GH-408 Enhance RoutingFunction with SpEL and application properties

- Added initial support for communicating routing instructions via SpEL thru both message headers and application properties
- Added support for communication function definition via application properties
- Added additional tests and updated documentation

Resolves #408

docs/src/main/asciidoc/spring-cloud-function.adoc

@@ -123,30 +123,49 @@ you to invoke a single function which acts as a router to an actual function you
 This feature is very useful in certain FAAS environments where maintaining configurations
 for several functions could be cumbersome or exposing more then one function is not possible.
 
-You enable this feature via `spring.cloud.function.routing.enabled` property setting it
+The `RoutingFunction` is registered in _FunctionCatalog_  under the name `functionRouter`. For simplicity
-to `true` (default is `false`).
+and consistency you can also refer to `RoutingFunction.FUNCTION_NAME` constant.
-This enables `RoutingFunction` under the name `router` which is loaded in FunctionCatalog.
 
 This function has the following signature:
 
 [source, java]
 ----
-public class RoutingFunction implements Function<Publisher<Message<?>>, Publisher<?>>, Consumer<Publisher<Message<?>>> {
+public class RoutingFunction implements Function<Object, Object> {
 . . .
 }
 ----
+The routing instructions could be communicated in several ways;
 
-This allows the above function to act as both `Function` and `Consumer`.
+*Message Headers*
-As you can see it takes `Message<?>` as an input argument. This allows you to communicate
-the name of the actual function you want to invoke by providing `function.name` Message header.
 
-In specific execution environments/models the adapters are responsible to translate and communicate `function.name`
+If the input argument is of type `Message<?>`, you can communicate routing instruction by setting one of
-via Message header. For example, when using _spring-cloud-function-web_ you can provide `function.name` as an HTTP
+`spring.cloud.function.definition` or `spring.cloud.function.routing-expression` Message headers.
+For more static cases you can use `spring.cloud.function.definition` header which allows you to provide
+the name of a single function (e.g., `...definition=foo`) or a composition instruction (e.g., `...definition=foo|bar|baz`).
+For more dynamic cases you can use `spring.cloud.function.routing-expression` header which allows
+you to use Spring Expression Language (SpEL) and provide SpEL expression that should resolve
+into definition of a function (as described above).
+
+NOTE: SpEL evaluation context's root object is the
+actual input argument, so in he case of `Message<?>` you can construct expression that has access
+to both `payload` and `headers` (e.g., `spring.cloud.function.routing-expression=headers.function_name`).
+
+In specific execution environments/models the adapters are responsible to translate and communicate
+`spring.cloud.function.definition` and/or `spring.cloud.function.routing-expression` via Message header.
+For example, when using _spring-cloud-function-web_ you can provide `spring.cloud.function.definition` as an HTTP
 header and the framework will propagate it as well as other HTTP headers as Message headers.
 
-Using Message also allows us to benefit from `MessageConverter`s to convert incoming request to the actual input type
+*Application Properties*
-of the target function
 
+Routing instruction can also be communicated via `spring.cloud.function.definition`
+or `spring.cloud.function.routing-expression` as application properties. The rules described in the
+previous section apply here as well. The only difference is you provide these instructions as
+application properties (e.g., `--spring.cloud.function.definition=foo`).
+
+IMPORTANT: When dealing with reactive inputs (e.g., Publisher), routing instructions must only be provided via Function properties. This is
+due to the nature of the reactive functions which are invoked only once to pass a Publisher and the rest
+is handled by the reactor, hence we can not access and/or rely on the routing instructions communicated via individual
+values (e.g., Message).
 
 === Kotlin Lambda support
 

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/FunctionProperties.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2019-2019 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
+ *
+ *      https://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.context;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+
+/**
+ *
+ * @author Oleg Zhurakousky
+ * @since 3.0
+ *
+ */
+@ConfigurationProperties(prefix = FunctionProperties.PREFIX)
+public class FunctionProperties {
+
+	/**
+	 * The name prefix for properties defined by this properties class.
+	 */
+	public final static String PREFIX = "spring.cloud.function";
+
+	/**
+	 * Definition of the function to be used. This could be function name (e.g., 'myFunction')
+	 * or function composition definition (e.g., 'myFunction|yourFunction')
+	 */
+	private String definition;
+
+	/**
+	 * SpEL expression which should result in function definition (e.g., function name or composition instruction).
+	 * NOTE: SpEL evaluation context's root object is the input argument (e.g., Message).
+	 */
+	private String routingExpression;
+
+	public String getDefinition() {
+		return definition;
+	}
+
+	public void setDefinition(String definition) {
+		this.definition = definition;
+	}
+
+	public String getRoutingExpression() {
+		return routingExpression;
+	}
+
+	public void setRoutingExpression(String routingExpression) {
+		this.routingExpression = routingExpression;
+	}
+}

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/BeanFactoryAwareFunctionRegistry.java

