Merge pull request #18 from spotify/krka/completionstage

Add CompletableFuturesExtra.toListenableFuture(CompletionStage)
spotify · Nov 11, 2015 · 0939ee9 · 0939ee9
2 parents da64237 + 802111d
commit 0939ee9
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Showing 3 changed files with 25 additions and 3 deletions.
diff --git a/src/main/java/com/spotify/futures/CompletableFuturesExtra.java b/src/main/java/com/spotify/futures/CompletableFuturesExtra.java
@@ -18,6 +18,7 @@
 import com.google.common.util.concurrent.ListenableFuture;
 
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
 
 public class CompletableFuturesExtra {
 
@@ -50,6 +51,18 @@ public static <V> CompletableFuture<V> toCompletableFuture(
    */
   public static <V> ListenableFuture<V> toListenableFuture(
       CompletableFuture<V> future) {
+    return toListenableFuture((CompletionStage<V>) future);
+  }
+
+  /**
+   * Wrap a {@link CompletionStage} in a {@link ListenableFuture}. The returned future will
+   * complete with the same result or failure as the original future.
+   *
+   * @param future The {@link CompletionStage} to wrap in a {@link ListenableFuture}.
+   * @return A {@link ListenableFuture} that completes when the original future completes.
+   */
+  public static <V> ListenableFuture<V> toListenableFuture(
+      CompletionStage<V> future) {
     if (future instanceof ListenableToCompletableFutureWrapper) {
       return ((ListenableToCompletableFutureWrapper<V>) future).unwrap();
     }

diff --git a/src/main/java/com/spotify/futures/CompletableToListenableFutureWrapper.java b/src/main/java/com/spotify/futures/CompletableToListenableFutureWrapper.java
@@ -19,21 +19,22 @@
 import com.google.common.util.concurrent.ListenableFuture;
 
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
 import java.util.function.BiConsumer;
 
 class CompletableToListenableFutureWrapper<V>
     extends AbstractFuture<V>
     implements ListenableFuture<V>, BiConsumer<V, Throwable> {
 
-  private final CompletableFuture<V> future;
+  private final CompletionStage<V> future;
 
-  CompletableToListenableFutureWrapper(final CompletableFuture<V> future) {
+  CompletableToListenableFutureWrapper(final CompletionStage<V> future) {
     this.future = future;
     future.whenComplete(this);
   }
 
   public CompletableFuture<V> unwrap() {
-    return future;
+    return future.toCompletableFuture();
   }
 
   @Override

diff --git a/src/test/java/com/spotify/futures/jdk8/CompletableFuturesExtraTest.java b/src/test/java/com/spotify/futures/jdk8/CompletableFuturesExtraTest.java
@@ -14,6 +14,7 @@
 import org.mockito.runners.MockitoJUnitRunner;
 
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
 import java.util.concurrent.ExecutionException;
 import java.util.function.BiConsumer;
 
@@ -49,6 +50,13 @@ public void testToCompletableFutureUnwrap() {
     assertThat(unwrapped, is(sameInstance(listenable)));
   }
 
+  @Test
+  public void testToCompletableFutureUnwrapWithStage() {
+    final CompletionStage<String> wrapped = toCompletableFuture(listenable);
+    final ListenableFuture<String> unwrapped = toListenableFuture(wrapped);
+    assertThat(unwrapped, is(sameInstance(listenable)));
+  }
+
   @Test
   public void testToCompletableFutureSuccess() throws ExecutionException, InterruptedException {
     @SuppressWarnings("unchecked") final BiConsumer<String, Throwable> consumer = mock(BiConsumer.class);