@RequestBody supports java.util.Optional

Issue: SPR-15007
(cherry picked from commit eeb7ae5)

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/AbstractMessageConverterMethodArgumentResolver.java

@@ -22,10 +22,12 @@ import java.io.PushbackInputStream;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Type;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.EnumSet;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Optional;
 import java.util.Set;
 import javax.servlet.http.HttpServletRequest;
 
@@ -45,6 +47,7 @@ import org.springframework.http.converter.GenericHttpMessageConverter;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.http.converter.HttpMessageNotReadableException;
 import org.springframework.http.server.ServletServerHttpRequest;
+import org.springframework.lang.UsesJava8;
 import org.springframework.util.Assert;
 import org.springframework.validation.Errors;
 import org.springframework.validation.annotation.Validated;
@@ -59,6 +62,7 @@ import org.springframework.web.method.support.HandlerMethodArgumentResolver;
  *
  * @author Arjen Poutsma
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  * @since 3.1
  */
 public abstract class AbstractMessageConverterMethodArgumentResolver implements HandlerMethodArgumentResolver {
@@ -128,17 +132,17 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 	 * reading from the given request.
 	 * @param <T> the expected type of the argument value to be created
 	 * @param webRequest the current request
-	 * @param methodParam the method argument
+	 * @param parameter the method parameter descriptor (may be {@code null})
 	 * @param paramType the type of the argument value to be created
 	 * @return the created method argument value
 	 * @throws IOException if the reading from the request fails
 	 * @throws HttpMediaTypeNotSupportedException if no suitable message converter is found
 	 */
-	protected <T> Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter methodParam,
+	protected <T> Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter parameter,
 			Type paramType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {
 
 		HttpInputMessage inputMessage = createInputMessage(webRequest);
-		return readWithMessageConverters(inputMessage, methodParam, paramType);
+		return readWithMessageConverters(inputMessage, parameter, paramType);
 	}
 
 	/**
@@ -146,7 +150,7 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 	 * from the given HttpInputMessage.
 	 * @param <T> the expected type of the argument value to be created
 	 * @param inputMessage the HTTP input message representing the current request
-	 * @param param the method parameter descriptor (may be {@code null})
+	 * @param parameter the method parameter descriptor (may be {@code null})
 	 * @param targetType the target type, not necessarily the same as the method
 	 * parameter type, e.g. for {@code HttpEntity<String>}.
 	 * @return the created method argument value
@@ -154,7 +158,7 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 	 * @throws HttpMediaTypeNotSupportedException if no suitable message converter is found
 	 */
 	@SuppressWarnings("unchecked")
-	protected <T> Object readWithMessageConverters(HttpInputMessage inputMessage, MethodParameter param,
+	protected <T> Object readWithMessageConverters(HttpInputMessage inputMessage, MethodParameter parameter,
 			Type targetType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {
 
 		MediaType contentType;
@@ -170,11 +174,11 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 			contentType = MediaType.APPLICATION_OCTET_STREAM;
 		}
 
-		Class<?> contextClass = (param != null ? param.getContainingClass() : null);
+		Class<?> contextClass = (parameter != null ? parameter.getContainingClass() : null);
 		Class<T> targetClass = (targetType instanceof Class ? (Class<T>) targetType : null);
 		if (targetClass == null) {
-			ResolvableType resolvableType = (param != null ?
-					ResolvableType.forMethodParameter(param) : ResolvableType.forType(targetType));
+			ResolvableType resolvableType = (parameter != null ?
+					ResolvableType.forMethodParameter(parameter) : ResolvableType.forType(targetType));
 			targetClass = (Class<T>) resolvableType.resolve();
 		}
 
