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Java 9 Flow bridge: add Subscriber converters #399

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Merged
merged 2 commits into from
Oct 14, 2017
Merged

Java 9 Flow bridge: add Subscriber converters #399

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376b159
Java 9 Flow bridge: add Subscriber converters
akarnokd Oct 12, 2017
18459a4
Fix return type javadoc
akarnokd Oct 12, 2017
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28 changes: 27 additions & 1 deletion flow-bridge/src/main/java/org/reactivestreams/ReactiveStreamsFlowBridge.java
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Original file line number Diff line number Diff line change
Expand Up @@ -110,7 +110,33 @@ public static <T, U> Flow.Processor<T, U> toFlow(
}
return new FlowToReactiveProcessor<T, U>(reactiveStreamsProcessor);
}


/**
* Converts a Reactive Streams Subscriber into a Flow Subscriber.
* @param <T> the input and output value type
* @param reactiveStreamsSubscriber the Reactive Streams Subscriber instance to convert
* @return the equivalent Flow Subscriber
*/
public static <T> Flow.Subscriber<T> toFlowSubscriber(org.reactivestreams.Subscriber<T> reactiveStreamsSubscriber) {
if (reactiveStreamsSubscriber == null) {
throw new NullPointerException("reactiveStreamsSubscriber");
}
return new FlowToReactiveSubscriber<T>(reactiveStreamsSubscriber);
}

/**
* Converts a Flow Subscriber into a Reactive Streams Subscriber.
* @param <T> the input and output value type
* @param flowSubscriber the Flow Subscriber instance to convert
* @return the equivalent Flow Subscriber
*/
public static <T> org.reactivestreams.Subscriber<T> toReactiveStreamsSubscriber(Flow.Subscriber<T> flowSubscriber) {
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Hm, I wonder actually; now it's onconsistent since most methods are toFlow and to ReactiveStreams and this one adds the specific type name - should we align them to the same style?

The overloaded version works fine too I think, just toX everywhere, but I have no strong preference WDYT?

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I think there might be an ambiguity problem with toFlow(Processor) when trying to convert a Processor, requiring the user to cast. For consistency though, a postfix could be added to the other methods.

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If the intended usage is to import static then I think it's fine to harmonize on "toReactiveStreamsX" and "toFlowX". Thoughts?

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Yeah good catch that a processor would be ambigious then... I'd avoid having 2 methods to do the same, so I guess for consistency we should do the long names everywhere.

if (flowSubscriber == null) {
throw new NullPointerException("flowSubscriber");
}
return new ReactiveToFlowSubscriber<T>(flowSubscriber);
}

/**
* Wraps a Reactive Streams Subscription and converts the calls to a Flow Subscription.
*/
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65 changes: 65 additions & 0 deletions flow-bridge/src/test/java/org/reactivestreams/ReactiveStreamsFlowBridgeTest.java
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Expand Up @@ -11,6 +11,7 @@

package org.reactivestreams;

import org.testng.Assert;
import org.testng.annotations.Test;

import java.io.IOException;
Expand Down Expand Up @@ -110,4 +111,68 @@ public void execute(Runnable command) {

tc.assertFailure(IOException.class, 1, 2, 3, 4, 5);
}

@Test
public void reactiveStreamsToFlowSubscriber() {
TestEitherConsumer<Integer> tc = new TestEitherConsumer<Integer>();

Flow.Subscriber<Integer> fs = ReactiveStreamsFlowBridge.toFlowSubscriber(tc);

final Object[] state = { null, null };

fs.onSubscribe(new Flow.Subscription() {
@Override
public void request(long n) {
state[0] = n;
}

@Override
public void cancel() {
state[1] = true;
}
});

Assert.assertEquals(state[0], Long.MAX_VALUE);

fs.onNext(1);
fs.onNext(2);
fs.onNext(3);
fs.onComplete();

tc.assertResult(1, 2, 3);

Assert.assertNull(state[1]);
}

@Test
public void flowToReactiveStreamsSubscriber() {
TestEitherConsumer<Integer> tc = new TestEitherConsumer<Integer>();

org.reactivestreams.Subscriber<Integer> fs = ReactiveStreamsFlowBridge.toReactiveStreamsSubscriber(tc);

final Object[] state = { null, null };

fs.onSubscribe(new org.reactivestreams.Subscription() {
@Override
public void request(long n) {
state[0] = n;
}

@Override
public void cancel() {
state[1] = true;
}
});

Assert.assertEquals(state[0], Long.MAX_VALUE);

fs.onNext(1);
fs.onNext(2);
fs.onNext(3);
fs.onComplete();

tc.assertResult(1, 2, 3);

Assert.assertNull(state[1]);
}
}