GH-274 Fixed empty body request handling

Resolves #274

spring-cloud-function-web/src/main/java/org/springframework/cloud/function/web/RequestProcessor.java

@@ -64,7 +64,6 @@ import org.springframework.messaging.Message;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.util.ReflectionUtils;
-import org.springframework.util.StringUtils;
 import org.springframework.web.server.ServerWebExchange;
 import org.springframework.web.server.ServerWebInputException;
 import org.springframework.web.server.UnsupportedMediaTypeStatusException;
@@ -130,10 +129,10 @@ public class RequestProcessor {
 		Class<?> inputType = this.inspector.getInputType(function);
 		Type itemType = getItemType(function);
 
-		Object input = body;
+		Object input = body == null && inputType.isAssignableFrom(String.class) ? "" : body;
 
-		if (StringUtils.hasText(body)) {
-			if (this.shouldUseJsonConversion(body, wrapper.headers.getContentType())) {
+		if (input != null) {
+			if (this.shouldUseJsonConversion((String) input, wrapper.headers.getContentType())) {
 				Type jsonType = body.startsWith("[")
 						&& Collection.class.isAssignableFrom(inputType)
 						|| body.startsWith("{") ? inputType : Collection.class;
@@ -141,10 +140,10 @@ public class RequestProcessor {
 					jsonType = ResolvableType.forClassWithGenerics((Class<?>) jsonType,
 							(Class<?>) itemType).getType();
 				}
-				input = this.mapper.toObject(body, jsonType);
+				input = this.mapper.toObject((String) input, jsonType);
 			}
 			else {
-				input = this.converter.convert(function, body);
+				input = this.converter.convert(function, (String) input);
 			}
 		}
 

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

@@ -0,0 +1,77 @@
+/*
+ * 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
+ *
+ *      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.web.function;
+
+import java.net.URI;
+import java.util.function.Function;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.context.annotation.Bean;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.util.SocketUtils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ *
+ * @author Oleg Zhurakousky
+ * @since 2.1
+ *
+ */
+public class UserSubmittedTests {
+
+	@Before
+	public void init() throws Exception {
+		String port = "" + SocketUtils.findAvailableTcpPort();
+		System.setProperty("server.port", port);
+	}
+
+	@After
+	public void close() throws Exception {
+		System.clearProperty("server.port");
+	}
+
+	@Test
+	public void testIssue274() throws Exception {
+		SpringApplication.run(Issue274Configuration.class);
+		TestRestTemplate testRestTemplate = new TestRestTemplate();
+		String port = System.getProperty("server.port");
+		Thread.sleep(200);
+		ResponseEntity<String> response = testRestTemplate
+				.postForEntity(new URI("http://localhost:" + port + "/echo"), "", String.class);
+		assertThat(response.getBody()).isNull();
+		assertThat(response.getStatusCode()).isEqualTo(HttpStatus.OK);
+	}
+
+
+	@SpringBootApplication
+	protected static class Issue274Configuration {
+
+		@Bean
+		public Function<String, String> echo() {
+			return s -> s.toUpperCase();
+		}
+	}
+
+}