| 24 |
|
* specification. (<b>Preliminary release note:</b> This spec is |
| 25 |
|
* not yet finalized, so minor details could change.) |
| 26 |
|
* |
| 27 |
< |
* <p><b>Preliminary release note:</b> This class may later include |
| 28 |
< |
* methods supporting periodic events and/or async IO. |
| 27 |
> |
* <p><b>Examples.</b> A {@link Publisher} usually defines its own |
| 28 |
> |
* {@link Subscription} implementation; constructing one in method |
| 29 |
> |
* {@code subscribe} and issuing it to the calling {@link |
| 30 |
> |
* Subscriber}. It publishes items to the subscriber asynchronously, |
| 31 |
> |
* normally using an {@link Executor}. For example, here is a very |
| 32 |
> |
* simple publisher that only issues (when requested) a single {@code |
| 33 |
> |
* TRUE} item to each subscriber, then completes. Because each |
| 34 |
> |
* subscriber receives only the same single item, this class does not |
| 35 |
> |
* need the buffering and ordering control required in most |
| 36 |
> |
* implementations. |
| 37 |
> |
* |
| 38 |
> |
* <pre> {@code |
| 39 |
> |
* class OneShotPublisher implements Publisher<Boolean> { |
| 40 |
> |
* final Executor executor = Executors.newSingleThreadExecutor(); |
| 41 |
> |
* public void subscribe(Subscriber<? super Boolean> subscriber) { |
| 42 |
> |
* subscriber.onSubscribe(new OneShotSubscription(subscriber)); |
| 43 |
> |
* } |
| 44 |
> |
* static class OneShotSubscription implements Subscription { |
| 45 |
> |
* final Subscriber<? super Boolean> subscriber; |
| 46 |
> |
* final Executor executor; |
| 47 |
> |
* boolean completed; |
| 48 |
> |
* OneShotSubscription(Subscriber<? super Boolean> subscriber, |
| 49 |
> |
* Executor executor) { |
| 50 |
> |
* this.subscriber = subscriber; |
| 51 |
> |
* this.executor = executor; |
| 52 |
> |
* } |
| 53 |
> |
* public synchronized void request(long n) { |
| 54 |
> |
* if (n > 0 && !completed) { |
| 55 |
> |
* completed = true; |
| 56 |
> |
* executor.execute(() -> { |
| 57 |
> |
* subscriber.onNext(Boolean.TRUE); |
| 58 |
> |
* subscriber.onComplete(); |
| 59 |
> |
* }); |
| 60 |
> |
* } |
| 61 |
> |
* else if (n < 0) { |
| 62 |
> |
* completed = true; |
| 63 |
> |
* subscriber.onError(new IllegalArgumentException()); |
| 64 |
> |
} |
| 65 |
> |
* } |
| 66 |
> |
* public synchronized void cancel() { completed = true; } |
| 67 |
> |
* } |
| 68 |
> |
* }}</pre> |
| 69 |
> |
* |
| 70 |
> |
* <p> A {@link Subscriber} arranges that items be requested and |
| 71 |
> |
* processed. Items (invocations of {@link Subscriber#onNext}) are |
| 72 |
> |
* not issued unless requested, but multiple items may be requested. |
| 73 |
> |
* Many Subscriber implementations can arrange this in the style of |
| 74 |
> |
* the following example, where a buffer size of 1 single-steps, and |
| 75 |
> |
* larger sizes usually allow for more efficient overlapped processing |
| 76 |
> |
* with less communication; for example with a value of 64, this keeps |
| 77 |
> |
* total outstanding requests between 32 and 64. (See also {@link |
| 78 |
> |
* #consume(long, Publisher, Consumer)} that automates a common case.) |
| 79 |
> |
* |
| 80 |
> |
* <pre> {@code |
| 81 |
> |
* class SampleSubscriber<T> implements Subscriber<T> { |
| 82 |
> |
* final Consumer<? super T> consumer; |
| 83 |
> |
* Subscription subscription; |
| 84 |
> |
* final long bufferSize; |
| 85 |
> |
* long count; |
| 86 |
> |
* SampleSubscriber(long bufferSize, Consumer<? super T> consumer) { |
| 87 |
> |
* this.bufferSize = bufferSize; |
| 88 |
> |
* this.consumer = consumer; |
| 89 |
> |
* } |
| 90 |
> |
* public void onSubscribe(Subscription subscription) { |
| 91 |
> |
* (this.subscription = subscription).request(bufferSize); |
| 92 |
> |