@@ -193,13 +197,12 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 							logger.debug("Read [" + targetType + "] as \"" + contentType + "\" with [" + converter + "]");
 						}
 						if (inputMessage.getBody() != null) {
-							inputMessage = getAdvice().beforeBodyRead(inputMessage, param, targetType, converterType);
+							inputMessage = getAdvice().beforeBodyRead(inputMessage, parameter, targetType, converterType);
 							body = genericConverter.read(targetType, contextClass, inputMessage);
-							body = getAdvice().afterBodyRead(body, inputMessage, param, targetType, converterType);
+							body = getAdvice().afterBodyRead(body, inputMessage, parameter, targetType, converterType);
 						}
 						else {
-							body = null;
-							body = getAdvice().handleEmptyBody(body, inputMessage, param, targetType, converterType);
+							body = getAdvice().handleEmptyBody(null, inputMessage, parameter, targetType, converterType);
 						}
 						break;
 					}
@@ -210,13 +213,12 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 							logger.debug("Read [" + targetType + "] as \"" + contentType + "\" with [" + converter + "]");
 						}
 						if (inputMessage.getBody() != null) {
-							inputMessage = getAdvice().beforeBodyRead(inputMessage, param, targetType, converterType);
+							inputMessage = getAdvice().beforeBodyRead(inputMessage, parameter, targetType, converterType);
 							body = ((HttpMessageConverter<T>) converter).read(targetClass, inputMessage);
-							body = getAdvice().afterBodyRead(body, inputMessage, param, targetType, converterType);
+							body = getAdvice().afterBodyRead(body, inputMessage, parameter, targetType, converterType);
 						}
 						else {
-							body = null;
-							body = getAdvice().handleEmptyBody(body, inputMessage, param, targetType, converterType);
+							body = getAdvice().handleEmptyBody(null, inputMessage, parameter, targetType, converterType);
 						}
 						break;
 					}
@@ -254,12 +256,12 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 	 * Spring's {@link org.springframework.validation.annotation.Validated},
 	 * and custom annotations whose name starts with "Valid".
 	 * @param binder the DataBinder to be used
-	 * @param methodParam the method parameter
-	 * @see #isBindExceptionRequired
+	 * @param parameter the method parameter descriptor
 	 * @since 4.1.5
+	 * @see #isBindExceptionRequired
 	 */
-	protected void validateIfApplicable(WebDataBinder binder, MethodParameter methodParam) {
-		Annotation[] annotations = methodParam.getParameterAnnotations();
+	protected void validateIfApplicable(WebDataBinder binder, MethodParameter parameter) {
+		Annotation[] annotations = parameter.getParameterAnnotations();
 		for (Annotation ann : annotations) {
 			Validated validatedAnn = AnnotationUtils.getAnnotation(ann, Validated.class);
 			if (validatedAnn != null || ann.annotationType().getSimpleName().startsWith("Valid")) {
@@ -274,17 +276,28 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 	/**
 	 * Whether to raise a fatal bind exception on validation errors.
 	 * @param binder the data binder used to perform data binding
-	 * @param methodParam the method argument
+	 * @param parameter the method parameter descriptor
 	 * @return {@code true} if the next method argument is not of type {@link Errors}
 	 * @since 4.1.5
 	 */
-	protected boolean isBindExceptionRequired(WebDataBinder binder, MethodParameter methodParam) {
-		int i = methodParam.getParameterIndex();
-		Class<?>[] paramTypes = methodParam.getMethod().getParameterTypes();
+	protected boolean isBindExceptionRequired(WebDataBinder binder, MethodParameter parameter) {
+		int i = parameter.getParameterIndex();
+		Class<?>[] paramTypes = parameter.getMethod().getParameterTypes();
 		boolean hasBindingResult = (paramTypes.length > (i + 1) && Errors.class.isAssignableFrom(paramTypes[i + 1]));
 		return !hasBindingResult;
 	}
 
+	/**
+	 * Adapt the given argument against the method parameter, if necessary.
+	 * @param arg the resolved argument
+	 * @param parameter the method parameter descriptor
+	 * @return the adapted argument, or the original resolved argument as-is
+	 * @since 4.3.5
+	 */
+	protected Object adaptArgumentIfNecessary(Object arg, MethodParameter parameter) {
+		return (parameter.isOptional() ? OptionalResolver.resolveValue(arg) : arg);
+	}
+
 
 	private static class EmptyBodyCheckingHttpInputMessage implements HttpInputMessage {
 
@@ -335,4 +348,20 @@ public abstract class AbstractMessageConverterMethodArgumentResolver implements
 		}
 	}
 
+
+	/**
+	 * Inner class to avoid hard-coded dependency on Java 8 Optional type...
+	 */
+	@UsesJava8
+	private static class OptionalResolver {
+
+		public static Object resolveValue(Object value) {
+			if (value == null || (value instanceof Collection && ((Collection) value).isEmpty()) ||
+					(value instanceof Object[] && ((Object[]) value).length == 0)) {
+				return Optional.empty();
+			}
+			return Optional.of(value);
+		}
+	}
+
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestPartMethodArgumentResolver.java

