bean. /** The name of the target bean. */
	@Nullable
	private String targetBeanName;

	
The cached singleton proxy. /** The cached singleton proxy. */
	@Nullable
	private Object proxy;


	
Create a new ScopedProxyFactoryBean instance.
/**
	 * Create a new ScopedProxyFactoryBean instance.
	 */
	public ScopedProxyFactoryBean() {
		setProxyTargetClass(true);
	}


	
Set the name of the bean that is to be scoped.
/**
	 * Set the name of the bean that is to be scoped.
	 */
	public void setTargetBeanName(String targetBeanName) {
		this.targetBeanName = targetBeanName;
		this.scopedTargetSource.setTargetBeanName(targetBeanName);
	}

	@Override
	public void setBeanFactory(BeanFactory beanFactory) {
		if (!(beanFactory instanceof ConfigurableBeanFactory)) {
			throw new IllegalStateException("Not running in a ConfigurableBeanFactory: " + beanFactory);
		}
		ConfigurableBeanFactory cbf = (ConfigurableBeanFactory) beanFactory;

		this.scopedTargetSource.setBeanFactory(beanFactory);

		ProxyFactory pf = new ProxyFactory();
		pf.copyFrom(this);
		pf.setTargetSource(this.scopedTargetSource);

		Assert.notNull(this.targetBeanName, "Property 'targetBeanName' is required");
		Class<?> beanType = beanFactory.getType(this.targetBeanName);
		if (beanType == null) {
			throw new IllegalStateException("Cannot create scoped proxy for bean '" + this.targetBeanName +
					"': Target type could not be determined at the time of proxy creation.");
		}
		if (!isProxyTargetClass() || beanType.isInterface() || Modifier.isPrivate(beanType.getModifiers())) {
			pf.setInterfaces(ClassUtils.getAllInterfacesForClass(beanType, cbf.getBeanClassLoader()));
		}

		// Add an introduction that implements only the methods on ScopedObject.
		ScopedObject scopedObject = new DefaultScopedObject(cbf, this.scopedTargetSource.getTargetBeanName());
		pf.addAdvice(new DelegatingIntroductionInterceptor(scopedObject));

		// Add the AopInfrastructureBean marker to indicate that the scoped proxy
		// itself is not subject to auto-proxying! Only its target bean is.
		pf.addInterface(AopInfrastructureBean.class);

		this.proxy = pf.getProxy(cbf.getBeanClassLoader());
	}


	@Override
	public Object getObject() {
		if (this.proxy == null) {
			throw new FactoryBeanNotInitializedException();
		}
		return this.proxy;
	}

	@Override
	public Class<?> getObjectType() {
		if (this.proxy != null) {
			return this.proxy.getClass();
		}
		return this.scopedTargetSource.getTargetClass();
	}

	@Override
	public boolean isSingleton() {
		return true;
	}

}