Subscribers to channel-wrapping Flux instances should broadcast

Fixes #640

spring-cloud-stream-reactive/src/main/java/org/springframework/cloud/stream/reactive/MessageChannelToInputFluxParameterAdapter.java

@@ -65,7 +65,7 @@ public class MessageChannelToInputFluxParameterAdapter
 				};
 				boundElement.subscribe(messageHandler);
 				emitter.setCancellation(() -> boundElement.unsubscribe(messageHandler));
-			});
+			}).publish().autoConnect();
 		}
 		else {
 			return Flux.create(emitter -> {
@@ -81,7 +81,7 @@ public class MessageChannelToInputFluxParameterAdapter
 				};
 				boundElement.subscribe(messageHandler);
 				emitter.setCancellation(() -> boundElement.unsubscribe(messageHandler));
-			});
+			}).publish().autoConnect();
 		}
 	}
 }

spring-cloud-stream-reactive/src/test/java/org/springframework/cloud/stream/reactive/MessageChannelToInputFluxParameterAdapterTests.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2016 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.cloud.stream.reactive;
+
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.Test;
+import reactor.core.publisher.Flux;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.integration.channel.DirectChannel;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.converter.CompositeMessageConverter;
+import org.springframework.messaging.converter.MappingJackson2MessageConverter;
+import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.util.ReflectionUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Marius Bogoevici
+ */
+public class MessageChannelToInputFluxParameterAdapterTests {
+
+	@Test
+	public void testWrapperFluxSupportsMultipleSubscriptions() throws Exception {
+		List<String> results = Collections.synchronizedList(new ArrayList<>());
+		CountDownLatch latch = new CountDownLatch(4);
+		final MessageChannelToInputFluxParameterAdapter messageChannelToInputFluxParameterAdapter
+				= new MessageChannelToInputFluxParameterAdapter(new CompositeMessageConverter(Collections.singleton(new MappingJackson2MessageConverter())));
+		final Method processMethod = ReflectionUtils.findMethod(MessageChannelToInputFluxParameterAdapterTests.class, "process", Flux.class);
+		final DirectChannel adaptedChannel = new DirectChannel();
+		final Flux<Message<?>> adapterFlux = (Flux<Message<?>>) messageChannelToInputFluxParameterAdapter.adapt(adaptedChannel, new MethodParameter(processMethod, 0));
+		String uuid1 = UUID.randomUUID().toString();
+		String uuid2 = UUID.randomUUID().toString();
+		adapterFlux.map(m -> m.getPayload() + uuid1).subscribe(s -> {
+			results.add(s);
+			latch.countDown();
+		});
+		adapterFlux.map(m -> m.getPayload() + uuid2).subscribe(s -> {
+			results.add(s);
+			latch.countDown();
+		});
+
+		adaptedChannel.send(MessageBuilder.withPayload("A").build());
+		adaptedChannel.send(MessageBuilder.withPayload("B").build());
+
+		assertThat(latch.await(5000, TimeUnit.MILLISECONDS)).isTrue();
+		assertThat(results).containsExactlyInAnyOrder("A" + uuid1, "B" + uuid1, "A" + uuid2, "B" + uuid2);
+
+	}
+
+	public void process(Flux<Message<?>> message) {
+		// do nothing
+	}
+}