@@ -54,6 +54,7 @@ import org.springframework.cloud.function.context.FunctionRegistration;
 import org.springframework.cloud.function.context.FunctionRegistry;
 import org.springframework.cloud.function.context.FunctionType;
 import org.springframework.cloud.function.context.config.FunctionContextUtils;
+import org.springframework.cloud.function.context.config.RoutingFunction;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
 import org.springframework.context.ConfigurableApplicationContext;
@@ -213,9 +214,13 @@ public class BeanFactoryAwareFunctionRegistry
 
 	private String discoverDefaultDefinitionIfNecessary(String definition) {
 		if (StringUtils.isEmpty(definition)) {
-			String[] functionNames  = Stream.of(this.applicationContext.getBeanNamesForType(Function.class)).filter(n -> !n.startsWith("_")).toArray(String[]::new);
+			// the underscores are for Kotlin function registrations (see KotlinLambdaToFunctionAutoConfiguration)
-			String[] consumerNames  = Stream.of(this.applicationContext.getBeanNamesForType(Consumer.class)).filter(n -> !n.startsWith("_")).toArray(String[]::new);
+			String[] functionNames  = Stream.of(this.applicationContext.getBeanNamesForType(Function.class))
-			String[] supplierNames  = Stream.of(this.applicationContext.getBeanNamesForType(Supplier.class)).filter(n -> !n.startsWith("_")).toArray(String[]::new);
+					.filter(n -> !n.startsWith("_") && !n.equals(RoutingFunction.FUNCTION_NAME)).toArray(String[]::new);
+			String[] consumerNames  = Stream.of(this.applicationContext.getBeanNamesForType(Consumer.class))
+					.filter(n -> !n.startsWith("_") && !n.equals(RoutingFunction.FUNCTION_NAME)).toArray(String[]::new);
+			String[] supplierNames  = Stream.of(this.applicationContext.getBeanNamesForType(Supplier.class))
+					.filter(n -> !n.startsWith("_") && !n.equals(RoutingFunction.FUNCTION_NAME)).toArray(String[]::new);
 			/*
 			 * we may need to add BiFunction and BiConsumer at some point
 			 */
@@ -454,15 +459,11 @@ public class BeanFactoryAwareFunctionRegistry
 		}
 
 		public boolean isConsumer() {
-			return this.target instanceof Consumer;
+			return FunctionTypeUtils.isConsumer(this.functionType);
-		}
-
-		public boolean isFunction() {
-			return this.target instanceof Function;
 		}
 
 		public boolean isSupplier() {
-			return this.target instanceof Supplier;
+			return FunctionTypeUtils.isSupplier(this.functionType);
 		}
 
 		public Object getTarget() {
@@ -528,6 +529,11 @@ public class BeanFactoryAwareFunctionRegistry
 					Publisher<?> publisher = FunctionTypeUtils.isFlux(type)
 							? input == null ? Flux.empty() : Flux.just(input)
 									: input == null ? Mono.empty() : Mono.just(input);
+					if (logger.isDebugEnabled()) {
+						logger.debug("Invoking reactive function '" + this.functionType + "' with non-reactive input "
+								+ "should at least assume reactive output (e.g., Function<String, Flux<String>> f3 = catalog.lookup(\"echoFlux\");), "
+								+ "otherwise invocation will result in ClassCastException.");
+					}
 					result = this.invokeFunction(this.convertInputPublisherIfNecessary(publisher, FunctionTypeUtils.getInputType(this.functionType, 0)));
 				}
 				else {

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/catalog/FunctionInspector.java

@@ -20,10 +20,12 @@ import java.util.Collections;
 import java.util.Set;
 
 import org.springframework.cloud.function.context.FunctionRegistration;
+import org.springframework.cloud.function.context.catalog.BeanFactoryAwareFunctionRegistry.FunctionInvocationWrapper;
+import org.springframework.cloud.function.context.config.RoutingFunction;
 
 /**
  * @author Dave Syer
- *
+ * @author Oleg Zhurakousky
  */
 public interface FunctionInspector {
 
@@ -31,6 +33,11 @@ public interface FunctionInspector {
 
 	default boolean isMessage(Object function) {
 		FunctionRegistration<?> registration = getRegistration(function);
+		if (registration != null && registration.getTarget() instanceof FunctionInvocationWrapper
+				&& ((FunctionInvocationWrapper) registration.getTarget()).getTarget() instanceof RoutingFunction) {
+			// we always want to give routing function as much information as possible
+			return true;
+		}
 		return registration == null ? false : registration.getType().isMessage();
 	}
 

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/config/ContextFunctionCatalogAutoConfiguration.java

@@ -17,7 +17,6 @@
 package org.springframework.cloud.function.context.config;
 
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
@@ -32,7 +31,9 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.cloud.function.context.FunctionCatalog;
+import org.springframework.cloud.function.context.FunctionProperties;
 import org.springframework.cloud.function.context.FunctionRegistry;
 import org.springframework.cloud.function.context.catalog.BeanFactoryAwareFunctionRegistry;
 import org.springframework.cloud.function.context.catalog.FunctionInspector;
@@ -63,6 +64,7 @@ import org.springframework.util.CollectionUtils;
  */
 @Configuration(proxyBeanMethods = false)
 @ConditionalOnMissingBean(FunctionCatalog.class)
+@EnableConfigurationProperties(FunctionProperties.class)
 public class ContextFunctionCatalogAutoConfiguration {
 
 	static final String PREFERRED_MAPPER_PROPERTY = "spring.http.converters.preferred-json-mapper";
@@ -95,14 +97,8 @@ public class ContextFunctionCatalogAutoConfiguration {
 	}
 