* count = bufferSize - bufferSize / 2; // re-request when half consumed |
| 93 |
> |
* } |
| 94 |
> |
* public void onNext(T item) { |
| 95 |
> |
* if (--count <= 0) |
| 96 |
> |
* subscription.request(count = bufferSize - bufferSize / 2); |
| 97 |
> |
* consumer.accept(item); |
| 98 |
> |
* } |
| 99 |
> |
* public void onError(Throwable ex) { ex.printStackTrace(); } |
| 100 |
> |
* public void onComplete() {} |
| 101 |
> |
* }}</pre> |
| 102 |
|
* |
| 103 |
|
* @author Doug Lea |
| 104 |
|
* @since 1.9 |
| 146 |
|
* invoked sequentially by each Subscription, so are not required |
| 147 |
|
* to be thread-safe unless subscribing to multiple publishers. |
| 148 |
|
* |
| 76 |
– |
* <p>Items (invocations of {@link #onNext}) are not issued unless |
| 77 |
– |
* requested, but multiple items may be requested. Many |
| 78 |
– |
* Subscriber implementations can arrange this in the style of the |
| 79 |
– |
* following example, where a request size of 1 single-steps, and |
| 80 |
– |
* larger sizes (for example 64) usually allow for more efficient |
| 81 |
– |
* overlapped processing. (See also {@link #consume(long, Publisher, |
| 82 |
– |
* Consumer)} that automates a common case.) |
| 83 |
– |
* |
| 84 |
– |
* <pre> {@code |
| 85 |
– |
* class SampleSubscriber<T> implements Subscriber<T> { |
| 86 |
– |
* final Consumer<? super T> consumer; |
| 87 |
– |
* Subscription subscription; |
| 88 |
– |
* final long requestSize; |
| 89 |
– |
* long count; |
| 90 |
– |
* SampleSubscriber(long requestSize, Consumer<? super T> consumer) { |
| 91 |
– |
* this.requestSize = requestSize; |
| 92 |
– |
* this.consumer = consumer; |
| 93 |
– |
* } |
| 94 |
– |
* public void onSubscribe(Subscription subscription) { |
| 95 |
– |
* count = requestSize / 2; // re-request when half consumed |
| 96 |
– |
* (this.subscription = subscription).request(requestSize); |
| 97 |
– |
* } |
| 98 |
– |
* public void onNext(T item) { |
| 99 |
– |
* if (--count <= 0) |
| 100 |
– |
* subscription.request(count = requestSize); |
| 101 |
– |
* consumer.accept(item); |
| 102 |
– |
* } |
| 103 |
– |
* public void onError(Throwable ex) { ex.printStackTrace(); } |
| 104 |
– |
* public void onComplete() {} |
| 105 |
– |
* }}</pre> |
| 106 |
– |
* |
| 149 |
|
* @param <T> the subscribed item type |
| 150 |
|
*/ |
| 151 |
|
public static interface Subscriber<T> { |
| 231 |
|
|
| 232 |
|
// Support for static methods |
| 233 |
|
|
| 234 |
< |
static final long DEFAULT_REQUEST_SIZE = 64L; |
| 234 |
> |
static final long DEFAULT_BUFFER_SIZE = 64L; |
| 235 |
|
|
| 236 |
|
abstract static class CompletableSubscriber<T,U> implements Subscriber<T>, |
| 237 |
|
Consumer<T> { |
| 238 |
|
final CompletableFuture<U> status; |
| 239 |
|
Subscription subscription; |
| 240 |
< |
final long requestSize; |
| 240 |
> |
long requestSize; |
| 241 |
|
long count; |
| 242 |
< |
CompletableSubscriber(long requestSize, |
| 201 |
< |
CompletableFuture<U> status) { |
| 242 |
> |
CompletableSubscriber(long bufferSize, CompletableFuture<U> status) { |
| 243 |
|
this.status = status; |
| 244 |
< |
this.requestSize = requestSize; |
| 204 |
< |
this.count = requestSize >>> 1; |
| 244 |
> |
this.requestSize = bufferSize; |
| 245 |
|
} |
| 246 |
|
public final void onSubscribe(Subscription subscription) { |
| 247 |
|
(this.subscription = subscription).request(requestSize); |
| 248 |
< |
status.exceptionally(ex -> { subscription.cancel(); return null;}); |
| 248 |
> |
count = requestSize -= (requestSize >>> 1); |
| 249 |
|
} |
| 250 |
|
public final void onError(Throwable ex) { |
| 211 |
– |
if (ex == null) |
| 212 |
– |
ex = new IllegalStateException("null onError argument"); |
| 251 |
|
status.completeExceptionally(ex); |
| 252 |
|
} |
| 253 |
|
