Add support for Message<Foo> in stream apps

The FunctionInspector needs to be able to distinguish between a
function of Flux<Foo> and a function of Flux<Message<Foo>>. Then
it can do the conversion a level below.

Only supports Message->Message or POJO->POJO (no mixtures), so there
is only one new method in FunctionInspector.

No support in the web endpoints yet. But it's probably not so hard
to add.

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

@@ -93,7 +93,10 @@ public class StreamListeningConsumerInvoker implements SmartInitializingSingleto
 	private Function<Message<?>, Object> convertInput(String name) {
 		Class<?> inputType = functionInspector.getInputType(name);
 		return m -> {
-			if (inputType.isAssignableFrom(m.getPayload().getClass())) {
+			if (Message.class.isAssignableFrom(inputType)) {
+				return m;
+			}
+			else if (inputType.isAssignableFrom(m.getPayload().getClass())) {
 				return m.getPayload();
 			}
 			else {

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

@@ -28,7 +28,7 @@ import org.springframework.cloud.stream.converter.CompositeMessageConverterFacto
 import org.springframework.cloud.stream.messaging.Processor;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.converter.MessageConverter;
-import org.springframework.util.Assert;
+import org.springframework.messaging.support.MessageBuilder;
 
 import reactor.core.publisher.Flux;
 
@@ -96,12 +96,22 @@ public class StreamListeningFunctionInvoker implements SmartInitializingSingleto
 	private Function<Message<?>, Object> convertInput(String name) {
 		Class<?> inputType = functionInspector.getInputType(name);
 		return m -> {
-			if (inputType.isAssignableFrom(m.getPayload().getClass())) {
-				return m.getPayload();
+			if (functionInspector.isMessage(name)) {
+				return MessageBuilder.withPayload(convertPayload(name, inputType, m))
+						.copyHeaders(m.getHeaders()).build();
 			}
 			else {
-				return this.converter.fromMessage(m, inputType);
+				return convertPayload(name, inputType, m);
 			}
 		};
 	}
+
+	private Object convertPayload(String name, Class<?> inputType, Message<?> m) {
+		if (inputType.isAssignableFrom(m.getPayload().getClass())) {
+			return m.getPayload();
+		}
+		else {
+			return this.converter.fromMessage(m, inputType);
+		}
+	}
 }

spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/FluxMessagePojoStreamingFunctionTests.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2017 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.function.stream.function;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.stream.messaging.Processor;
+import org.springframework.cloud.stream.test.binder.MessageCollector;
+import org.springframework.context.annotation.Bean;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import reactor.core.publisher.Flux;
+
+/**
+ * @author Marius Bogoevici
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = FluxMessagePojoStreamingFunctionTests.StreamingFunctionApplication.class)
+public class FluxMessagePojoStreamingFunctionTests {
+
+	@Autowired
+	Processor processor;
+
+	@Autowired
+	MessageCollector messageCollector;
+
+	@Test
+	public void test() throws Exception {
+		processor.input().send(
+				MessageBuilder.withPayload(new String("{\"name\":\"foo\"}")).build());
+		Message<?> result = messageCollector.forChannel(processor.output()).poll(1000,
+				TimeUnit.MILLISECONDS);
+		assertThat(result.getPayload()).isInstanceOf(Foo.class);
+	}
+
+	@SpringBootApplication
+	public static class StreamingFunctionApplication {
+
+		@Bean
+		public Function<Flux<Message<Foo>>, Flux<Message<Foo>>> uppercase() {
+			return flux -> flux.map(f -> MessageBuilder
+					.withPayload(new Foo(f.getPayload().getName().toUpperCase()))
+					.build());
+		}
+	}
+
+	protected static class Foo {
+		private String name;
+
+		Foo() {
+		}
+
+		public Foo(String name) {
+			this.name = name;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+	}
+}

spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/MessagePojoStreamingFunctionTests.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2017 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.function.stream.function;
+
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.stream.messaging.Processor;
+import org.springframework.cloud.stream.test.binder.MessageCollector;
+import org.springframework.context.annotation.Bean;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Marius Bogoevici
+ */
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = MessagePojoStreamingFunctionTests.StreamingFunctionApplication.class)
+public class MessagePojoStreamingFunctionTests {
+
+	@Autowired
+	Processor processor;
+
+	@Autowired
+	MessageCollector messageCollector;
+
+	@Test
+	public void test() throws Exception {
+		processor.input().send(
+				MessageBuilder.withPayload(new String("{\"name\":\"foo\"}")).build());
+		Message<?> result = messageCollector.forChannel(processor.output()).poll(1000,
+				TimeUnit.MILLISECONDS);
+		assertThat(result.getPayload()).isInstanceOf(Foo.class);
+	}
+
+	@SpringBootApplication
+	public static class StreamingFunctionApplication {
+
+		@Bean
+		public Function<Message<Foo>, Message<Foo>> uppercase() {
+			return f -> MessageBuilder
+					.withPayload(new Foo(f.getPayload().getName().toUpperCase())).build();
+		}
+	}
+
+	protected static class Foo {
+		private String name;
+
+		Foo() {
+		}
+
+		public Foo(String name) {
+			this.name = name;
+		}
+
+		public String getName() {
+			return name;
+		}
+
+		public void setName(String name) {
+			this.name = name;
+		}
+	}
+}