Tentatively fix streaming issues

* Assume that the Function returned by FunctionCatalog
  is already wrapped as Function<Flux<?>,Flux<?>>

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

@@ -89,7 +89,7 @@ public class StreamConfiguration {
 		public AbstractFunctionInvoker<?, ?> invoker(FunctionCatalog registry, FunctionInspector functionInspector,
 				@Lazy CompositeMessageConverterFactory compositeMessageConverterFactory) {
 			String name = properties.getEndpoint();
-			Function<Object, Object> function = registry.lookupFunction(name);
+			Function<Flux<?>, Flux<?>> function = registry.lookupFunction(name);
 			Assert.notNull(function, "no such function: " + name);
 			return new StreamListeningFunctionInvoker(name, function, functionInspector,
 					compositeMessageConverterFactory);

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

@@ -23,8 +23,6 @@ import reactor.core.publisher.Flux;
 import org.springframework.beans.factory.SmartInitializingSingleton;
 import org.springframework.cloud.function.context.FunctionInspector;
 import org.springframework.cloud.function.invoker.AbstractFunctionInvoker;
-import org.springframework.cloud.function.support.FluxFunction;
-import org.springframework.cloud.function.support.FunctionUtils;
 import org.springframework.cloud.stream.annotation.Input;
 import org.springframework.cloud.stream.annotation.Output;
 import org.springframework.cloud.stream.annotation.StreamListener;
@@ -32,7 +30,6 @@ 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;
 
 /**
  * @author Mark Fisher
@@ -51,9 +48,9 @@ public class StreamListeningFunctionInvoker extends AbstractFunctionInvoker<Flux
 
 	private Class<?> inputType;
 
-	public StreamListeningFunctionInvoker(String name, Function<?, ?> function, FunctionInspector functionInspector,
+	public StreamListeningFunctionInvoker(String name, Function<Flux<?>, Flux<?>> function, FunctionInspector functionInspector,
 			CompositeMessageConverterFactory converterFactory) {
-		super(wrapIfNecessary(function));
+		super(function);
 		this.name = name;
 		this.functionInspector = functionInspector;
 		this.converterFactory = converterFactory;
@@ -71,15 +68,6 @@ public class StreamListeningFunctionInvoker extends AbstractFunctionInvoker<Flux
 		return this.doInvoke(input.map(convertInput()));
 	}
 
-	@SuppressWarnings({ "rawtypes", "unchecked" })
-	private static Function<Flux<?>, Flux<?>> wrapIfNecessary(Function function) {
-		Assert.notNull(function, "Function must not be null");
-		if (!FunctionUtils.isFluxFunction(function)) {
-			function = new FluxFunction(function);
-		}
-		return function;
-	}
-
 	private Function<Message<?>, Object> convertInput() {
 		return m -> {
 			if (this.inputType.isAssignableFrom(m.getPayload().getClass())) {

spring-cloud-function-stream/src/test/java/org/springframework/cloud/function/stream/function/FluxPojoStreamingFunctionTests.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 reactor.core.publisher.Flux;
+
+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 = FluxPojoStreamingFunctionTests.StreamingFunctionApplication.class, properties = {
+		"spring.cloud.stream.bindings.input.destination=data-in",
+		"spring.cloud.stream.bindings.output.destination=data-out", "spring.cloud.function.stream.endpoint=uppercase" })
+public class FluxPojoStreamingFunctionTests {
+
+	@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<Foo>, Flux<Foo>> uppercase() {
+			return foos -> foos.map(f -> new Foo(f.getName().toUpperCase()));
+		}
+	}
+
+	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/FluxStreamingFunctionTests.java

@@ -0,0 +1,69 @@
+/*
+ * 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 reactor.core.publisher.Flux;
+
+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 = FluxStreamingFunctionTests.StreamingFunctionApplication.class, properties = {
+		"spring.cloud.stream.bindings.input.destination=data-in",
+		"spring.cloud.stream.bindings.output.destination=data-out",
+		"spring.cloud.function.stream.endpoint=uppercase" })
+public class FluxStreamingFunctionTests {
+
+	@Autowired
+	Processor processor;
+
+	@Autowired
+	MessageCollector messageCollector;
+
+	@Test
+	public void test() throws Exception {
+		processor.input().send(MessageBuilder.withPayload("foo").build());
+		Message<?> result = messageCollector.forChannel(processor.output()).poll(1000, TimeUnit.MILLISECONDS);
+		assertThat(result.getPayload()).isEqualTo("FOO");
+	}
+
+	@SpringBootApplication
+	public static class StreamingFunctionApplication {
+
+		@Bean
+		public Function<Flux<String>, Flux<String>> uppercase() {
+			return f-> f.map(s -> s.toUpperCase());
+		}
+	}
+}