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example for some sink operators #25468

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Examples for takeLast, last and lastOption operators
This commit is contained in:
mohammad mehdi 2018-10-25 17:10:36 +03:30 • committed by Johan Andrén
parent 91b0c387be
commit ba996f8c5f
6 changed files with 124 additions and 19 deletions
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6
akka-docs/src/main/paradox/stream/operators/Sink/last.md
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@ -26,4 +26,10 @@ completes. If the stream completes with no elements the @scala[`Future`] @java[`
@@@
## Example
Scala
: @@snip [LastSinkSpec.scala](/akka-stream-tests/src/test/scala/akka/stream/scaladsl/LastSinkSpec.scala) { #last-operator-example }
Java
: @@snip [SinkDocExamples.java](/akka-docs/src/test/java/jdocs/stream/operators/SinkDocExamples.java) { #last-operator-example }

7
akka-docs/src/main/paradox/stream/operators/Sink/lastOption.md
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@ -27,3 +27,10 @@ completed with @scala[`None`] @java[an empty `Optional`].
@@@
## Example
Scala
: @@snip [LastSinkSpec.scala](/akka-stream-tests/src/test/scala/akka/stream/scaladsl/LastSinkSpec.scala) { #lastOption-operator-example }
Java
: @@snip [SinkDocExamples.java](/akka-docs/src/test/java/jdocs/stream/operators/SinkDocExamples.java) { #lastOption-operator-example }

6
akka-docs/src/main/paradox/stream/operators/Sink/takeLast.md
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@ -28,4 +28,10 @@ If there is a failure signaled in the stream the @scala[`Future`] @java[`Complet
@@@
## Example
Scala
: @@snip [TakeLastSinkSpec.scala](/akka-stream-tests/src/test/scala/akka/stream/scaladsl/TakeLastSinkSpec.scala) { #takeLast-operator-example }
Java
: @@snip [SinkDocExamples.java](/akka-docs/src/test/java/jdocs/stream/operators/SinkDocExamples.java) { #takeLast-operator-example }

61
akka-docs/src/test/java/jdocs/stream/operators/SinkDocExamples.java
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@ -6,30 +6,75 @@ package jdocs.stream.operators;
import akka.NotUsed;
import akka.actor.ActorSystem;
import akka.stream.ActorMaterializer;
import akka.stream.Materializer;
import akka.stream.javadsl.Sink;
import akka.stream.javadsl.Source;
import java.util.Arrays;
//#takeLast-operator-example
import akka.japi.Pair;
//#takeLast-operator-example
import java.util.*;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public class SinkDocExamples {
private final static ActorSystem system = ActorSystem.create("SourceFromExample");
private final static Materializer materializer = ActorMaterializer.create(system);
static void reduceExample() throws InterruptedException, ExecutionException, TimeoutException {
final ActorSystem system = ActorSystem.create("SourceFromExample");
final Materializer materializer = ActorMaterializer.create(system);
//#reduce-operator-example
Source<Integer, NotUsed> ints = Source.from(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
CompletionStage<Integer> sum = ints.runWith(Sink.reduce((a, b) -> a + b), materializer);
int result = sum.toCompletableFuture().get(3, TimeUnit.SECONDS);
System.out.println(result);
sum.thenAccept(System.out::println);
// 55
//#reduce-operator-example
}
}
static void takeLastExample() throws InterruptedException, ExecutionException, TimeoutException {
//#takeLast-operator-example
// pair of (Name, GPA)
List<Pair> sortedStudents = Arrays.asList(new Pair<>("Benita", 2.1), new Pair<>("Adrian", 3.1),
new Pair<>("Alexis", 4), new Pair<>("Kendra", 4.2), new Pair<>("Jerrie", 4.3), new Pair<>("Alison", 4.7));
Source<Pair, NotUsed> studentSource = Source.from(sortedStudents);
CompletionStage<List<Pair>> topThree = studentSource.runWith(Sink.takeLast(3), materializer);
topThree.thenAccept(result -> {
System.out.println("#### Top students ####");
for (int i = result.size() - 1; i >= 0; i--) {
Pair<String, Double> s = result.get(i);
System.out.println("Name: " + s.first() + ", " + "GPA: " + s.second());
}
});
/*
#### Top students ####
Name: Alison, GPA: 4.7
Name: Jerrie, GPA: 4.3
Name: Kendra, GPA: 4.2
*/
//#takeLast-operator-example
}
static void lastExample() throws InterruptedException, ExecutionException, TimeoutException {
//#last-operator-example
Source<Integer, NotUsed> source = Source.from(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
CompletionStage<Integer> result = source.runWith(Sink.last(), materializer);
result.thenAccept(System.out::println);
// 10
//#last-operator-example
}
static void lastOptionExample() throws InterruptedException, ExecutionException, TimeoutException {
//#lastOption-operator-example
Source<Integer, NotUsed> source = Source.empty();
CompletionStage<Optional<Integer>> result = source.runWith(Sink.lastOption(), materializer);
result.thenAccept(System.out::println);
// Optional.empty
//#lastOption-operator-example
}
}