@@ -16,15 +16,12 @@
 
 package org.springframework.web.servlet.mvc.method.annotation;
 
-import java.util.Collection;
 import java.util.List;
-import java.util.Optional;
 import javax.servlet.http.HttpServletRequest;
 
 import org.springframework.core.MethodParameter;
 import org.springframework.http.HttpInputMessage;
 import org.springframework.http.converter.HttpMessageConverter;
-import org.springframework.lang.UsesJava8;
 import org.springframework.validation.BindingResult;
 import org.springframework.web.bind.MethodArgumentNotValidException;
 import org.springframework.web.bind.WebDataBinder;
@@ -157,11 +154,7 @@ public class RequestPartMethodArgumentResolver extends AbstractMessageConverterM
 				throw new MissingServletRequestPartException(name);
 			}
 		}
-		if (parameter.isOptional()) {
-			arg = OptionalResolver.resolveValue(arg);
-		}
-
-		return arg;
+		return adaptArgumentIfNecessary(arg, parameter);
 	}
 
 	private String getPartName(MethodParameter methodParam, RequestPart requestPart) {
@@ -177,20 +170,4 @@ public class RequestPartMethodArgumentResolver extends AbstractMessageConverterM
 		return partName;
 	}
 
-
-	/**
-	 * Inner class to avoid hard-coded dependency on Java 8 Optional type...
-	 */
-	@UsesJava8
-	private static class OptionalResolver {
-
-		public static Object resolveValue(Object value) {
-			if (value == null || (value instanceof Collection && ((Collection) value).isEmpty()) ||
-					(value instanceof Object[] && ((Object[]) value).length == 0)) {
-				return Optional.empty();
-			}
-			return Optional.of(value);
-		}
-	}
-
 }

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestResponseBodyMethodProcessor.java

@@ -19,7 +19,6 @@ package org.springframework.web.servlet.mvc.method.annotation;
 import java.io.IOException;
 import java.lang.reflect.Type;
 import java.util.List;
-
 import javax.servlet.http.HttpServletRequest;
 
 import org.springframework.core.Conventions;
@@ -55,6 +54,7 @@ import org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolv
  *
  * @author Arjen Poutsma
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  * @since 3.1
  */
 public class RequestResponseBodyMethodProcessor extends AbstractMessageConverterMethodProcessor {
@@ -124,7 +124,8 @@ public class RequestResponseBodyMethodProcessor extends AbstractMessageConverter
 	public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
 			NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
 
-		Object arg = readWithMessageConverters(webRequest, parameter, parameter.getGenericParameterType());
+		parameter = parameter.nestedIfOptional();
+		Object arg = readWithMessageConverters(webRequest, parameter, parameter.getNestedGenericParameterType());
 		String name = Conventions.getVariableNameForParameter(parameter);
 
 		WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
@@ -136,28 +137,28 @@ public class RequestResponseBodyMethodProcessor extends AbstractMessageConverter
 		}
 		mavContainer.addAttribute(BindingResult.MODEL_KEY_PREFIX + name, binder.getBindingResult());
 
-		return arg;
+		return adaptArgumentIfNecessary(arg, parameter);
 	}
 
 	@Override
-	protected <T> Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter methodParam,
+	protected <T> Object readWithMessageConverters(NativeWebRequest webRequest, MethodParameter parameter,
 			Type paramType) throws IOException, HttpMediaTypeNotSupportedException, HttpMessageNotReadableException {
 
 		HttpServletRequest servletRequest = webRequest.getNativeRequest(HttpServletRequest.class);
 		ServletServerHttpRequest inputMessage = new ServletServerHttpRequest(servletRequest);
 
-		Object arg = readWithMessageConverters(inputMessage, methodParam, paramType);
+		Object arg = readWithMessageConverters(inputMessage, parameter, paramType);
 		if (arg == null) {
-			if (checkRequired(methodParam)) {
+			if (checkRequired(parameter)) {
 				throw new HttpMessageNotReadableException("Required request body is missing: " +
-						methodParam.getMethod().toGenericString());
+						parameter.getMethod().toGenericString());
 			}
 		}
 		return arg;
 	}
 
-	protected boolean checkRequired(MethodParameter methodParam) {
-		return methodParam.getParameterAnnotation(RequestBody.class).required();
+	protected boolean checkRequired(MethodParameter parameter) {
+		return (parameter.getParameterAnnotation(RequestBody.class).required() && !parameter.isOptional());
 	}
 
