Add support for configurable Executor implementations (#281)

Author: jhalterman

src/main/java/net/jodah/failsafe/FailsafeExecutor.java

@@ -345,7 +345,7 @@ public FailsafeExecutor<R> with(ScheduledExecutorService executor) {
    *
    * @throws NullPointerException if {@code executor} is null
    */
-  public FailsafeExecutor<R> with(ExecutorService executor) {
+  public FailsafeExecutor<R> with(Executor executor) {
     this.scheduler = Scheduler.of(executor);
     return this;
   }

src/main/java/net/jodah/failsafe/internal/util/DelegatingExecutorService.java

@@ -0,0 +1,44 @@
+package net.jodah.failsafe.internal.util;
+
+import java.util.List;
+import java.util.concurrent.*;
+
+/**
+ * Delegates executions to an underlying {@link Executor}.
+ */
+public class DelegatingExecutorService extends AbstractExecutorService {
+  private final Executor executor;
+
+  public DelegatingExecutorService(Executor executor) {
+    this.executor = executor;
+  }
+
+  @Override
+  public void shutdown() {
+  }
+
+  @Override
+  public List<Runnable> shutdownNow() {
+    return null;
+  }
+
+  @Override
+  public boolean isShutdown() {
+    return false;
+  }
+
+  @Override
+  public boolean isTerminated() {
+    return false;
+  }
+
+  @Override
+  public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
+    return false;
+  }
+
+  @Override
+  public void execute(Runnable command) {
+    executor.execute(command);
+  }
+}

src/main/java/net/jodah/failsafe/util/concurrent/Scheduler.java

@@ -16,6 +16,7 @@
 package net.jodah.failsafe.util.concurrent;
 
 import net.jodah.failsafe.internal.util.Assert;
+import net.jodah.failsafe.internal.util.DelegatingExecutorService;
 import net.jodah.failsafe.internal.util.DelegatingScheduler;
 
 import java.util.concurrent.*;
@@ -53,7 +54,11 @@ static Scheduler of(final ScheduledExecutorService executor) {
    *
    * @throws NullPointerException if {@code executor} is null
    */
-  static Scheduler of(final ExecutorService executor) {
-    return new DelegatingScheduler(Assert.notNull(executor, "executor"));
+  static Scheduler of(final Executor executor) {
+    Assert.notNull(executor, "executor");
+    ExecutorService executorService = executor instanceof ExecutorService ?
+      (ExecutorService) executor :
+      new DelegatingExecutorService(executor);
+    return new DelegatingScheduler(executorService);
   }
 }

src/test/java/net/jodah/failsafe/AsyncExecutionTest.java

@@ -15,6 +15,8 @@
  */
 package net.jodah.failsafe;
 
+import net.jodah.failsafe.Testing.Stats;
+import net.jodah.failsafe.Testing.SyncExecutor;
 import net.jodah.failsafe.util.concurrent.Scheduler;
 import org.testng.annotations.BeforeMethod;
 import org.testng.annotations.Test;
@@ -24,6 +26,8 @@
 import java.util.concurrent.Callable;
 import java.util.concurrent.TimeUnit;
 
+import static net.jodah.failsafe.Testing.testAsyncFailure;
+import static net.jodah.failsafe.Testing.withStats;
 import static org.mockito.Mockito.*;
 import static org.testng.Assert.*;
 
@@ -185,7 +189,7 @@ public void testRetryOn() {
     // Given rpRetry on IllegalArgumentException
     exec = new AsyncExecution(scheduler, future,
       executorFor(new RetryPolicy<>().handle(IllegalArgumentException.class)));
-    exec.inject(Functions.getPromise(ctx-> null, exec), true);
+    exec.inject(Functions.getPromise(ctx -> null, exec), true);
 
     // When / Then
     assertTrue(exec.retryOn(new IllegalArgumentException()));
@@ -250,6 +254,20 @@ public void testCompleteOrRetry() {
     verify(future).completeResult(ExecutionResult.NONE);
   }
 
+  public void testExecutor() {
+    Stats rpStats = new Stats();
+    RetryPolicy<Object> rp = withStats(new RetryPolicy<>(), rpStats, false);
+
+    testAsyncFailure(Failsafe.with(rp).with(new SyncExecutor()), () -> {
+      throw new IllegalStateException();
+    }, e -> {
+      assertEquals(e.getAttemptCount(), 3);
+      assertEquals(e.getExecutionCount(), 3);
+      assertEquals(rpStats.failedAttemptCount, 3);
+      assertEquals(rpStats.retryCount, 2);
+    }, IllegalStateException.class);
+  }
+
   @SuppressWarnings("unchecked")
   private void resetMocks() {
     reset(scheduler);