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org.glassfish.jersey.process.internal.Stage Maven / Gradle / Ivy

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2012 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * http://glassfish.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
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 */
package org.glassfish.jersey.process.internal;

import com.google.common.base.Function;

/**
 * Data processing stage that can be used to create dynamic data processing chains.
 * 

 * An stage is a stateless data processing unit that returns a
 * {@link Continuation processing continuation}.
 * 
 *
 * @param  processed data type.
 * @author Marek Potociar (marek.potociar at oracle.com)
 */
public interface Stage {

    /**
     * Data processing stage continuation.
     * 

     * A continuation of a processing stage is a processing result represented by an
     * ({@link #hasNext() optional}) stage that should be invoked {@link #next() next}
     * and the processed data {@link #result() result}.
     * 
     *
     * @param  processed data type.
     */
    public static final class Continuation {
        private final DATA result;
        private final Stage next;

        /**
         * Create a new continuation instance.
         *
         * @param result processed data.
         * @param next   next processing stage.
         */
        Continuation(final DATA result, final Stage next) {
            this.result = result;
            this.next = next;
        }

        /**
         * Create a continuation from the processed data result and the stage
         * to be invoked next.
         *
         * @param  processed data type.
         * @param result data processing result.
         * @param next   stage to be invoked next.
         * @return a continuation with the supplied stage to be invoked
         *         {@link Stage.Continuation#next() next} in the processing chain
         *         and the supplied processing result.
         */
        public static  Continuation of(final DATA result, Stage next) {
            return new Continuation(result, next);
        }

        /**
         * Create a terminal continuation from the processed data result.
         *
         * @param  processed data type.
         * @param result data processing result.
         * @return terminal continuation with no {@link Stage.Continuation#next() next}
         *         stage in the processing chain and the supplied processing result.
         */
        public static  Continuation of(final DATA result) {
            return new Continuation(result, null);
        }

        /**
         * Get the data processing result.
         *
         * @return data processing result.
         */
        public DATA result() {
            return result;
        }

        /**
         * Get the stage to be invoked next or {@code null} if no next stage is
         * {@link #hasNext() present}.
         *
         * @return the stage to be invoked next or {@code null} if not present.
         */
        public Stage next() {
            return next;
        }

        /**
         * Check if there is a next stage present in the continuation.
         * 

         * The absence of a next stage in the continuation indicates that the data processing
         * reached a terminal stage and the {@link #result() result} of the continuation represents
         * the final result of the whole processing chain.
         * 
         *
         * @return {@code true} if there is a next stage present in the continuation,
         *         {@code false} otherwise.
         */
        public boolean hasNext() {
            return next != null;
        }
    }

    /**
     * Linear stage chain builder.
     *
     * @param  processed data type.
     */
    public static interface Builder {

        /**
         * Add a transformation function as a next stage to the stage chain.
         * 

         * The order of the {@code to(...)} method invocations matches the order
         * of the stage execution at runtime.
         * 
         *
         * @param transformation a transformation function to be added as a next
         *                       stage to the stage chain.
         * @return updated builder instance.
         */
        public Builder to(Function transformation);

        /**
         * Add a new {@link ChainableStage chainable stage} as a next stage to the
         * stage chain.
         * 

         * The order of the {@code to(...)} method invocations matches the order
         * of the stage execution at runtime.
         * A subsequent call to a {@code to(...)} method  will automatically invoke the
         * {@link ChainableStage#setDefaultNext(Stage)} method on the chainable
         * stage.
         * 
         *
         * @param stage a chainable stage to be added as a next
         *                 stage to the stage chain.
         * @return updated builder instance.
         */
        public Builder to(ChainableStage stage);

        /**
         * Build a stage chain.
         *
         * @return built acceptor chain.
         */
        public Stage build();

        /**
         * Add a terminal stage to the stage chain and build the chain.
         *
         * @param terminal last stage to be added to the stage chain.
         * @return built stage chain.
         */
        public Stage build(Stage terminal);
    }

    /**
     * Performs a data processing task and returns the processed data together with
     * a {@link Continuation processing continuation}.
     *
     * @param data data to be transformed.
     * @return a processing continuation.
     */
    public Continuation apply(DATA data);
}