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/*
 * Licensed to the University Corporation for Advanced Internet Development,
 * Inc. (UCAID) under one or more contributor license agreements.  See the
 * NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The UCAID 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 net.shibboleth.utilities.java.support.service;

import javax.annotation.Nonnull;

/**
 * Any component that wants to be reloaded via the Service interface and Spring implements this interface.
 * 
 * The idea is that the attribute resolver will be
 * 
 * public class AttributeResolver extends AbstractServiceableComponent<AttributeResolver> implements
 *  AttributeResolver, ServiceableComponent<ServiceableComponent>.
 *  
 *  AbstractServiceableComponent will do all the work around reload and synchronization.
 *  
 * @param  The underlying type of the component.
 */
public interface ServiceableComponent {

    /**
     * Extract the component that does the actual work.  Callers MUST have the ServiceableComponent
     * pinned at this stage.
     *
     * @return the component.
     */
    @Nonnull T getComponent();
    
    /**
     * This function takes a lock on the component which guarantees that it will not be disposed until the unpin call
     * is made.
     * 
     * This method is typically only used during initialization of the component.
     * 
     * Every call to {@link #pinComponent()} must be matched by a call to {@link #unpinComponent()}.
     */
    void pinComponent();

    /**
     * This undoes the work that is done by {@link #pinComponent()}.
     */
    void unpinComponent();
    

    /**
     * This call will wait for all transient operations to complete and then
     * calls dispose on the components.
     *
     * Implementations should avoid calling this with locks held.
     */
    void unloadComponent();
}