doc #20466 Java range-directives examples added (#20892)

* #20466 Java range-directives examples added

* #20466 post-review changes

akka-docs/rst/java/code/docs/http/javadsl/server/directives/RangeDirectivesExamplesTest.java

@@ -0,0 +1,88 @@
+/**
+ * Copyright (C) 2016-2016 Lightbend Inc. <http://www.lightbend.com>
+ */
+package docs.http.javadsl.server.directives;
+
+import akka.http.javadsl.model.HttpRequest;
+import akka.http.javadsl.model.Multipart;
+import akka.http.javadsl.model.StatusCodes;
+import akka.http.javadsl.model.headers.ByteRange;
+import akka.http.javadsl.model.headers.ContentRange;
+import akka.http.javadsl.model.headers.Range;
+import akka.http.javadsl.model.headers.RangeUnits;
+import akka.http.javadsl.server.Route;
+import akka.http.javadsl.server.Unmarshaller;
+import akka.http.javadsl.testkit.JUnitRouteTest;
+import akka.http.javadsl.testkit.TestRouteResult;
+import akka.stream.ActorMaterializer;
+import akka.util.ByteString;
+import com.typesafe.config.Config;
+import com.typesafe.config.ConfigFactory;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.TimeUnit;
+
+public class RangeDirectivesExamplesTest extends JUnitRouteTest {
+    @Override
+    public Config additionalConfig() {
+        return ConfigFactory.parseString("akka.http.routing.range-coalescing-threshold=2");
+    }
+
+    @Test
+    public void testWithRangeSupport() {
+        //#withRangeSupport
+        final Route route = withRangeSupport(() -> complete("ABCDEFGH"));
+
+        // test:
+        final String bytes348Range = ContentRange.create(RangeUnits.BYTES,
+                akka.http.javadsl.model.ContentRange.create(3, 4, 8)).value();
+        final akka.http.javadsl.model.ContentRange bytes028Range =
+                akka.http.javadsl.model.ContentRange.create(0, 2, 8);
+        final akka.http.javadsl.model.ContentRange bytes678Range =
+                akka.http.javadsl.model.ContentRange.create(6, 7, 8);
+        final ActorMaterializer materializer = systemResource().materializer();
+
+        testRoute(route).run(HttpRequest.GET("/")
+                .addHeader(Range.create(RangeUnits.BYTES, ByteRange.createSlice(3, 4))))
+                .assertHeaderKindExists("Content-Range")
+                .assertHeaderExists("Content-Range", bytes348Range)
+                .assertStatusCode(StatusCodes.PARTIAL_CONTENT)
+                .assertEntity("DE");
+
+        // we set "akka.http.routing.range-coalescing-threshold = 2"
+        // above to make sure we get two BodyParts
+        final TestRouteResult response = testRoute(route).run(HttpRequest.GET("/")
+                .addHeader(Range.create(RangeUnits.BYTES,
+                        ByteRange.createSlice(0, 1), ByteRange.createSlice(1, 2), ByteRange.createSlice(6, 7))));
+        response.assertHeaderKindNotExists("Content-Range");
+
+        final CompletionStage<List<Multipart.ByteRanges.BodyPart>> completionStage =
+                response.entity(Unmarshaller.entityToMultipartByteRanges()).getParts()
+                        .runFold(new ArrayList<>(), (acc, n) -> {
+                            acc.add(n);
+                            return acc;
+                        }, materializer);
+        try {
+            final List<Multipart.ByteRanges.BodyPart> bodyParts =
+                    completionStage.toCompletableFuture().get(3, TimeUnit.SECONDS);
+            assertResult(2, bodyParts.toArray().length);
+
+            final Multipart.ByteRanges.BodyPart part1 = bodyParts.get(0);
+            assertResult(bytes028Range, part1.getContentRange());
+            assertResult(ByteString.fromString("ABC"),
+                    part1.toStrict(1000, materializer).toCompletableFuture().get().getEntity().getData());
+
+            final Multipart.ByteRanges.BodyPart part2 = bodyParts.get(1);
+            assertResult(bytes678Range, part2.getContentRange());
+            assertResult(ByteString.fromString("GH"),
+                    part2.toStrict(1000, materializer).toCompletableFuture().get().getEntity().getData());
+
+        } catch (Exception e) {
+            // please handle this in production code
+        }
+        //#
+    }
+}

akka-docs/rst/java/http/routing-dsl/directives/range-directives/withRangeSupport.rst

@@ -27,4 +27,5 @@ See also: https://tools.ietf.org/html/rfc7233
 
 Example
 -------
-TODO: Example snippets for JavaDSL are subject to community contributions! Help us complete the docs, read more about it here: `write example snippets for Akka HTTP Java DSL #20466 <https://github.com/akka/akka/issues/20466>`_.
+.. includecode2:: ../../../../code/docs/http/javadsl/server/directives/RangeDirectivesExamplesTest.java
+   :snippet: withRangeSupport