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/*-
* ============LICENSE_START=======================================================
* SDC
* ================================================================================
* Copyright (C) 2017 AT&T Intellectual Property. All rights reserved.
* ================================================================================
* 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.
* ============LICENSE_END=========================================================
*/
package org.openecomp.core.factory.api;
import org.openecomp.core.factory.impl.AbstractFactoryBase;
/**
* This class provides generic implementation of an abstract factory. Components exposed as Java interfaces should have their own concrete factories
* derived from the given class. This assures code alignment and consistency across all Service Management components. The class actually uses
* singleton pattern to instantiate and reuse just one instance of a factory. Therefore, each factory implementation has to be <i>thread-safe</i>. In
* a general case, the hierarchy of factory objects for an Java interface <tt>IUknown</tt> may look as follows:
* <pre>
* AbstractFactory<IUnknown>
* ^
* |
* Application code ----> ConcreteFactory
* ^
* |
* +---------+---------+
* | |
* BaselineFactoryImpl CustomFactoryImpl
* </pre>
* Where the classes responsibility is: <ul> <li>Abstract factory - common logic to retrieve the implementation class name from a central
* repository.</li> <li>Concrete factory - abstract class that only exposes to application layer the type specific API such as: <ul> <li><tt>public
* static ConcreteFactory getInstance()</tt></li> </ul> <li>Baseline factory - out of the box implementation of concrete factory (that can be replaced
* by a custom one depending on customer needs) which actually implements method: <ul> <li><tt>public IUnknown createInterface()</tt></li>
* </ul> </ul> The normal concrete factory class may look like:
* <pre>
* public abstract class ConcreteFactory extends AbstractFactory<IUnknown> {
* static {
* registerFactory(ConcreteFactory.class, BaselineFactoryImpl.class);
* }
* public static ConcreteFactory getInstance() {
* return AbstractFactory.<IUnknown, ConcreteFactory.class>getInstance(ConcreteFactory.class);
* }
* }
* </pre>
*
* @param <I> Java interface type created by the factory.
*/
public abstract class AbstractFactory<I> extends AbstractFactoryBase {
/**
* Returns the interface implementor instance.
* <b>Note</b>: It's up to the concrete factory to decide on the actual
* implementation of the returned interface. Therefore, the call can get the same instance per each call in case of singleton implementation or
* new instance otherwise. However, the API consumer may not assume anything regarding the underlying logic and has always go through the factory
* to obtain the reference.
*
* @return Implementor of the exposed Java interface.
*/
public abstract I createInterface();
} // End of class
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