public void onNext(T item) { |
| 254 |
< |
Subscription s = subscription; |
| 255 |
< |
if (s == null) |
| 256 |
< |
status.completeExceptionally( |
| 257 |
< |
new IllegalStateException("onNext without subscription")); |
| 258 |
< |
else { |
| 259 |
< |
try { |
| 222 |
< |
if (--count <= 0) |
| 223 |
< |
s.request(count = requestSize); |
| 224 |
< |
accept(item); |
| 225 |
< |
} catch (Throwable ex) { |
| 226 |
< |
status.completeExceptionally(ex); |
| 227 |
< |
} |
| 254 |
> |
try { |
| 255 |
> |
if (--count <= 0) |
| 256 |
> |
subscription.request(count = requestSize); |
| 257 |
> |
accept(item); |
| 258 |
> |
} catch (Throwable ex) { |
| 259 |
> |
status.completeExceptionally(ex); |
| 260 |
|
} |
| 261 |
|
} |
| 262 |
|
} |
| 263 |
|
|
| 264 |
|
static final class ConsumeSubscriber<T> extends CompletableSubscriber<T,Void> { |
| 265 |
|
final Consumer<? super T> consumer; |
| 266 |
< |
ConsumeSubscriber(long requestSize, |
| 266 |
> |
ConsumeSubscriber(long bufferSize, |
| 267 |
|
CompletableFuture<Void> status, |
| 268 |
|
Consumer<? super T> consumer) { |
| 269 |
< |
super(requestSize, status); |
| 269 |
> |
super(bufferSize, status); |
| 270 |
|
this.consumer = consumer; |
| 271 |
|
} |
| 272 |
|
public void accept(T item) { consumer.accept(item); } |
| 276 |
|
/** |
| 277 |
|
* Creates and subscribes a Subscriber that consumes all items |
| 278 |
|
* from the given publisher using the given Consumer function, and |
| 279 |
< |
* using the given requestSize for buffering. Returns a |
| 279 |
> |
* using the given bufferSize for buffering. Returns a |
| 280 |
|
* CompletableFuture that is completed normally when the publisher |
| 281 |
|
* signals onComplete, or completed exceptionally upon any error, |
| 282 |
|
* including an exception thrown by the Consumer (in which case |
| 283 |
|
* the subscription is cancelled if not already terminated). |
| 284 |
|
* |
| 285 |
|
* @param <T> the published item type |
| 286 |
< |
* @param requestSize the request size for subscriptions |
| 286 |
> |
* @param bufferSize the request size for subscriptions |
| 287 |
|
* @param publisher the publisher |
| 288 |
|
* @param consumer the function applied to each onNext item |
| 289 |
|
* @return a CompletableFuture that is completed normally |
| 290 |
|
* when the publisher signals onComplete, and exceptionally |
| 291 |
|
* upon any error |
| 292 |
|
* @throws NullPointerException if publisher or consumer are null |
| 293 |
< |
* @throws IllegalArgumentException if requestSize not positive |
| 293 |
> |
* @throws IllegalArgumentException if bufferSize not positive |
| 294 |
|
*/ |
| 295 |
|
public static <T> CompletableFuture<Void> consume( |
| 296 |
< |
long requestSize, Publisher<T> publisher, Consumer<? super T> consumer) { |
| 297 |
< |
if (requestSize <= 0L) |
| 298 |
< |
throw new IllegalArgumentException("requestSize must be positive"); |
| 296 |
> |
long bufferSize, Publisher<T> publisher, Consumer<? super T> consumer) { |
| 297 |
> |
if (bufferSize <= 0L) |
| 298 |
> |
throw new IllegalArgumentException("bufferSize must be positive"); |
| 299 |
|
if (publisher == null || consumer == null) |
| 300 |
|
throw new NullPointerException(); |
| 301 |
|
CompletableFuture<Void> status = new CompletableFuture<>(); |
| 302 |
|
publisher.subscribe(new ConsumeSubscriber<T>( |
| 303 |
< |
requestSize, status, consumer)); |
| 303 |
> |
bufferSize, status, consumer)); |
| 304 |
|
return status; |
| 305 |
|
} |
| 306 |
|
|
| 307 |
|
/** |
| 308 |
|
* Equivalent to {@link #consume(long, Publisher, Consumer)} |
| 309 |
< |
* with a request size of 64. |
| 309 |
> |
* with a buffer size of 64. |
| 310 |
|
* |
| 311 |
|
* @param <T> the published item type |
| 312 |
|
* @param publisher the publisher |
