StreamBridge's dynamic destinations should be closed on shutdown.

- if not, we might lose some messages on shutdown especially in case of kafka async mode producing.

Resolves #2835

core/spring-cloud-stream-integration-tests/src/test/java/org/springframework/cloud/stream/function/StreamBridgeTests.java

@@ -639,6 +639,25 @@ public class StreamBridgeTests {
 		}
 	}
 
+	@Test
+	void testDynamicDestinationDestroy() {
+		BindingService bindingService;
+		try (ConfigurableApplicationContext context = new SpringApplicationBuilder(TestChannelBinderConfiguration
+			.getCompleteConfiguration(InterceptorConfiguration.class))
+			.web(WebApplicationType.NONE).run(
+				"--spring.jmx.enabled=false",
+				"--spring.cloud.stream.dynamic-destination-cache-size=1"
+			)) {
+			StreamBridge bridge = context.getBean(StreamBridge.class);
+			bridge.send("a", "hello foo");
+
+			bindingService = context.getBean(BindingService.class);
+			assertThat(bindingService.getProducerBindingNames().length).isEqualTo(1);
+			assertThat(bindingService.getProducerBindingNames()[0]).isEqualTo("a");
+		}
+		assertThat(bindingService.getProducerBindingNames().length).isEqualTo(0);
+	}
+
 	@Test
 	void testWithIntegrationFlowBecauseMarcinSaidSo() {
 		try (ConfigurableApplicationContext context = new SpringApplicationBuilder(TestChannelBinderConfiguration

core/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/function/StreamBridge.java

@@ -26,6 +26,7 @@ import java.util.function.Function;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.SmartInitializingSingleton;
 import org.springframework.cloud.function.context.FunctionCatalog;
 import org.springframework.cloud.function.context.FunctionRegistration;
@@ -77,7 +78,7 @@ import org.springframework.util.StringUtils;
  *
  */
 @SuppressWarnings("rawtypes")
-public final class StreamBridge implements StreamOperations, SmartInitializingSingleton {
+public final class StreamBridge implements StreamOperations, SmartInitializingSingleton, DisposableBean {
 
 	private static final String STREAM_BRIDGE_FUNC_NAME = "streamBridge";
 
@@ -297,4 +298,11 @@ public final class StreamBridge implements StreamOperations, SmartInitializingSi
 			this.applicationContext.getBean(GlobalChannelInterceptorProcessor.class);
 		globalChannelInterceptorProcessor.postProcessAfterInitialization(messageChannel, destinationName);
 	}
+
+	@Override
+	public void destroy() throws Exception {
+		channelCache.keySet().forEach(bindingService::unbindProducers);
+		channelCache.clear();
+	}
+
 }