 	@Override

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/RequestResponseBodyMethodProcessorMockTests.java

@@ -16,15 +16,12 @@
 
 package org.springframework.web.servlet.mvc.method.annotation;
 
-import static org.junit.Assert.*;
-import static org.mockito.BDDMockito.*;
-
 import java.lang.reflect.Method;
-import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
-
+import java.util.Optional;
 import javax.validation.Valid;
 import javax.validation.constraints.NotNull;
 
@@ -54,6 +51,9 @@ import org.springframework.web.context.request.ServletWebRequest;
 import org.springframework.web.method.support.ModelAndViewContainer;
 import org.springframework.web.servlet.HandlerMapping;
 
+import static org.junit.Assert.*;
+import static org.mockito.BDDMockito.*;
+
 /**
  * Test fixture for {@link RequestResponseBodyMethodProcessor} delegating to a
  * mock HttpMessageConverter.
@@ -62,6 +62,7 @@ import org.springframework.web.servlet.HandlerMapping;
  *
  * @author Arjen Poutsma
  * @author Rossen Stoyanchev
+ * @author Juergen Hoeller
  */
 public class RequestResponseBodyMethodProcessorMockTests {
 
@@ -75,6 +76,7 @@ public class RequestResponseBodyMethodProcessorMockTests {
 	private MethodParameter paramInt;
 	private MethodParameter paramValidBean;
 	private MethodParameter paramStringNotRequired;
+	private MethodParameter paramOptionalString;
 	private MethodParameter returnTypeString;
 	private MethodParameter returnTypeInt;
 	private MethodParameter returnTypeStringProduces;
@@ -103,12 +105,13 @@ public class RequestResponseBodyMethodProcessorMockTests {
 		Method methodHandle1 = getClass().getMethod("handle1", String.class, Integer.TYPE);
 		paramRequestBodyString = new MethodParameter(methodHandle1, 0);
 		paramInt = new MethodParameter(methodHandle1, 1);
+		paramValidBean = new MethodParameter(getClass().getMethod("handle2", SimpleBean.class), 0);
+		paramStringNotRequired = new MethodParameter(getClass().getMethod("handle3", String.class), 0);
+		paramOptionalString = new MethodParameter(getClass().getMethod("handle4", Optional.class), 0);
 		returnTypeString = new MethodParameter(methodHandle1, -1);
-		returnTypeInt = new MethodParameter(getClass().getMethod("handle2"), -1);
-		returnTypeStringProduces = new MethodParameter(getClass().getMethod("handle3"), -1);
-		returnTypeResource = new MethodParameter(getClass().getMethod("handle6"), -1);
-		paramValidBean = new MethodParameter(getClass().getMethod("handle4", SimpleBean.class), 0);
-		paramStringNotRequired = new MethodParameter(getClass().getMethod("handle5", String.class), 0);
+		returnTypeInt = new MethodParameter(getClass().getMethod("handle5"), -1);
+		returnTypeStringProduces = new MethodParameter(getClass().getMethod("handle6"), -1);
+		returnTypeResource = new MethodParameter(getClass().getMethod("handle7"), -1);
 
 		mavContainer = new ModelAndViewContainer();
 
@@ -136,7 +139,7 @@ public class RequestResponseBodyMethodProcessorMockTests {
 		servletRequest.addHeader("Content-Type", contentType.toString());
 
 		String body = "Foo";
-		servletRequest.setContent(body.getBytes(Charset.forName("UTF-8")));
+		servletRequest.setContent(body.getBytes(StandardCharsets.UTF_8));
 
 		given(stringMessageConverter.canRead(String.class, contentType)).willReturn(true);
 		given(stringMessageConverter.read(eq(String.class), isA(HttpInputMessage.class))).willReturn(body);
@@ -168,7 +171,7 @@ public class RequestResponseBodyMethodProcessorMockTests {
 	private void testResolveArgumentWithValidation(SimpleBean simpleBean) throws Exception {
 		MediaType contentType = MediaType.TEXT_PLAIN;
 		servletRequest.addHeader("Content-Type", contentType.toString());
-		servletRequest.setContent("payload".getBytes(Charset.forName("UTF-8")));
+		servletRequest.setContent("payload".getBytes(StandardCharsets.UTF_8));
 
