Example implementation for Aws API Gateway

User can extend SpringBootApiGatewayRequestHandler instead of the
generic SpringBootRequestHandler. It ties the code to AWS and the
API Gateway, but at least it supports the incoming data fully.

Fixes gh-111, closes gh-136

spring-cloud-function-adapters/spring-cloud-function-adapter-aws/src/test/java/org/springframework/cloud/function/adapter/aws/SpringBootApiGatewayRequestHandlerTests.java

@@ -0,0 +1,108 @@
+package org.springframework.cloud.function.adapter.aws;
+
+import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyRequestEvent;
+import com.amazonaws.services.lambda.runtime.events.APIGatewayProxyResponseEvent;
+import org.junit.Test;
+import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
+import org.springframework.cloud.function.context.config.ContextFunctionCatalogAutoConfiguration;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.support.GenericMessage;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.function.Function;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class SpringBootApiGatewayRequestHandlerTests {
+
+	private SpringBootApiGatewayRequestHandler handler;
+
+	@Test
+	public void functionBean() {
+		handler = new SpringBootApiGatewayRequestHandler(FunctionConfig.class);
+		handler.initialize();
+
+		APIGatewayProxyRequestEvent request = new APIGatewayProxyRequestEvent();
+		request.setBody("{\"value\":\"foo\"}");
+
+		Object output = handler.handleRequest(request, null);
+		assertThat(output).isInstanceOf(APIGatewayProxyResponseEvent.class);
+		assertThat(((APIGatewayProxyResponseEvent) output).getStatusCode()).isEqualTo(200);
+		assertThat(((APIGatewayProxyResponseEvent) output).getBody()).isEqualTo("{\"value\":\"FOO\"}");
+	}
+
+	@Configuration
+	@Import({ContextFunctionCatalogAutoConfiguration.class,
+			JacksonAutoConfiguration.class})
+	protected static class FunctionConfig {
+		@Bean
+		public Function<Foo, Bar> function() {
+			return foo -> new Bar(foo.getValue().toUpperCase());
+		}
+	}
+
+	@Test
+	public void functionMessageBean() {
+		handler = new SpringBootApiGatewayRequestHandler(FunctionMessageConfig.class);
+		handler.initialize();
+
+		APIGatewayProxyRequestEvent request = new APIGatewayProxyRequestEvent();
+		request.setBody("{\"value\":\"foo\"}");
+
+		Object output = handler.handleRequest(request, null);
+		assertThat(output).isInstanceOf(APIGatewayProxyResponseEvent.class);
+		assertThat(((APIGatewayProxyResponseEvent) output).getStatusCode()).isEqualTo(200);
+		assertThat(((APIGatewayProxyResponseEvent) output).getHeaders().get("spring")).isEqualTo("cloud");
+		assertThat(((APIGatewayProxyResponseEvent) output).getBody()).isEqualTo("{\"value\":\"FOO\"}");
+	}
+
+	@Configuration
+	@Import({ContextFunctionCatalogAutoConfiguration.class,
+			JacksonAutoConfiguration.class})
+	protected static class FunctionMessageConfig {
+		@Bean
+		public Function<Message<Foo>, Message<Bar>> function() {
+			return (foo -> {
+				Map<String, Object> headers = Collections.singletonMap("spring", "cloud");
+				return new GenericMessage<>(
+						new Bar(foo.getPayload().getValue().toUpperCase()),
+						headers);
+			});
+		}
+	}
+
+	protected static class Foo {
+		private String value;
+
+		public String getValue() {
+			return value;
+		}
+
+		public void setValue(String value) {
+			this.value = value;
+		}
+	}
+
+	protected static class Bar {
+		private String value;
+
+		public Bar() {
+		}
+
+		public Bar(String value) {
+			this.value = value;
+		}
+
+		public String getValue() {
+			return value;
+		}
+
+		public void setValue(String value) {
+			this.value = value;
+		}
+	}
+}