Browse Source
- Introduce abstract base class for Servlet 3.1 and Undertow support - Simplify Undertow supportpull/1111/head
Arjen Poutsma
10 years ago
5 changed files with 480 additions and 534 deletions
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/* |
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* Copyright 2002-2016 the original author or authors. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package org.springframework.http.server.reactive; |
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import java.util.Objects; |
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import java.util.concurrent.atomic.AtomicLong; |
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import org.reactivestreams.Publisher; |
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import org.reactivestreams.Subscriber; |
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import org.reactivestreams.Subscription; |
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import reactor.core.util.BackpressureUtils; |
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import org.springframework.core.io.buffer.DataBuffer; |
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import org.springframework.util.Assert; |
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/** |
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* Abstract base class for {@code Publisher} implementations that bridge between |
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* event-listener APIs and Reactive Streams. Specifically, base class for the Servlet 3.1 |
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* and Undertow support. |
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* |
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* @author Arjen Poutsma |
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* @see ServletServerHttpRequest |
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* @see UndertowHttpHandlerAdapter |
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*/ |
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abstract class AbstractResponseBodyPublisher implements Publisher<DataBuffer> { |
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private ResponseBodySubscription subscription; |
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private volatile boolean stalled; |
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@Override |
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public void subscribe(Subscriber<? super DataBuffer> subscriber) { |
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Objects.requireNonNull(subscriber); |
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Assert.state(this.subscription == null, "Only a single subscriber allowed"); |
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this.subscription = new ResponseBodySubscription(subscriber); |
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subscriber.onSubscribe(this.subscription); |
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} |
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/** |
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* Publishes the given signal to the subscriber. |
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* @param dataBuffer the signal to publish |
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* @see Subscriber#onNext(Object) |
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*/ |
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protected final void publishOnNext(DataBuffer dataBuffer) { |
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Assert.state(this.subscription != null); |
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this.subscription.publishOnNext(dataBuffer); |
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} |
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/** |
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* Publishes the given error to the subscriber. |
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* @param t the error to publish |
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* @see Subscriber#onError(Throwable) |
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*/ |
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protected final void publishOnError(Throwable t) { |
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if (this.subscription != null) { |
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this.subscription.publishOnError(t); |
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} |
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} |
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/** |
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* Publishes the complete signal to the subscriber. |
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* @see Subscriber#onComplete() |
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*/ |
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protected final void publishOnComplete() { |
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if (this.subscription != null) { |
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this.subscription.publishOnComplete(); |
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} |
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} |
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/** |
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* Returns true if the {@code Subscriber} associated with this {@code Publisher} has |
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* cancelled its {@code Subscription}. |
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* @return {@code true} if a subscriber has been registered and its subscription has |
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* been cancelled; {@code false} otherwise |
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* @see ResponseBodySubscription#isCancelled() |
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* @see Subscription#cancel() |
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*/ |
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protected final boolean isSubscriptionCancelled() { |
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return (this.subscription != null && this.subscription.isCancelled()); |
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} |
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/** |
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* Checks the subscription for demand, and marks this publisher as "stalled" if there |
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* is none. The next time the subscriber {@linkplain Subscription#request(long) |
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* requests} more events, the {@link #noLongerStalled()} method is called. |
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* @return {@code true} if there is demand; {@code false} otherwise |
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*/ |
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protected final boolean checkSubscriptionForDemand() { |
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if (this.subscription == null || !this.subscription.hasDemand()) { |
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this.stalled = true; |
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return false; |
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} |
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else { |
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return true; |
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} |
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} |
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/** |
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* Abstract template method called when this publisher is no longer "stalled". Used in |
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* sub-classes to resume reading from the request. |
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*/ |
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protected abstract void noLongerStalled(); |
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private final class ResponseBodySubscription implements Subscription { |
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private final Subscriber<? super DataBuffer> subscriber; |
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private final AtomicLong demand = new AtomicLong(); |
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private boolean cancelled; |
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public ResponseBodySubscription(Subscriber<? super DataBuffer> subscriber) { |
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Assert.notNull(subscriber, "'subscriber' must not be null"); |
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this.subscriber = subscriber; |
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} |
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@Override |
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public final void cancel() { |
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this.cancelled = true; |
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} |
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/** |
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* Indicates whether this subscription has been cancelled. |
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* @see #cancel() |
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*/ |
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protected final boolean isCancelled() { |
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return this.cancelled; |
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} |
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@Override |
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public final void request(long n) { |
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if (!isCancelled() && BackpressureUtils.checkRequest(n, this.subscriber)) { |
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long demand = BackpressureUtils.addAndGet(this.demand, n); |
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if (stalled && demand > 0) { |
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stalled = false; |
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noLongerStalled(); |
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} |
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} |
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} |
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/** |
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* Indicates whether this subscription has demand. |
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* @see #request(long) |
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*/ |
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protected final boolean hasDemand() { |
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return this.demand.get() > 0; |
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} |
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/** |
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* Publishes the given signal to the subscriber wrapped by this subscription, if |
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* it has not been cancelled. If there is {@linkplain #hasDemand() no demand} for |
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* the signal, an exception will be thrown. |
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* @param dataBuffer the signal to publish |
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* @see Subscriber#onNext(Object) |
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*/ |
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protected final void publishOnNext(DataBuffer dataBuffer) { |
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if (!isCancelled()) { |
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if (hasDemand()) { |
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BackpressureUtils.getAndSub(this.demand, 1L); |
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this.subscriber.onNext(dataBuffer); |
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} |
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else { |
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throw new IllegalStateException("No demand for: " + dataBuffer); |
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} |
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} |
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} |
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/** |
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* Publishes the given error to the subscriber wrapped by this subscription, if it |
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* has not been cancelled. |
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* @param t the error to publish |
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* @see Subscriber#onError(Throwable) |
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*/ |
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protected final void publishOnError(Throwable t) { |
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if (!isCancelled()) { |
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this.subscriber.onError(t); |
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} |
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} |
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/** |
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* Publishes the complete signal to the subscriber wrapped by this subscription, |
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* if it has not been cancelled. |
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* @see Subscriber#onComplete() |
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*/ |
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protected final void publishOnComplete() { |
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if (!isCancelled()) { |
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this.subscriber.onComplete(); |
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} |
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} |
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} |
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} |
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