 		@SuppressWarnings("unchecked")
 		HttpMessageConverter<SimpleBean> beanConverter = mock(HttpMessageConverter.class);
@@ -184,7 +187,7 @@ public class RequestResponseBodyMethodProcessorMockTests {
 	public void resolveArgumentCannotRead() throws Exception {
 		MediaType contentType = MediaType.TEXT_PLAIN;
 		servletRequest.addHeader("Content-Type", contentType.toString());
-		servletRequest.setContent("payload".getBytes(Charset.forName("UTF-8")));
+		servletRequest.setContent("payload".getBytes(StandardCharsets.UTF_8));
 
 		given(stringMessageConverter.canRead(String.class, contentType)).willReturn(false);
 
@@ -193,7 +196,7 @@ public class RequestResponseBodyMethodProcessorMockTests {
 
 	@Test(expected = HttpMediaTypeNotSupportedException.class)
 	public void resolveArgumentNoContentType() throws Exception {
-		servletRequest.setContent("payload".getBytes(Charset.forName("UTF-8")));
+		servletRequest.setContent("payload".getBytes(StandardCharsets.UTF_8));
 		given(stringMessageConverter.canRead(String.class, MediaType.APPLICATION_OCTET_STREAM)).willReturn(false);
 		processor.resolveArgument(paramRequestBodyString, mavContainer, webRequest, null);
 	}
@@ -201,13 +204,11 @@ public class RequestResponseBodyMethodProcessorMockTests {
 	@Test(expected = HttpMediaTypeNotSupportedException.class)
 	public void resolveArgumentInvalidContentType() throws Exception {
 		this.servletRequest.setContentType("bad");
-		servletRequest.setContent("payload".getBytes(Charset.forName("UTF-8")));
+		servletRequest.setContent("payload".getBytes(StandardCharsets.UTF_8));
 		processor.resolveArgument(paramRequestBodyString, mavContainer, webRequest, null);
 	}
 
-	// SPR-9942
-
-	@Test(expected = HttpMessageNotReadableException.class)
+	@Test(expected = HttpMessageNotReadableException.class)  // SPR-9942
 	public void resolveArgumentRequiredNoContent() throws Exception {
 		servletRequest.setContentType(MediaType.TEXT_PLAIN_VALUE);
 		servletRequest.setContent(new byte[0]);
@@ -216,6 +217,23 @@ public class RequestResponseBodyMethodProcessorMockTests {
 		assertNull(processor.resolveArgument(paramRequestBodyString, mavContainer, webRequest, new ValidatingBinderFactory()));
 	}
 
+	@Test
+	public void resolveArgumentNotGetRequests() throws Exception {
+		servletRequest.setMethod("GET");
+		servletRequest.setContent(new byte[0]);
+		given(stringMessageConverter.canRead(String.class, MediaType.APPLICATION_OCTET_STREAM)).willReturn(false);
+		assertNull(processor.resolveArgument(paramStringNotRequired, mavContainer, webRequest, new ValidatingBinderFactory()));
+	}
+
+	@Test
+	public void resolveArgumentNotRequiredWithContent() throws Exception {
+		servletRequest.setContentType("text/plain");
+		servletRequest.setContent("body".getBytes());
+		given(stringMessageConverter.canRead(String.class, MediaType.TEXT_PLAIN)).willReturn(true);
+		given(stringMessageConverter.read(eq(String.class), isA(HttpInputMessage.class))).willReturn("body");
+		assertEquals("body", processor.resolveArgument(paramStringNotRequired, mavContainer, webRequest, new ValidatingBinderFactory()));
+	}
+
 	@Test
 	public void resolveArgumentNotRequiredNoContent() throws Exception {
 		servletRequest.setContentType("text/plain");
@@ -224,8 +242,7 @@ public class RequestResponseBodyMethodProcessorMockTests {
 		assertNull(processor.resolveArgument(paramStringNotRequired, mavContainer, webRequest, new ValidatingBinderFactory()));
 	}
 
-	// SPR-13417
-	@Test
+	@Test  // SPR-13417
 	public void resolveArgumentNotRequiredNoContentNoContentType() throws Exception {
 		servletRequest.setContent(new byte[0]);
 		given(stringMessageConverter.canRead(String.class, MediaType.TEXT_PLAIN)).willReturn(true);
@@ -234,11 +251,28 @@ public class RequestResponseBodyMethodProcessorMockTests {
 	}
 