 	@Bean(RoutingFunction.FUNCTION_NAME)
-	@ConditionalOnProperty(name = "spring.cloud.function.routing.enabled", havingValue = "true")
+	RoutingFunction functionRouter(FunctionCatalog functionCatalog, FunctionInspector functionInspector, FunctionProperties functionProperties) {
-	RoutingFunction gateway(FunctionCatalog functionCatalog, FunctionInspector functionInspector) {
+		return new RoutingFunction(functionCatalog, functionInspector, functionProperties);
-		Collection<MessageConverter> messageConverters = new ArrayList<MessageConverter>();
-		messageConverters.add(new MappingJackson2MessageConverter());
-		messageConverters.add(new StringMessageConverter());
-		messageConverters.add(new ByteArrayMessageConverter());
-		CompositeMessageConverter messageConverter = new CompositeMessageConverter(messageConverters);
-		return new RoutingFunction(functionCatalog, functionInspector, messageConverter);
 	}
 
 	@Configuration(proxyBeanMethods = false)

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/config/RoutingFunction.java

@@ -16,98 +16,168 @@
 
 package org.springframework.cloud.function.context.config;
 
+import java.lang.reflect.Type;
 import java.util.function.Function;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
-import reactor.core.publisher.SignalType;
+import reactor.core.publisher.Mono;
 
 import org.springframework.cloud.function.context.FunctionCatalog;
+import org.springframework.cloud.function.context.FunctionProperties;
 import org.springframework.cloud.function.context.catalog.FunctionInspector;
+import org.springframework.cloud.function.context.catalog.FunctionTypeUtils;
+import org.springframework.context.expression.MapAccessor;
+import org.springframework.expression.Expression;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.messaging.Message;
-import org.springframework.messaging.MessageHeaders;
-import org.springframework.messaging.converter.MessageConverter;
-import org.springframework.messaging.support.MessageBuilder;
 import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
 
 /**
  * An implementation of Function which acts as a gateway/router by actually
- * delegating incoming invocation to a function specified via `function.name`
+ * delegating incoming invocation to a function specified .. .
- * message header. <br>
- * {@link Message} is used as a canonical representation of a request which
- * contains some metadata and it is the responsibility of the higher level
- * framework to convert the incoming request into a Message. For example;
- * spring-cloud-function-web will create Message from HttpRequest copying all
- * HTTP headers as message headers.
  *
  * @author Oleg Zhurakousky
  * @since 2.1
  *
  */
-public class RoutingFunction implements Function<Publisher<Message<?>>, Publisher<?>> {
+public class RoutingFunction implements Function<Object, Object> {
 
 	/**
 	 * The name of this function use by BeanFactory.
 	 */
-	public static final String FUNCTION_NAME = "router";
+	public static final String FUNCTION_NAME = "functionRouter";
+
+	private static Log logger = LogFactory.getLog(RoutingFunction.class);
+
+	private final StandardEvaluationContext evalContext = new StandardEvaluationContext();
+
+	private final SpelExpressionParser spelParser = new SpelExpressionParser();
 
 	private final FunctionCatalog functionCatalog;
 
+	private final FunctionProperties functionProperties;
+
 	private final FunctionInspector functionInspector;
 
-	private final MessageConverter messageConverter;
+	public RoutingFunction(FunctionCatalog functionCatalog, FunctionInspector functionInspector, FunctionProperties functionProperties) {
-
-	RoutingFunction(FunctionCatalog functionCatalog, FunctionInspector functionInspector,
-			MessageConverter messageConverter) {
 		this.functionCatalog = functionCatalog;
+		this.functionProperties = functionProperties;
 		this.functionInspector = functionInspector;
-		this.messageConverter = messageConverter;
+		this.evalContext.addPropertyAccessor(new MapAccessor());
 	}
 
