wicket-ioc/src/main/java/org/apache/wicket/proxy/IProxyTargetLocator.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.wicket.proxy;

import org.apache.wicket.proxy.cglib.CglibProxyFactory;
import org.apache.wicket.util.io.IClusterable;

/**
 * Represents a service locator for lazy init proxies. When the first method invocation occurs on
 * the lazy init proxy this locator will be used to retrieve the proxy target object that will
 * receive the method invocation.
 * <p>
 * Generally implementations should be small when serialized because the main purpose of lazy init
 * proxies is to be stored in session when the wicket pages are serialized, and when deserialized to
 * be able to lookup the dependency again. The smaller the implementation of IProxyTargetLocator the
 * less the drain on session size.
 * <p>
 * A small implementation may use a static lookup to retrieve the target object.
 * <p>
 * Example:
 * 
 * <pre>
 * class UserServiceLocator implements IProxyTargetLocator
 * {
 * 	Object locateProxyObject()
 * 	{
 * 		MyApplication app = (MyApplication)Application.get();
 * 		return app.getUserService();
 * 	}
 * }
 * </pre>
 * 
 * @see CglibProxyFactory#createProxy(Class, IProxyTargetLocator)
 * 
 * @author Igor Vaynberg (ivaynberg)
 * 
 */
public interface IProxyTargetLocator extends IClusterable
{
	/**
	 * Returns the object that will be used as target object for a lazy init proxy.
	 * 
	 * @return retrieved object
	 */
	Object locateProxyTarget();
}