| 318 |
|
*/ |
| 319 |
|
public static <T> CompletableFuture<Void> consume( |
| 320 |
|
Publisher<T> publisher, Consumer<? super T> consumer) { |
| 321 |
< |
return consume(DEFAULT_REQUEST_SIZE, publisher, consumer); |
| 321 |
> |
return consume(DEFAULT_BUFFER_SIZE, publisher, consumer); |
| 322 |
|
} |
| 323 |
|
|
| 324 |
|
/** |
| 328 |
|
static final class StreamSubscriber<T,R> extends CompletableSubscriber<T,R> { |
| 329 |
|
final Function<? super Stream<T>, ? extends R> fn; |
| 330 |
|
final ArrayList<T> items; |
| 331 |
< |
StreamSubscriber(long requestSize, |
| 331 |
> |
StreamSubscriber(long bufferSize, |
| 332 |
|
CompletableFuture<R> status, |
| 333 |
|
Function<? super Stream<T>, ? extends R> fn) { |
| 334 |
< |
super(requestSize, status); |
| 334 |
> |
super(bufferSize, status); |
| 335 |
|
this.fn = fn; |
| 336 |
|
this.items = new ArrayList<T>(); |
| 337 |
|
} |
| 341 |
|
|
| 342 |
|
/** |
| 343 |
|
* Creates and subscribes a Subscriber that applies the given |
| 344 |
< |
* stream operation to items, and uses the given requestSize for |
| 344 |
> |
* stream operation to items, and uses the given bufferSize for |
| 345 |
|
* buffering. Returns a CompletableFuture that is completed |
| 346 |
|
* normally with the result of this function when the publisher |
| 347 |
|
* signals onComplete, or is completed exceptionally upon any |
| 353 |
|
* |
| 354 |
|
* @param <T> the published item type |
| 355 |
|
* @param <R> the result type of the stream function |
| 356 |
< |
* @param requestSize the request size for subscriptions |
| 356 |
> |
* @param bufferSize the request size for subscriptions |
| 357 |
|
* @param publisher the publisher |
| 358 |
|
* @param streamFunction the operation on elements |
| 359 |
|
* @return a CompletableFuture that is completed normally with the |
| 360 |
|
* result of the given function as result when the publisher signals |
| 361 |
|
* onComplete, and exceptionally upon any error |
| 362 |
|
* @throws NullPointerException if publisher or function are null |
| 363 |
< |
* @throws IllegalArgumentException if requestSize not positive |
| 363 |
> |
* @throws IllegalArgumentException if bufferSize not positive |
| 364 |
|
*/ |
| 365 |
|
public static <T,R> CompletableFuture<R> stream( |
| 366 |
< |
long requestSize, Publisher<T> publisher, |
| 366 |
> |
long bufferSize, Publisher<T> publisher, |
| 367 |
|
Function<? super Stream<T>, ? extends R> streamFunction) { |
| 368 |
< |
if (requestSize <= 0L) |
| 369 |
< |
throw new IllegalArgumentException("requestSize must be positive"); |
| 368 |
> |
if (bufferSize <= 0L) |
| 369 |
> |
throw new IllegalArgumentException("bufferSize must be positive"); |
| 370 |
|
if (publisher == null || streamFunction == null) |
| 371 |
|
throw new NullPointerException(); |
| 372 |
|
CompletableFuture<R> status = new CompletableFuture<>(); |
| 373 |
|
publisher.subscribe(new StreamSubscriber<T,R>( |
| 374 |
< |
requestSize, status, streamFunction)); |
| 374 |
> |
bufferSize, status, streamFunction)); |
| 375 |
|
return status; |
| 376 |
|
} |
| 377 |
|
|
| 378 |
|
/** |
| 379 |
|
* Equivalent to {@link #stream(long, Publisher, Function)} |
| 380 |
< |
* with a request size of 64. |
| 380 |
> |
* with a buffer size of 64. |
| 381 |
|
* |
| 382 |
|
* @param <T> the published item type |
| 383 |
|
* @param <R> the result type of the stream function |
| 391 |
|
public static <T,R> CompletableFuture<R> stream( |
| 392 |
|
Publisher<T> publisher, |
| 393 |
|
Function<? super Stream<T>,? extends R> streamFunction) { |
| 394 |
< |
return stream(DEFAULT_REQUEST_SIZE, publisher, streamFunction); |
| 394 |
> |
return stream(DEFAULT_BUFFER_SIZE, publisher, streamFunction); |
| 395 |
|
} |
| 396 |
+ |
|
| 397 |
|
} |