-	@SuppressWarnings("unchecked")
 	@Override
-	public Publisher<?> apply(Publisher<Message<?>> input) {
+	public Object apply(Object input) {
-		return Flux.from(input)
+		return this.route(input, input instanceof Publisher);
-				.switchOnFirst((signal, flux) -> {
+	}
-					Assert.isTrue(signal.hasValue()
+
-							&& signal.getType() == SignalType.ON_NEXT, "Signal has no value or wrong type " + signal);
+	/*
-					Function<Flux<Object>, Publisher<Object>> function = this.getRouteToFunction(signal.get());
+	 * - Check if function-name is set in header and if it is use it.
-					return flux.map(message -> {
+	 * If NOT
-						Object inputValue = this.convertInput(message, function);
+	 * - Check routing-expression and if it is set use it
-						return inputValue;
+	 * If NOT
-					})
+	 * - Check function-name is set in FunctionProperties and if it is use it
-					.log()
+	 * If NOT
-					.doOnError(error -> {
+	 * - Fail
-						throw new IllegalStateException("Failed to convert Message. Possible reason; "
+	 */
-								+ "No suitable converter was found for payload with 'contentType' "
+	@SuppressWarnings({ "rawtypes", "unchecked" })
-								+ signal.get().getHeaders().get(MessageHeaders.CONTENT_TYPE), error);
+	private Object route(Object input, boolean originalInputIsPublisher) {
-					})
+		Function function;
-					.transform(function);
+		if (input instanceof Message) {
-		});
+			Message<?> message = (Message<?>) input;
+			if (StringUtils.hasText((String) message.getHeaders().get("spring.cloud.function.definition"))) {
+				function = functionFromDefinition((String) message.getHeaders().get("spring.cloud.function.definition"));
+				Type functionType = functionInspector.getRegistration(function).getType().getType();
+				if (FunctionTypeUtils.isReactive(FunctionTypeUtils.getInputType(functionType, 0))) {
+					this.assertOriginalInputIsNotPublisher(originalInputIsPublisher);
+				}
+			}
+			else if (StringUtils.hasText((String) message.getHeaders().get("spring.cloud.function.routing-expression"))) {
+				function = this.functionFromExpression((String) message.getHeaders().get("spring.cloud.function.routing-expression"), message);
+				Type functionType = functionInspector.getRegistration(function).getType().getType();
+				if (FunctionTypeUtils.isReactive(FunctionTypeUtils.getInputType(functionType, 0))) {
+					this.assertOriginalInputIsNotPublisher(originalInputIsPublisher);
+				}
+			}
+			else if (StringUtils.hasText(functionProperties.getRoutingExpression())) {
+				function = this.functionFromExpression(functionProperties.getRoutingExpression(), message);
+			}
+			else if (StringUtils.hasText(functionProperties.getDefinition())) {
+				function = functionFromDefinition(functionProperties.getDefinition());
+			}
+			else {
+				throw new IllegalStateException("Failed to establish route, since neither were provided: "
+						+ "'spring.cloud.function.definition' as Message header or as application property or "
+						+ "'spring.cloud.function.routing-expression' as application property.");
+			}
+		}
+		else if (input instanceof Publisher) {
+			if (StringUtils.hasText(functionProperties.getRoutingExpression())) {
+				function = this.functionFromExpression(functionProperties.getRoutingExpression(), input);
+			}
+			else
+			if (StringUtils.hasText(functionProperties.getDefinition())) {
+				function = functionFromDefinition(functionProperties.getDefinition());
+			}
+			else {
+				return input instanceof Mono
+						? Mono.from((Publisher<?>) input).map(v -> route(v, originalInputIsPublisher))
+								: Flux.from((Publisher<?>) input).map(v -> route(v, originalInputIsPublisher));
+			}
+		}
+		else {
+			this.assertOriginalInputIsNotPublisher(originalInputIsPublisher);
+			if (StringUtils.hasText(functionProperties.getRoutingExpression())) {
+				function = this.functionFromExpression(functionProperties.getRoutingExpression(), input);
+			}
+			else
+			if (StringUtils.hasText(functionProperties.getDefinition())) {
+				function = functionFromDefinition(functionProperties.getDefinition());
+			}
+			else {
+				throw new IllegalStateException("Failed to establish route, since neither were provided: "
+						+ "'spring.cloud.function.definition' as Message header or as application property or "
+						+ "'spring.cloud.function.routing-expression' as application property.");
+			}
+		}
+
+		return function.apply(input);
+	}
+
+	private void assertOriginalInputIsNotPublisher(boolean originalInputIsPublisher) {
+		Assert.isTrue(!originalInputIsPublisher, "Routing input of type Publisher is not supported per individual "
+				+ "values (e.g., message header or POJO). Instead you should use 'spring.cloud.function.definition' or "
+				+ "spring.cloud.function.routing-expression' as application properties.");
 	}
 
 	@SuppressWarnings("rawtypes")
-	private Function getRouteToFunction(Message<?> message) {
+	private Function functionFromDefinition(String definition) {
-		String routeToFunctionName = (String) message.getHeaders().get("function.name");
+		Function function = functionCatalog.lookup(definition);
-		Assert.hasText(routeToFunctionName, "A 'function.name' was not provided as message header.");
+		Assert.notNull(function, "Failed to lookup function to route based on the value of 'spring.cloud.function.definition' property '"
-		Function function = functionCatalog.lookup(routeToFunctionName);
+				+ functionProperties.getDefinition() + "'");
-		Assert.notNull(function, "Failed to locate function specified with 'function.name':"
+		if (logger.isInfoEnabled()) {
-				+ message.getHeaders().get("function.name"));
+			logger.info("Resolved function from provided [definition] property " + functionProperties.getDefinition());
+		}
 		return function;
 	}
 
