1 /*

     2  * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package jdk.internal.net.http.common;

    27 

    28 import java.util.concurrent.CompletableFuture;

    29 import java.util.concurrent.CompletionStage;

    30 import java.util.concurrent.atomic.AtomicLong;

    31 

    32 import static java.util.Objects.requireNonNull;

    33 

    34 /*

    35  * A CompletableFuture which does not allow any obtrusion logic.

    36  * All methods of CompletionStage return instances of this class.

    37  */

    38 public final class MinimalFuture<T> extends CompletableFuture<T> {

    39 

    40     @FunctionalInterface

    41     public interface ExceptionalSupplier<U> {

    42         U get() throws Throwable;

    43     }

    44 

    45     private final static AtomicLong TOKENS = new AtomicLong();

    46     private final long id;

    47 

    48     public static <U> MinimalFuture<U> completedFuture(U value) {

    49         MinimalFuture<U> f = new MinimalFuture<>();

    50         f.complete(value);

    51         return f;

    52     }

    53 

    54     public static <U> CompletableFuture<U> failedFuture(Throwable ex) {

    55         requireNonNull(ex);

    56         MinimalFuture<U> f = new MinimalFuture<>();

    57         f.completeExceptionally(ex);

    58         return f;

    59     }

    60 

    61     public static <U> CompletableFuture<U> supply(ExceptionalSupplier<U> supplier) {

    62         CompletableFuture<U> cf = new MinimalFuture<>();

    63         try {

    64             U value = supplier.get();

    65             cf.complete(value);

    66         } catch (Throwable t) {

    67             cf.completeExceptionally(t);

    68         }

    69         return cf;

    70     }

    71 

    72     public MinimalFuture() {

    73         super();

    74         this.id = TOKENS.incrementAndGet();

    75     }

    76 

    77     @Override

    78     public <U> MinimalFuture<U> newIncompleteFuture() {

    79         return new MinimalFuture<>();

    80     }

    81 

    82     @Override

    83     public void obtrudeValue(T value) {

    84         throw new UnsupportedOperationException();

    85     }

    86 

    87     @Override

    88     public void obtrudeException(Throwable ex) {

    89         throw new UnsupportedOperationException();

    90     }

    91 

    92     @Override

    93     public String toString() {

    94         return super.toString() + " (id=" + id +")";

    95     }

    96 

    97     public static <U> MinimalFuture<U> of(CompletionStage<U> stage) {

    98         MinimalFuture<U> cf = new MinimalFuture<>();

    99         stage.whenComplete((r,t) -> complete(cf, r, t));

   100         return cf;

   101     }

   102 

   103     private static <U> void complete(CompletableFuture<U> cf, U result, Throwable t) {

   104         if (t == null) {

   105             cf.complete(result);

   106         } else {

   107             cf.completeExceptionally(t);

   108         }

   109     }

   110 }