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/*
 * Copyright (c) 2000, 2023, Oracle and/or its affiliates.
 *
 * Licensed under the Universal Permissive License v 1.0 as shown at
 * https://oss.oracle.com/licenses/upl.
 */

package com.oracle.coherence.client;

import io.grpc.stub.StreamObserver;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;

/**
 * A simple {@link io.grpc.stub.StreamObserver} adapter class that completes a {@link CompletableFuture} when the
 * observer is completed.
 * 

* This observer uses the value passed to its {@link #onNext(Object)} method to complete the {@link CompletableFuture}. *

* This observer should only be used in cases where a single result is expected. If more that one call is made to {@link * #onNext(Object)} then future will be completed with an exception. * * @param The type of objects received in this stream. * * @author Jonathan Knight 2020.09.21 * @since 20.06 */ public class SingleValueStreamObserver implements StreamObserver { // ----- constructors --------------------------------------------------- /** * Create a SingleValueStreamObserver. */ public SingleValueStreamObserver() { } // ----- StreamObserver methods ----------------------------------------- @Override public void onNext(T value) { if (m_cNext++ == 0) { m_oResult = value; } else { f_future.completeExceptionally(new IllegalStateException("More than one result received.")); } } @Override public void onError(Throwable t) { f_future.completeExceptionally(t); } @Override public void onCompleted() { f_future.complete(m_oResult); } // ----- accessors ------------------------------------------------------ /** * Obtain the {@link CompletableFuture} that will be completed when * the {@link io.grpc.stub.StreamObserver} completes. * * @return The CompletableFuture */ public CompletionStage completionStage() { return f_future; } // ----- data members --------------------------------------------------- private int m_cNext; private T m_oResult; private final CompletableFuture f_future = new CompletableFuture<>(); }





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