-	private Object convertInput(Message<?> message, Object function) {
+	@SuppressWarnings("rawtypes")
-		Class<?> inputType = functionInspector.getInputType(function);
+	private Function functionFromExpression(String routingExpression, Object input) {
-		Object inputValue = message.getPayload();
+		Expression expression = spelParser.parseExpression(routingExpression);
-		if (!inputValue.getClass().isAssignableFrom(inputType)) {
+		String functionName = expression.getValue(this.evalContext, input, String.class);
-			inputValue = this.messageConverter.fromMessage(message, functionInspector.getInputType(function));
+		Assert.hasText(functionName, "Failed to resolve function name based on routing expression '" + functionProperties.getRoutingExpression() + "'");
+		Function function = functionCatalog.lookup(functionName);
+		Assert.notNull(function, "Failed to lookup function to route to based on the expression '"
+				+ functionProperties.getRoutingExpression() + "' whcih resolved to '" + functionName + "' function name.");
+		if (logger.isInfoEnabled()) {
+			logger.info("Resolved function from provided [routing-expression]  " + routingExpression);
 		}
-		if (this.functionInspector.isMessage(function)) {
+		return function;
-			inputValue = MessageBuilder.createMessage(inputValue, message.getHeaders());
-		}
-		Assert.notNull(inputValue, "Failed to determine input value of type "
-				+ inputType + " from Message '"
-				+ message + "'. No suitable Message Converter found.");
-		return inputValue;
 	}
 }

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/config/RoutingFunctionTests.java

@@ -0,0 +1,187 @@
+/*
+ * Copyright 2019-2019 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
+ *
+ *      https://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.context.config;
+
+import java.util.function.Function;
+
+import org.junit.After;
+import org.junit.Test;
+import reactor.core.publisher.Flux;
+
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.cloud.function.context.FunctionCatalog;
+import org.springframework.cloud.function.context.FunctionProperties;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.support.MessageBuilder;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.fail;
+
+/**
+ *
+ * @author Oleg Zhurakousky
+ *
+ */
+public class RoutingFunctionTests {
+
+	private ConfigurableApplicationContext context;
+
+	@After
+	public void before() {
+		System.clearProperty("spring.cloud.function.definition");
+		System.clearProperty("spring.cloud.function.routing-expression");
+		context.close();
+	}
+
+	private FunctionCatalog configureCatalog() {
+		context = new SpringApplicationBuilder(RoutingFunctionConfiguration.class).run(
+				"--logging.level.org.springframework.cloud.function=DEBUG",
+				"--spring.cloud.function.routing.enabled=true");
+		FunctionCatalog catalog = context.getBean(FunctionCatalog.class);
+		return catalog;
+	}
+
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	@Test
+	public void testInvocationWithMessageAndHeader() {
+		FunctionCatalog functionCatalog = this.configureCatalog();
+		Function function = functionCatalog.lookup(RoutingFunction.FUNCTION_NAME);
+		assertThat(function).isNotNull();
+		Message<String> message = MessageBuilder.withPayload("hello")
+				.setHeader(FunctionProperties.PREFIX + ".definition", "reverse").build();
+		assertThat(function.apply(message)).isEqualTo("olleh");
+	}
+
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	@Test
+	public void testRoutingSimpleInputWithReactiveFunctionWithMessageHeader() {
+		FunctionCatalog functionCatalog = this.configureCatalog();
+		Function function = functionCatalog.lookup(RoutingFunction.FUNCTION_NAME);
+		assertThat(function).isNotNull();
+		Message<String> message = MessageBuilder.withPayload("hello")
+				.setHeader(FunctionProperties.PREFIX + ".definition", "echoFlux").build();
+		assertThat(((Flux) function.apply(message)).blockFirst()).isEqualTo("hello");
+	}
+
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	@Test(expected = Exception.class)
+	public void testRoutingReactiveInputWithReactiveFunctionAndDefinitionMessageHeader() {
+		FunctionCatalog functionCatalog = this.configureCatalog();
+		Function function = functionCatalog.lookup(RoutingFunction.FUNCTION_NAME);
+		assertThat(function).isNotNull();
+		Message<String> message = MessageBuilder.withPayload("hello")
+				.setHeader(FunctionProperties.PREFIX + ".definition", "echoFlux").build();
+		Flux resultFlux = (Flux) function.apply(Flux.just(message));
+		resultFlux.subscribe();
+	}
+
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	@Test(expected = Exception.class)
+	public void testRoutingReactiveInputWithReactiveFunctionAndExpressionMessageHeader() {
+		FunctionCatalog functionCatalog = this.configureCatalog();
+		Function function = functionCatalog.lookup(RoutingFunction.FUNCTION_NAME);
+		assertThat(function).isNotNull();
+		Message<String> message = MessageBuilder.withPayload("hello")
+				.setHeader(FunctionProperties.PREFIX + ".routing-expression", "'echoFlux'").build();
+		Flux resultFlux = (Flux) function.apply(Flux.just(message));
+		resultFlux.subscribe();
+	}
+
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	@Test
+	public void testInvocationWithMessageAndDefinitionProperty() {
+		System.setProperty(FunctionProperties.PREFIX + ".definition", "reverse");
+		FunctionCatalog functionCatalog = this.configureCatalog();
+		Function function = functionCatalog.lookup(RoutingFunction.FUNCTION_NAME);
+		assertThat(function).isNotNull();
+		Message<String> message = MessageBuilder.withPayload("hello").build();
+		assertThat(function.apply(message)).isEqualTo("olleh");
+	}
+
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	@Test
+	public void testInvocationWithMessageAndRoutingExpression() {
+		System.setProperty(FunctionProperties.PREFIX + ".routing-expression", "headers.function_name");
+		FunctionCatalog functionCatalog = this.configureCatalog();
+		Function function = functionCatalog.lookup(RoutingFunction.FUNCTION_NAME);
+		assertThat(function).isNotNull();
+		Message<String> message = MessageBuilder.withPayload("hello").setHeader("function_name", "reverse").build();
+		assertThat(function.apply(message)).isEqualTo("olleh");
+	}
+
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	@Test
+	public void testOtherExpectedFailures() {
+		FunctionCatalog functionCatalog = this.configureCatalog();
+		Function function = functionCatalog.lookup(RoutingFunction.FUNCTION_NAME);
+		// no function.definition header or function property
+		try {
+			function.apply(MessageBuilder.withPayload("hello").build());
+			fail();
+		}
+		catch (Exception e) {
+			//ignore
+		}
+
+		// non existing function
+		try {
+			function.apply(MessageBuilder.withPayload("hello").setHeader(FunctionProperties.PREFIX + ".definition", "blah").build());
+			fail();
+		}
+		catch (Exception e) {
+			//ignore
+		}
+	}
+
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	@Test
+	public void testInvocationWithMessageComposed() {
+		FunctionCatalog functionCatalog = this.configureCatalog();
+
+		Function function = functionCatalog.lookup(RoutingFunction.FUNCTION_NAME + "|uppercase");
+		assertThat(function).isNotNull();
+
+		Message<String> message = MessageBuilder.withPayload("hello")
+				.setHeader(FunctionProperties.PREFIX + ".definition", "uppercase").build();
+
+		assertThat(function.apply(message)).isEqualTo("HELLO");
+	}
+
+	@EnableAutoConfiguration
+	@Configuration
+	protected static class RoutingFunctionConfiguration {
+
+		@Bean
+		public Function<String, String> reverse() {
+			return v -> new StringBuilder(v).reverse().toString();
+		}
+
+		@Bean
+		public Function<String, String> uppercase() {
+			return v -> v.toUpperCase();
+		}
+
+		@Bean
+		public Function<Flux<String>, Flux<String>> echoFlux() {
+			return f -> f;
+		}
+	}
+}

