Move MonoToListenableFutureAdapter to spring-core

This was a package private class in spring-messaging since 5.0, and was
recently made public in 5.1. This commit promotes it to spring-core
where it belongs next to all other ListenableFuture support classes.

Follow-up refactoring for SPR-17336

spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/ReactiveReturnValueHandler.java

@@ -21,9 +21,9 @@ import reactor.core.publisher.Mono;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
-import org.springframework.messaging.support.MonoToListenableFutureAdapter;
 import org.springframework.util.Assert;
 import org.springframework.util.concurrent.ListenableFuture;
+import org.springframework.util.concurrent.MonoToListenableFutureAdapter;
 
 /**
  * Support for single-value reactive types (like {@code Mono} or {@code Single})

spring-messaging/src/main/java/org/springframework/messaging/support/MonoToListenableFutureAdapter.java

@@ -1,44 +0,0 @@
-/*
- * Copyright 2002-2018 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.springframework.messaging.support;
-
-import reactor.core.publisher.Mono;
-
-import org.springframework.lang.Nullable;
-
-/**
- * A Mono-to-ListenableFuture adapter where the source and the target from
- * the Promise and the ListenableFuture respectively are of the same type.
- *
- * @author Rossen Stoyanchev
- * @author Stephane Maldini
- * @since 5.0
- * @param <T> the object type
- */
-public class MonoToListenableFutureAdapter<T> extends AbstractMonoToListenableFutureAdapter<T, T> {
-
-	public MonoToListenableFutureAdapter(Mono<T> mono) {
-		super(mono);
-	}
-
-	@Override
-	@Nullable
-	protected T adapt(@Nullable T result) {
-		return result;
-	}
-
-}

spring-messaging/src/main/java/org/springframework/messaging/tcp/reactor/ReactorNettyTcpClient.java

@@ -49,13 +49,13 @@ import reactor.netty.tcp.TcpClient;
 
 import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
-import org.springframework.messaging.support.MonoToListenableFutureAdapter;
 import org.springframework.messaging.tcp.ReconnectStrategy;
 import org.springframework.messaging.tcp.TcpConnection;
 import org.springframework.messaging.tcp.TcpConnectionHandler;
 import org.springframework.messaging.tcp.TcpOperations;
 import org.springframework.util.Assert;
 import org.springframework.util.concurrent.ListenableFuture;
+import org.springframework.util.concurrent.MonoToListenableFutureAdapter;
 import org.springframework.util.concurrent.SettableListenableFuture;
 
 /**

spring-messaging/src/main/java/org/springframework/messaging/tcp/reactor/ReactorNettyTcpConnection.java

@@ -23,9 +23,9 @@ import reactor.netty.NettyInbound;
 import reactor.netty.NettyOutbound;
 
 import org.springframework.messaging.Message;
-import org.springframework.messaging.support.MonoToListenableFutureAdapter;
 import org.springframework.messaging.tcp.TcpConnection;
 import org.springframework.util.concurrent.ListenableFuture;
+import org.springframework.util.concurrent.MonoToListenableFutureAdapter;
 
 /**
  * Reactor Netty based implementation of {@link TcpConnection}.

spring-messaging/src/test/java/org/springframework/messaging/support/MonoToListenableFutureAdapterTests.java

@@ -1,72 +0,0 @@
-/*
- * Copyright 2002-2018 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.messaging.support;
-
-import java.time.Duration;
-import java.util.concurrent.Future;
-import java.util.concurrent.atomic.AtomicReference;
-
-import org.junit.Test;
-import reactor.core.publisher.Mono;
-
-import org.springframework.util.concurrent.ListenableFuture;
-
-import static org.junit.Assert.*;
-
-/**
- * Unit tests for {@link MonoToListenableFutureAdapter}.
- * @author Rossen Stoyanchev
- */
-public class MonoToListenableFutureAdapterTests {
-
-	@Test
-	public void success() {
-		String expected = "one";
-		AtomicReference<Object> actual = new AtomicReference<>();
-		ListenableFuture<String> future = new MonoToListenableFutureAdapter<>(Mono.just(expected));
-		future.addCallback(actual::set, actual::set);
-
-		assertEquals(expected, actual.get());
-	}
-
-	@Test
-	public void failure() {
-		Throwable expected = new IllegalStateException("oops");
-		AtomicReference<Object> actual = new AtomicReference<>();
-		ListenableFuture<String> future = new MonoToListenableFutureAdapter<>(Mono.error(expected));
-		future.addCallback(actual::set, actual::set);
-
-		assertEquals(expected, actual.get());
-	}
-
-	@Test
-	public void cancellation() {
-		Mono<Long> mono = Mono.delay(Duration.ofSeconds(60));
-		Future<Long> future = new MonoToListenableFutureAdapter<>(mono);
-
-		assertTrue(future.cancel(true));
-		assertTrue(future.isCancelled());
-	}
-
-	@Test
-	public void cancellationAfterTerminated() {
-		Future<Void> future = new MonoToListenableFutureAdapter<>(Mono.empty());
-
-		assertFalse("Should return false if task already completed", future.cancel(true));
-		assertFalse(future.isCancelled());
-	}
-
-}