 	@Test
-	public void resolveArgumentNotGetRequests() throws Exception {
-		servletRequest.setMethod("GET");
+	public void resolveArgumentOptionalWithContent() throws Exception {
+		servletRequest.setContentType("text/plain");
+		servletRequest.setContent("body".getBytes());
+		given(stringMessageConverter.canRead(String.class, MediaType.TEXT_PLAIN)).willReturn(true);
+		given(stringMessageConverter.read(eq(String.class), isA(HttpInputMessage.class))).willReturn("body");
+		assertEquals(Optional.of("body"), processor.resolveArgument(paramOptionalString, mavContainer, webRequest, new ValidatingBinderFactory()));
+	}
+
+	@Test
+	public void resolveArgumentOptionalNoContent() throws Exception {
+		servletRequest.setContentType("text/plain");
 		servletRequest.setContent(new byte[0]);
+		given(stringMessageConverter.canRead(String.class, MediaType.TEXT_PLAIN)).willReturn(true);
+		assertEquals(Optional.empty(), processor.resolveArgument(paramOptionalString, mavContainer, webRequest, new ValidatingBinderFactory()));
+	}
+
+	@Test
+	public void resolveArgumentOptionalNoContentNoContentType() throws Exception {
+		servletRequest.setContent(new byte[0]);
+		given(stringMessageConverter.canRead(String.class, MediaType.TEXT_PLAIN)).willReturn(true);
 		given(stringMessageConverter.canRead(String.class, MediaType.APPLICATION_OCTET_STREAM)).willReturn(false);
-		assertNull(processor.resolveArgument(paramStringNotRequired, mavContainer, webRequest, new ValidatingBinderFactory()));
+		assertEquals(Optional.empty(), processor.resolveArgument(paramOptionalString, mavContainer, webRequest, new ValidatingBinderFactory()));
 	}
 
 	@Test
@@ -299,7 +333,7 @@ public class RequestResponseBodyMethodProcessorMockTests {
 
 	@Test
 	public void handleReturnTypeResource() throws Exception {
-		Resource returnValue = new ByteArrayResource("Content".getBytes(Charset.forName("UTF-8")));
+		Resource returnValue = new ByteArrayResource("Content".getBytes(StandardCharsets.UTF_8));
 
 		given(resourceMessageConverter.canWrite(ByteArrayResource.class, null)).willReturn(true);
 		given(resourceMessageConverter.getSupportedMediaTypes()).willReturn(Collections.singletonList(MediaType.ALL));
@@ -312,9 +346,7 @@ public class RequestResponseBodyMethodProcessorMockTests {
 		assertEquals(200, servletResponse.getStatus());
 	}
 
-	// SPR-9841
-
-	@Test
+	@Test  // SPR-9841
 	public void handleReturnValueMediaTypeSuffix() throws Exception {
 		String body = "Foo";
 		MediaType accepted = MediaType.APPLICATION_XHTML_XML;
@@ -340,29 +372,37 @@ public class RequestResponseBodyMethodProcessorMockTests {
 	}
 
 	@SuppressWarnings("unused")
-	public int handle2() {
-		return 42;
+	public void handle2(@Valid @RequestBody SimpleBean b) {
 	}
 
 	@SuppressWarnings("unused")
-	@ResponseBody
-	public String handle3() {
-		return null;
+	public void handle3(@RequestBody(required = false) String s) {
 	}
 
 	@SuppressWarnings("unused")
-	public void handle4(@Valid @RequestBody SimpleBean b) {
+	public void handle4(@RequestBody Optional<String> s) {
 	}
 
 	@SuppressWarnings("unused")
-	public void handle5(@RequestBody(required=false) String s) {
+	public int handle5() {
+		return 42;
 	}
 
 	@SuppressWarnings("unused")
 	@ResponseBody
-	public Resource handle6() {return null;}
+	public String handle6() {
+		return null;
+	}
+
+	@SuppressWarnings("unused")
+	@ResponseBody
+	public Resource handle7() {
+		return null;
+	}
+
 
 	private final class ValidatingBinderFactory implements WebDataBinderFactory {
+
 		@Override
 		public WebDataBinder createBinder(NativeWebRequest webRequest, Object target, String objectName) throws Exception {
 			LocalValidatorFactoryBean validator = new LocalValidatorFactoryBean();
@@ -373,6 +413,7 @@ public class RequestResponseBodyMethodProcessorMockTests {
 		}
 	}
 
+
 	@SuppressWarnings("unused")
 	private static class SimpleBean {