spring-cloud-function-deployer/src/main/java/org/springframework/cloud/function/deployer/FunctionArchiveDeployer.java

@@ -67,7 +67,7 @@ class FunctionArchiveDeployer extends JarLauncher {
 	}
 
 	@SuppressWarnings({ "unchecked", "rawtypes" })
-	void deploy(FunctionRegistry functionRegistry, FunctionProperties functionProperties, String[] args) {
+	void deploy(FunctionRegistry functionRegistry, FunctionDeployerProperties functionProperties, String[] args) {
 		ClassLoader currentLoader = Thread.currentThread().getContextClassLoader();
 
 		try {
@@ -165,7 +165,7 @@ class FunctionArchiveDeployer extends JarLauncher {
 				|| name.startsWith("reactor.");
 	}
 
-	private String discoverFunctionClassName(FunctionProperties functionProperties) {
+	private String discoverFunctionClassName(FunctionDeployerProperties functionProperties) {
 		try {
 			return StringUtils.hasText(functionProperties.getFunctionClass())
 					? functionProperties.getFunctionClass()

spring-cloud-function-deployer/src/main/java/org/springframework/cloud/function/deployer/FunctionDeployerConfiguration.java

@@ -33,11 +33,16 @@ import org.springframework.boot.env.EnvironmentPostProcessor;
 import org.springframework.boot.loader.archive.Archive;
 import org.springframework.boot.loader.archive.ExplodedArchive;
 import org.springframework.boot.loader.archive.JarFileArchive;
+import org.springframework.cloud.function.context.FunctionProperties;
 import org.springframework.cloud.function.context.FunctionRegistry;
 import org.springframework.context.SmartLifecycle;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.MapPropertySource;
+import org.springframework.core.env.MutablePropertySources;
+import org.springframework.core.env.PropertiesPropertySource;
+import org.springframework.util.StringUtils;
 
 /**
  *
@@ -52,13 +57,13 @@ import org.springframework.core.env.ConfigurableEnvironment;
  *
  */
 @Configuration(proxyBeanMethods = false)
-@EnableConfigurationProperties(FunctionProperties.class)
+@EnableConfigurationProperties(FunctionDeployerProperties.class)
 public class FunctionDeployerConfiguration {
 
 	private static Log logger = LogFactory.getLog(FunctionDeployerConfiguration.class);
 
 	@Bean
-	SmartLifecycle functionArchiveDeployer(FunctionProperties functionProperties,
+	SmartLifecycle functionArchiveDeployer(FunctionDeployerProperties functionProperties,
 			FunctionRegistry functionRegistry, ApplicationArguments arguments) {
 
 		ApplicationArguments updatedArguments = this.updateArguments(arguments);
@@ -123,14 +128,14 @@ public class FunctionDeployerConfiguration {
 	}
 
