Add test to vaidate defered output conversion

spring-cloud-stream/src/test/java/org/springframework/cloud/stream/function/DataFlowScenarioTests.java

@@ -0,0 +1,121 @@
+/*
+ * Copyright 2021-2021 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.stream.function;
+
+import java.lang.reflect.Field;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Function;
+
+import org.assertj.core.util.Arrays;
+import org.junit.Test;
+
+import org.springframework.boot.WebApplicationType;
+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.catalog.SimpleFunctionRegistry.FunctionInvocationWrapper;
+import org.springframework.cloud.stream.binder.ProducerProperties;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.expression.Expression;
+import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageHeaders;
+import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.util.MimeTypeUtils;
+import org.springframework.util.ReflectionUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class DataFlowScenarioTests {
+
+	private ApplicationContext context;
+
+
+	private FunctionCatalog configureCatalog(Class<?>... configClass) {
+		this.context = new SpringApplicationBuilder(configClass)
+				.web(WebApplicationType.NONE)
+				.run("--logging.level.org.springframework.cloud.function=DEBUG",
+						"--spring.main.lazy-initialization=true");
+		FunctionCatalog catalog = context.getBean(FunctionCatalog.class);
+		return catalog;
+	}
+
+	@Test
+	public void dfAppsTest() throws Exception {
+		FunctionCatalog catalog = this.configureCatalog(DFConfiguration.class);
+
+		FunctionInvocationWrapper function = catalog.lookup("byteArrayToString|splitterFunction", "text/plain");
+		ProducerProperties producerProperties = new ProducerProperties();
+		SpelExpressionParser parser = new SpelExpressionParser();
+		Expression expression = parser.parseExpression("payload");
+		producerProperties.setPartitionKeyExpression(expression);
+		PartitionAwareFunctionWrapper wrapper = new PartitionAwareFunctionWrapper(function, (ConfigurableApplicationContext) context, producerProperties);
+		Field f = ReflectionUtils.findField(PartitionAwareFunctionWrapper.class, "outputMessageEnricher");
+		f.setAccessible(true);
+		AtomicInteger i = new AtomicInteger();
+		Function<Message, Message> enricher = message -> {
+			i.incrementAndGet();
+			assertThat(message.getPayload()).isInstanceOf(String.class);
+			return message;
+		};
+		f.set(wrapper, enricher);
+		wrapper.apply(MessageBuilder.withPayload("foo bar baz".getBytes())
+						.setHeader(MessageHeaders.CONTENT_TYPE, "text/plain")
+						.build());
+		assertThat(i.get()).isEqualTo(3);
+	}
+
+	@EnableAutoConfiguration
+	public static class DFConfiguration {
+
+		@Bean
+		public Function<Message<?>, Message<?>> byteArrayToString() {
+			return message -> {
+				if (message.getPayload() instanceof byte[]) {
+					final MessageHeaders headers = message.getHeaders();
+					String contentType = headers.containsKey(MessageHeaders.CONTENT_TYPE)
+							? headers.get(MessageHeaders.CONTENT_TYPE).toString()
+							: MimeTypeUtils.APPLICATION_JSON_VALUE;
+
+					if (contentType.contains("text") || contentType.contains("json") || contentType.contains("x-spring-tuple")) {
+						message = MessageBuilder.withPayload(new String(((byte[]) message.getPayload())))
+								.copyHeaders(message.getHeaders())
+								.build();
+					}
+				}
+
+				return message;
+			};
+		}
+
+		@Bean
+		public Function<Message<?>, List<Message<?>>> splitterFunction() {
+			return message -> {
+				List<Object> split = Arrays.asList(((String) message.getPayload()).split(" "));
+				List<Message<?>> messages = new ArrayList<>();
+				for (Object value : split) {
+					messages.add(MessageBuilder.withPayload(value).build());
+				}
+				return messages;
+			};
+		}
+	}
+}