Try to detect single-valued returns in AWS

Lambdas generally only deal with single values anyway, but for
consistency we should return similar results from a Lambda handler
as from an MVC handler in s-c-f-web.

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

@@ -1,52 +0,0 @@
-/*
- * 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.adapter.aws;
-
-import java.nio.ByteBuffer;
-import java.nio.charset.Charset;
-import java.util.Date;
-
-import com.amazonaws.services.lambda.runtime.events.KinesisEvent;
-import com.amazonaws.services.lambda.runtime.events.KinesisEvent.KinesisEventRecord;
-
-/**
- * @author Mark Fisher
- */
-public class FunctionInvokingKinesisEventHandler extends SpringBootRequestHandler<KinesisEvent, String> {
-
-	public FunctionInvokingKinesisEventHandler(Class<?> configurationClass) {
-		super(configurationClass);
-	}
-
-	@Override
-	protected String convertEvent(KinesisEvent event) {
-		StringBuilder result = new StringBuilder();
-		for (KinesisEventRecord record : event.getRecords()) {
-			String id = record.getEventID();
-			String name = record.getEventName();
-			String source = record.getEventSource();
-			Date timestamp = record.getKinesis().getApproximateArrivalTimestamp();
-			String partitionKey = record.getKinesis().getPartitionKey();
-			String sequenceNumber = record.getKinesis().getSequenceNumber();
-			ByteBuffer data = record.getKinesis().getData();
-			String dataString = new String(data.array(), Charset.forName("UTF-8"));
-			result.append(String.format("id=%s,name=%s,source=%s,timestamp=%s,partitionKey=%s,sequenceNumber=%s,data=%s",
-					id, name, source, timestamp, partitionKey, sequenceNumber, dataString));
-		}
-		return result.toString();
-	}
-}

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

@@ -16,19 +16,28 @@
 
 package org.springframework.cloud.function.adapter.aws;
 
-import com.amazonaws.services.lambda.runtime.events.S3Event;
+import java.util.List;
+
+import com.amazonaws.services.lambda.runtime.events.KinesisEvent;
+import com.amazonaws.services.lambda.runtime.events.KinesisEvent.KinesisEventRecord;
 
 /**
  * @author Mark Fisher
  */
-public class FunctionInvokingS3EventHandler extends SpringBootRequestHandler<S3Event, String> {
+public class SpringBootKinesisEventHandler
+		extends SpringBootRequestHandler<KinesisEvent, String> {
 
-	public FunctionInvokingS3EventHandler(Class<?> configurationClass) {
+	public SpringBootKinesisEventHandler() {
+		super();
+	}
+
+	public SpringBootKinesisEventHandler(Class<?> configurationClass) {
 		super(configurationClass);
 	}
 
 	@Override
-	protected String convertEvent(S3Event event) {
-		return event.toJson();
+	protected List<KinesisEventRecord> convertEvent(KinesisEvent event) {
+		// TODO: maybe convert to List<Message>
+		return event.getRecords();
 	}
 }

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

@@ -28,7 +28,7 @@ import reactor.core.publisher.Flux;
 /**
  * @author Mark Fisher
  */
-public class SpringBootRequestHandler<E, O> extends SpringFunctionInitializer implements RequestHandler<E, List<O>> {
+public class SpringBootRequestHandler<E, O> extends SpringFunctionInitializer implements RequestHandler<E, Object> {
 
 	public SpringBootRequestHandler(Class<?> configurationClass) {
 		super(configurationClass);
@@ -39,24 +39,26 @@ public class SpringBootRequestHandler<E, O> extends SpringFunctionInitializer im
 	}
 
 	@Override
-	public List<O> handleRequest(E event, Context context) {
+	public Object handleRequest(E event, Context context) {
 		initialize();
 		Object input = convertEvent(event);
 		Flux<?> output = apply(extract(input));
-		return result(output);
+		return result(input, output);
 	}
 
-	private List<O> result(Flux<?> output) {
+	private Object result(Object input, Flux<?> output) {
 		List<Object> result = new ArrayList<>();
 		for (Object value : output.toIterable()) {
 			result.add(value);
 		}
-		return convertResult(result);
+		if (isSingleValue(input) && result.size()==1) {
+			return result.get(0);
+		}
+		return result;
 	}
 
-	@SuppressWarnings("unchecked")
-	protected List<O> convertResult(List<Object> value) {
-		return (List<O>) value;
+	private boolean isSingleValue(Object input) {
+		return !(input instanceof Collection);
 	}
 
 	private Flux<?> extract(Object input) {

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

@@ -54,17 +54,24 @@ public class SpringBootStreamHandler extends SpringFunctionInitializer
 		initialize();
 		Object value = convertStream(input);
 		Flux<?> flux = apply(extract(value));
-		mapper.writeValue(output, result(flux));
+		mapper.writeValue(output, result(value, flux));
 	}
 
-	private Object result(Flux<?> flux) {
+	private Object result(Object input, Flux<?> flux) {
 		List<Object> result = new ArrayList<>();
 		for (Object value : flux.toIterable()) {
 			result.add(value);
 		}
+		if (isSingleValue(input) && result.size()==1) {
+			return result.get(0);
+		}
 		return result;
 	}
 
+	private boolean isSingleValue(Object input) {
+		return !(input instanceof Collection);
+	}
+
 	private Flux<?> extract(Object input) {
 		if (input instanceof Collection) {
 			return Flux.fromIterable((Iterable<?>) input);