 	/*
-	 * We need to update actual arguments to ensure that when we may be passing to the deployed archive has the right properties.
+	 * We need to update the actual arguments with non-legacy properties before passing these arguments to the deployable archive.
-	 * For the current application FunctionProperties already set as a result of EnvironmentPostProcessor
+	 * For the current application FunctionProperties already updated and set as a result of EnvironmentPostProcessor
 	 */
 	private ApplicationArguments updateArguments(ApplicationArguments arguments) {
 		List<String> originalArguments =  new ArrayList<String>(Arrays.asList(arguments.getSourceArgs()));
 
 		if (arguments.containsOption("function.name")) {
-			originalArguments.add(FunctionProperties.PREFIX + ".function-name=" + arguments.getOptionValues("function.name").get(0));
+			originalArguments.add(FunctionProperties.PREFIX + ".definition=" + arguments.getOptionValues("function.name").get(0));
 		}
 		if (arguments.containsOption("function.location")) {
 			originalArguments.add(FunctionProperties.PREFIX + ".location=" + arguments.getOptionValues("function.location").get(0));
@@ -147,11 +152,16 @@ public class FunctionDeployerConfiguration {
 	static class LegacyPropertyEnvironmentPostProcessor implements EnvironmentPostProcessor {
 		@Override
 		public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
-			if (environment.containsProperty("function.name")) {
+		String functionName = environment.containsProperty("function.name") ? environment.getProperty("function.name") : null;
-				System.setProperty(FunctionProperties.PREFIX + ".function-name", environment.getProperty("function.name"));
+			String functionLocation = environment.containsProperty("function.location") ? environment.getProperty("function.location") : null;
-			}
+			if (StringUtils.hasText(functionName) || StringUtils.hasText(functionLocation)) {
-			if (environment.containsProperty("function.location")) {
+				MutablePropertySources propertySources = environment.getPropertySources();
-				System.setProperty(FunctionProperties.PREFIX + ".location", environment.getProperty("function.location"));
+				propertySources.forEach(ps -> {
+					if (ps instanceof PropertiesPropertySource) {
+						((MapPropertySource) ps).getSource().put(FunctionProperties.PREFIX + ".definition", functionName);
+						((MapPropertySource) ps).getSource().put(FunctionProperties.PREFIX + ".location", functionLocation);
+					}
+				});
 			}
 		}
 	}

spring-cloud-function-deployer/src/main/java/org/springframework/cloud/function/deployer/FunctionDeployerProperties.java

@@ -19,22 +19,19 @@ package org.springframework.cloud.function.deployer;
 import javax.annotation.PostConstruct;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.cloud.function.context.FunctionProperties;
 import org.springframework.util.Assert;
-import org.springframework.util.StringUtils;
 
 /**
  * Configuration properties for deciding how to locate the functional class to execute.
  *
  * @author Eric Bottard
  * @author Oleg Zhurakousky
+ *
+ * @see FunctionProperties
  */
-@ConfigurationProperties("spring.cloud.function")
+@ConfigurationProperties(prefix = FunctionProperties.PREFIX)
-public class FunctionProperties {
+public class FunctionDeployerProperties {
-
-	/**
-	 * The name prefix for properties defined by this properties class.
-	 */
-	public final static String PREFIX = "spring.cloud.function";
 
 	/**
 	 * Location of jar archive containing the supplier/function/consumer class or bean to run.
@@ -42,12 +39,7 @@ public class FunctionProperties {
 	private String location;
 
 	/**
-	 * The name of the function to be looked up from the FunctionCatalog (e.g., bean name).
+	 * The name of the function class to be instantiated and loaded into FunctionCatalog. The name of the
-	 */
-	private String functionName;
-
-	/**
-	 * The name of the function class tyo be instantiated and loaded into FunctionCatalog. The name of the
 	 * function will be decapitalized simple name of this class.
 	 */
 	private String functionClass;
@@ -60,14 +52,6 @@ public class FunctionProperties {
 		return this.functionClass;
 	}
 
-	public void setFunctionName(String functionName) {
-		this.functionName = StringUtils.hasText(functionName) ? functionName : "";
-	}
-
-	public String getFunctionName() {
-		return this.functionName;
-	}
-
 	public String getLocation() {
 		return this.location;
 	}

spring-cloud-function-web/src/test/java/org/springframework/cloud/function/web/mvc/RoutingFunctionTests.java

@@ -31,6 +31,7 @@ import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
 import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.cloud.function.context.FunctionProperties;
 import org.springframework.cloud.function.context.config.RoutingFunction;
 import org.springframework.cloud.function.web.RestApplication;
 import org.springframework.cloud.function.web.mvc.RoutingFunctionTests.TestConfiguration;
@@ -42,6 +43,7 @@ import org.springframework.http.RequestEntity;
 import org.springframework.http.ResponseEntity;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit4.SpringRunner;
 
@@ -57,18 +59,23 @@ import static org.assertj.core.api.Assertions.assertThat;
 		"spring.cloud.function.web.path=/functions",
 		"spring.cloud.function.routing.enabled=true"})
 @ContextConfiguration(classes = { RestApplication.class, TestConfiguration.class })
-@Ignore
 public class RoutingFunctionTests {
 
 	@Autowired
 	private TestRestTemplate rest;
 
