1 /*

     2  * Copyright (c) 2019, 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.

     8  *

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

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

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

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

    13  * accompanied this code).

    14  *

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

    16  * 2 along with this work; if not, write to the Free Software Foundation,

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

    18  *

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

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

    21  * questions.

    22  */

    23 

    24 package org.reactivestreams;

    25 

    26 /**

    27  * Will receive call to {@link #onSubscribe(Subscription)} once after passing an instance of {@link Subscriber} to {@link Publisher#subscribe(Subscriber)}.

    28  * <p>

    29  * No further notifications will be received until {@link Subscription#request(long)} is called.

    30  * <p>

    31  * After signaling demand:

    32  * <ul>

    33  * <li>One or more invocations of {@link #onNext(Object)} up to the maximum number defined by {@link Subscription#request(long)}</li>

    34  * <li>Single invocation of {@link #onError(Throwable)} or {@link Subscriber#onComplete()} which signals a terminal state after which no further events will be sent.

    35  * </ul>

    36  * <p>

    37  * Demand can be signaled via {@link Subscription#request(long)} whenever the {@link Subscriber} instance is capable of handling more.

    38  *

    39  * @param <T> the type of element signaled.

    40  */

    41 public interface Subscriber<T> {

    42     /**

    43      * Invoked after calling {@link Publisher#subscribe(Subscriber)}.

    44      * <p>

    45      * No data will start flowing until {@link Subscription#request(long)} is invoked.

    46      * <p>

    47      * It is the responsibility of this {@link Subscriber} instance to call {@link Subscription#request(long)} whenever more data is wanted.

    48      * <p>

    49      * The {@link Publisher} will send notifications only in response to {@link Subscription#request(long)}.

    50      *

    51      * @param s

    52      *            {@link Subscription} that allows requesting data via {@link Subscription#request(long)}

    53      */

    54     public void onSubscribe(Subscription s);

    55 

    56     /**

    57      * Data notification sent by the {@link Publisher} in response to requests to {@link Subscription#request(long)}.

    58      *

    59      * @param t the element signaled

    60      */

    61     public void onNext(T t);

    62 

    63     /**

    64      * Failed terminal state.

    65      * <p>

    66      * No further events will be sent even if {@link Subscription#request(long)} is invoked again.

    67      *

    68      * @param t the throwable signaled

    69      */

    70     public void onError(Throwable t);

    71 

    72     /**

    73      * Successful terminal state.

    74      * <p>

    75      * No further events will be sent even if {@link Subscription#request(long)} is invoked again.

    76      */

    77     public void onComplete();

    78 }