GH-786 Fix regression with RoutingFunction over AWS APIGateway

Resolves #786

spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/main/java/org/springframework/cloud/function/adapter/aws/FunctionInvoker.java

@@ -82,7 +82,7 @@ public class FunctionInvoker implements RequestStreamHandler {
 		this.start();
 	}
 
-	@SuppressWarnings("rawtypes")
+	@SuppressWarnings({ "rawtypes", "unchecked" })
 	@Override
 	public void handleRequest(InputStream input, OutputStream output, Context context) throws IOException {
 		final byte[] payload = StreamUtils.copyToByteArray(input);
@@ -99,10 +99,18 @@ public class FunctionInvoker implements RequestStreamHandler {
 
 
 		// TODO we should eventually completely delegate to message converter
-		//Message requestMessage = MessageBuilder.withPayload(payload).setHeader(AWSLambdaUtils.AWS_API_GATEWAY, true).build();
-		Message requestMessage = isApiGateway
-				? MessageBuilder.withPayload(payload).setHeader(AWSLambdaUtils.AWS_API_GATEWAY, true).build()
-				: AWSLambdaUtils.generateMessage(payload, new MessageHeaders(Collections.emptyMap()), function.getInputType(), this.jsonMapper, context);
+		Message requestMessage;
+		if (isApiGateway) {
+			MessageBuilder builder = MessageBuilder.withPayload(payload).setHeader(AWSLambdaUtils.AWS_API_GATEWAY, true);
+			if (structMessage instanceof Map && ((Map) structMessage).containsKey("headers")) {
+				builder.copyHeaders((Map) ((Map) structMessage).get("headers"));
+			}
+			requestMessage = builder.build();
+		}
+		else {
+			requestMessage = AWSLambdaUtils
+					.generateMessage(payload, new MessageHeaders(Collections.emptyMap()), function.getInputType(), this.jsonMapper, context);
+		}
 
 		try {
 			Object response = this.function.apply(requestMessage);
@@ -111,15 +119,20 @@ public class FunctionInvoker implements RequestStreamHandler {
 		}
 		catch (Exception e) {
 			logger.error(e);
-			StreamUtils.copy(this.buildExceptionResult(requestMessage, e), output);
+			StreamUtils.copy(this.buildExceptionResult(requestMessage, e, isApiGateway), output);
 		}
 	}
 
-	private byte[] buildExceptionResult(Message<?> requestMessage, Exception exception) throws IOException {
-		APIGatewayProxyResponseEvent event = new APIGatewayProxyResponseEvent();
-		event.setStatusCode(HttpStatus.EXPECTATION_FAILED.value());
-		event.setBody(exception.getMessage());
-		return this.jsonMapper.toJson(event);
+	private byte[] buildExceptionResult(Message<?> requestMessage, Exception exception, boolean isApiGateway) throws IOException {
+		if (isApiGateway) {
+			APIGatewayProxyResponseEvent event = new APIGatewayProxyResponseEvent();
+			event.setStatusCode(HttpStatus.EXPECTATION_FAILED.value());
+			event.setBody(exception.getMessage());
+			return this.jsonMapper.toJson(event);
+		}
+		else {
+			throw new IllegalStateException(exception);
+		}
 	}
 
 	@SuppressWarnings("unchecked")

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

@@ -137,7 +137,7 @@ public class RoutingFunction implements Function<Object, Object> {
 				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.");
+							+ "'spring.cloud.function.routing-expression' as application property. Incoming message: " + input);
 				}
 			}
 		}

spring-cloud-function-samples/function-sample-aws-routing/README.adoc

@@ -10,18 +10,17 @@ You can do so in two different ways.
 1. You can provide `spring_cloud_function_definition` environment variable setting its value to the desired function definition, which could also be composition
 (e.g., `spring_cloud_function_definition=foo|bar`).
 
-2. A more dynamic and recommended approach would be to fallback on auto routing capabilities of spring-cloud function's in AWS environment. 
-Basically every time you have more then one function in your configuration, the framework will bind 
-[Routing Function](https://docs.spring.io/spring-cloud-function/docs/3.1.3/reference/html/spring-cloud-function.html#_function_routing_and_filtering) 
-as AWS Lambda, and all you need to to is provide a routing instruction via Message headers or environment variables. The instructions could themselves be very dynamic, 
-since we support both SpEL and registering a callback interface. For more details on routing mechanisms please refer to 
-[Function Routing and Filtering](https://docs.spring.io/spring-cloud-function/docs/3.1.3/reference/html/spring-cloud-function.html#_function_routing_and_filtering) section.
-
-
 NOTE: Keep in mind though that since AWS does not allow dots `.` and/or hyphens`-` in the name of the environment variable, you can benefit from boot support and simply substitute
 dots with underscores and hyphens with camel case.  So for example `spring.cloud.function.definition` becomes `spring_cloud_function_definition`
 and `spring.cloud.function.routing-expression` becomes `spring_cloud_function_routingExpression`.
 
+2. A more dynamic and recommended approach would be to fallback on auto routing capabilities of spring-cloud function's in AWS environment. 
+Basically every time you have more then one function in your configuration, the framework will bind 
+[Routing Function](https://docs.spring.io/spring-cloud-function/docs/3.1.3/reference/html/spring-cloud-function.html#_function_routing_and_filtering) 
+as AWS Lambda, and all you need to to is provide a routing instruction via Message headers or environment variables. The instructions could themselves be very dynamic, since we support both SpEL and registering a callback interface. For more details on routing mechanisms please refer to 
+[Function Routing and Filtering](https://docs.spring.io/spring-cloud-function/docs/3.1.3/reference/html/spring-cloud-function.html#_function_routing_and_filtering) section.
+
+
 In this example we have configuration with two functions; `uppercase` and `reverse`.
 When executing from AWS Lambda functions dashboard you can simply provide one of the mentioned properties as environment variables via Configuration tab.
 For example, you can set `spring_cloud_function_routingExpression` environment variable with the value of literal; SpEL expression `'uppercase'` (not the single quotes).

spring-cloud-function-samples/function-sample-aws-routing/pom.xml

@@ -33,6 +33,10 @@
 			<groupId>org.springframework.cloud</groupId>
 			<artifactId>spring-cloud-function-adapter-aws</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+		</dependency>
 
 		<dependency>
 			<groupId>com.amazonaws</groupId>