+	@Autowired
+	private FunctionProperties functionProperties;
+
+
 	@Test
+	@DirtiesContext
 	public void testFunctionMessage() throws Exception {
+
 		HttpEntity<String> postForEntity = this.rest
 				.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
 						.contentType(MediaType.APPLICATION_JSON)
-						.header("function.name", "employee")
+						.header("spring.cloud.function.definition", "employee")
 						.body("{\"name\":\"Bob\",\"age\":25}"), String.class);
 		assertThat(postForEntity.getBody()).isEqualTo("{\"name\":\"Bob\",\"age\":25}");
 		assertThat(postForEntity.getHeaders().containsKey("x-content-type")).isTrue();
@@ -78,55 +85,58 @@ public class RoutingFunctionTests {
 	}
 
 	@Test
+	@DirtiesContext
 	public void testFunctionPrimitive() throws Exception {
 		ResponseEntity<String> postForEntity = this.rest
 				.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
 						.contentType(MediaType.TEXT_PLAIN)
-						.header("function.name", "echo")
+						.header("spring.cloud.function.definition", "echo")
 						.body("{\"name\":\"Bob\",\"age\":25}"), String.class);
 		assertThat(postForEntity.getBody()).isEqualTo("{\"name\":\"Bob\",\"age\":25}");
 		assertThat(postForEntity.getStatusCode()).isEqualTo(HttpStatus.OK);
 	}
 
 	@Test
+	@DirtiesContext
 	public void testFluxFunctionPrimitive() throws Exception {
+		this.functionProperties.setDefinition("fluxuppercase");
 		ResponseEntity<String> postForEntity = this.rest
 				.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
 						.contentType(MediaType.TEXT_PLAIN)
-						.header("function.name", "fluxuppercase")
+						.body("[\"hello\", \"bye\"]"), String.class);
-						.body("hello"), String.class);
+		assertThat(postForEntity.getBody()).isEqualTo("[\"HELLO\", \"BYE\"]");
-		assertThat(postForEntity.getBody()).isEqualTo("[\"HELLO\"]");
 		assertThat(postForEntity.getStatusCode()).isEqualTo(HttpStatus.OK);
 
 		postForEntity = this.rest
 		.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
 				.contentType(MediaType.TEXT_PLAIN)
-				.header("function.name", "fluxuppercase")
 				.body("hello1"), String.class);
-		assertThat(postForEntity.getBody()).isEqualTo("[\"HELLO1\"]");
+		assertThat(postForEntity.getBody()).isEqualTo("HELLO1");
 		assertThat(postForEntity.getStatusCode()).isEqualTo(HttpStatus.OK);
 
 		postForEntity = this.rest
 		.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
 				.contentType(MediaType.TEXT_PLAIN)
-				.header("function.name", "fluxuppercase")
 				.body("hello2"), String.class);
-		assertThat(postForEntity.getBody()).isEqualTo("[\"HELLO2\"]");
+		assertThat(postForEntity.getBody()).isEqualTo("HELLO2");
 		assertThat(postForEntity.getStatusCode()).isEqualTo(HttpStatus.OK);
 	}
 
 	@Test
+	@DirtiesContext
 	public void testFluxFunctionPrimitiveArray() throws Exception {
+		this.functionProperties.setDefinition("fluxuppercase");
 		ResponseEntity<String> postForEntity = this.rest
 				.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
 						.contentType(MediaType.APPLICATION_JSON)
-						.header("function.name", "fluxuppercase")
 						.body(new String[] {"a", "b", "c"}), String.class);
 		assertThat(postForEntity.getBody()).isEqualTo("[\"A\",\"B\",\"C\"]");
 		assertThat(postForEntity.getStatusCode()).isEqualTo(HttpStatus.OK);
 	}
 
 	@Test
+	@DirtiesContext
+	@Ignore
 	public void testFluxConsumer() throws Exception {
 		ResponseEntity<String> postForEntity = this.rest
 				.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
@@ -134,10 +144,13 @@ public class RoutingFunctionTests {
 						.header("function.name", "fluxconsumer")
 						.body(new String[] {"a", "b", "c"}), String.class);
 		assertThat(postForEntity.getStatusCode()).isEqualTo(HttpStatus.OK);
+
 	}
 
 
 	@Test
+	@DirtiesContext
+	@Ignore
 	public void testFunctionPojo() throws Exception {
 		ResponseEntity<String> postForEntity = this.rest
 				.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
@@ -149,11 +162,13 @@ public class RoutingFunctionTests {
 	}
 
 	@Test
+	@DirtiesContext
+	@Ignore
 	public void testConsumerMessage() throws Exception {
 		ResponseEntity<String> postForEntity = this.rest
 				.exchange(RequestEntity.post(new URI("/functions/" + RoutingFunction.FUNCTION_NAME))
 						.contentType(MediaType.TEXT_PLAIN)
-						.header("function.name", "messageConsumer")
+						.header("spring.cloud.function.definition", "messageConsumer")
 						.body("{\"name\":\"Bob\",\"age\":25}"), String.class);
 		assertThat(postForEntity.getStatusCode()).isEqualTo(HttpStatus.OK);
 	}
@@ -237,8 +252,6 @@ public class RoutingFunctionTests {
 		public void setValue(String value) {
 			this.value = value;
 		}
-
-
 	}
 
 }