/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* You can obtain a copy of the license at
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* trunk/opends/resource/legal-notices/OpenDS.LICENSE
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* or https://OpenDS.dev.java.net/OpenDS.LICENSE.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at
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* trunk/opends/resource/legal-notices/OpenDS.LICENSE. If applicable,
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* add the following below this CDDL HEADER, with the fields enclosed
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* by brackets "[]" replaced with your own identifying information:
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* Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*
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*
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* Copyright 2009 Sun Microsystems, Inc.
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*/
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package com.sun.opends.sdk.util;
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import java.util.concurrent.TimeUnit;
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import java.util.concurrent.TimeoutException;
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import org.opends.sdk.ErrorResultException;
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import org.opends.sdk.FutureResult;
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import org.opends.sdk.ResultHandler;
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/**
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* An implementation of the {@code FutureResult} interface which transforms the
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* result of an asynchronous operation from one type to another. The
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* implementation ensures that the transformed is computed only once.
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*
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* @param <M>
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* The type of the inner result.
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* @param <N>
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* The type of the outer result.
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*/
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public abstract class FutureResultTransformer<M, N> implements FutureResult<N>,
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ResultHandler<M>
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{
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private final ResultHandler<? super N> handler;
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private volatile FutureResult<? extends M> future = null;
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// These do not need to be volatile since the future acts as a memory
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// barrier.
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private N transformedResult = null;
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private ErrorResultException transformedErrorResult = null;
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/**
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* Creates a new result transformer which will transform the results of an
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* inner asynchronous request.
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*
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* @param handler
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* The outer result handler.
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*/
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protected FutureResultTransformer(final ResultHandler<? super N> handler)
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{
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this.handler = handler;
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}
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/**
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* {@inheritDoc}
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*/
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public final boolean cancel(final boolean mayInterruptIfRunning)
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{
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return future.cancel(mayInterruptIfRunning);
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}
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/**
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* {@inheritDoc}
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*/
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public final N get() throws ErrorResultException, InterruptedException
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{
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future.get();
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// The handlers are guaranteed to have been invoked at this point.
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return get0();
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}
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/**
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* {@inheritDoc}
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*/
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public final N get(final long timeout, final TimeUnit unit)
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throws ErrorResultException, TimeoutException, InterruptedException
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{
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future.get(timeout, unit);
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// The handlers are guaranteed to have been invoked at this point.
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return get0();
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}
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/**
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* {@inheritDoc}
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*/
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public final int getRequestID()
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{
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return future.getRequestID();
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}
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/**
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* {@inheritDoc}
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*/
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public final void handleErrorResult(final ErrorResultException error)
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{
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transformedErrorResult = transformErrorResult(error);
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if (handler != null)
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{
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handler.handleErrorResult(transformedErrorResult);
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}
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}
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/**
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* {@inheritDoc}
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*/
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public final void handleResult(final M result)
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{
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try
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{
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transformedResult = transformResult(result);
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if (handler != null)
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{
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handler.handleResult(transformedResult);
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}
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}
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catch (final ErrorResultException e)
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{
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transformedErrorResult = e;
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if (handler != null)
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{
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handler.handleErrorResult(transformedErrorResult);
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}
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}
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}
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/**
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* {@inheritDoc}
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*/
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public final boolean isCancelled()
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{
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return future.isCancelled();
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}
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/**
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* {@inheritDoc}
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*/
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public final boolean isDone()
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{
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return future.isDone();
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}
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/**
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* Sets the inner future for this result transformer. This must be done before
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* this future is published.
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*
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* @param future
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* The inner future.
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*/
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public final void setFutureResult(final FutureResult<? extends M> future)
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{
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this.future = future;
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}
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/**
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* Transforms the inner error result to an outer error result. The default
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* implementation is to return the inner error result.
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*
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* @param errorResult
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* The inner error result.
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* @return The outer error result.
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*/
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protected ErrorResultException transformErrorResult(
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final ErrorResultException errorResult)
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{
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return errorResult;
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}
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/**
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* Transforms the inner result to an outer result, possibly throwing an
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* {@code ErrorResultException} if the transformation fails for some reason.
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*
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* @param result
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* The inner result.
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* @return The outer result.
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* @throws ErrorResultException
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* If the transformation fails for some reason.
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*/
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protected abstract N transformResult(M result) throws ErrorResultException;
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private N get0() throws ErrorResultException
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{
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if (transformedErrorResult != null)
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{
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throw transformedErrorResult;
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}
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else
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{
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return transformedResult;
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}
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}
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}
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