33
akka-stream-tests/src/test/scala/akka/stream/scaladsl/LastSinkSpec.scala
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@ -4,25 +4,30 @@
package akka.stream.scaladsl
import scala.concurrent.Await
import scala.concurrent.duration._
import akka.stream.ActorMaterializer
import akka.stream.ActorMaterializerSettings
import akka.stream.{ ActorMaterializer, ActorMaterializerSettings }
import akka.stream.testkit._
import akka.stream.testkit.Utils._
import akka.stream.testkit.scaladsl.StreamTestKit._
import scala.concurrent.duration._
import scala.concurrent.{ Await, Future }
class LastSinkSpec extends StreamSpec with ScriptedTest {
val settings = ActorMaterializerSettings(system)
implicit val materializer = ActorMaterializer(settings)
implicit val materializer: ActorMaterializer = ActorMaterializer(settings)
implicit val ec = system.dispatcher
"A Flow with Sink.last" must {
"yield the last value" in assertAllStagesStopped {
Await.result(Source(1 to 42).map(identity).runWith(Sink.last), 1.second) should be(42)
"yield the last value" in {
//#last-operator-example
val source = Source(1 to 10)
val result: Future[Int] = source.runWith(Sink.last)
result.map(println)
// 10
//#last-operator-example
result.futureValue shouldEqual 10
}
"yield the first error" in assertAllStagesStopped {
@ -52,8 +57,14 @@ class LastSinkSpec extends StreamSpec with ScriptedTest {
} should be theSameInstanceAs (ex)
}
"yield None for empty stream" in assertAllStagesStopped {
Await.result(Source.empty[Int].runWith(Sink.lastOption), 1.second) should be(None)
"yield None for empty stream" in {
//#lastOption-operator-example
val source = Source.empty[Int]
val result: Future[Option[Int]] = source.runWith(Sink.lastOption)
result.map(println)
// None
//#lastOption-operator-example
result.futureValue shouldEqual None
}
}

30
akka-stream-tests/src/test/scala/akka/stream/scaladsl/TakeLastSinkSpec.scala
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@ -25,6 +25,36 @@ class TakeLastSinkSpec extends StreamSpec {
result should be(Seq(4, 5, 6))
}
"return top three student based on GPA correctly" in {
implicit val ex = system.dispatcher
//#takeLast-operator-example
case class Student(name: String, gpa: Double)
val students = List(Student("Alison", 4.7), Student("Adrian", 3.1), Student("Alexis", 4),
Student("Benita", 2.1), Student("Kendra", 4.2), Student("Jerrie", 4.3)).sortBy(_.gpa)
val sourceOfStudents = Source(students)
val result: Future[Seq[Student]] = sourceOfStudents.runWith(Sink.takeLast(3))
result.foreach { topThree ⇒
println("#### Top students ####")
topThree.reverse foreach { s ⇒
println(s"Name: ${s.name}, GPA: ${s.gpa}")
}
}
/*
#### Top students ####
Name: Alison, GPA: 4.7
Name: Jerrie, GPA: 4.3
Name: Kendra, GPA: 4.2
*/
//#takeLast-operator-example
result.futureValue shouldEqual students.takeRight(3)
}
"return the number of elements taken when the stream completes" in {
val input = 1 to 4
val future: Future[immutable.Seq[Int]] = Source(input).runWith(Sink.takeLast(5))