Add required flag to @RequestBody

If true and there is no body => HttpMessageNotReadableException
If false and there is no body, the argument resolves to null.

Issue: SPR-9239

spring-web/src/main/java/org/springframework/web/bind/annotation/RequestBody.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2012 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.
@@ -44,4 +44,12 @@ import org.springframework.http.converter.HttpMessageConverter;
 @Documented
 public @interface RequestBody {
 
+	/**
+	 * Whether body content is required.
+	 * <p>Default is <code>true</code>, leading to an exception thrown in case
+	 * there is no body content. Switch this to <code>false</code> if you prefer
+	 * <code>null</value> to be passed when the body content is <code>null</code>.
+	 */
+	boolean required() default true;
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2012 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.
@@ -23,9 +23,12 @@ import java.util.List;
 import org.springframework.core.Conventions;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.http.HttpInputMessage;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.HttpMessageNotReadableException;
 import org.springframework.validation.BindingResult;
 import org.springframework.web.HttpMediaTypeNotAcceptableException;
+import org.springframework.web.HttpMediaTypeNotSupportedException;
 import org.springframework.web.bind.MethodArgumentNotValidException;
 import org.springframework.web.bind.WebDataBinder;
 import org.springframework.web.bind.annotation.RequestBody;
@@ -36,17 +39,17 @@ import org.springframework.web.method.support.ModelAndViewContainer;
 import org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver;
 
 /**
- * Resolves method arguments annotated with {@code @RequestBody} and handles 
+ * Resolves method arguments annotated with {@code @RequestBody} and handles
  * return values from methods annotated with {@code @ResponseBody} by reading
- * and writing to the body of the request or response with an 
+ * and writing to the body of the request or response with an
  * {@link HttpMessageConverter}.
- * 
- * <p>An {@code @RequestBody} method argument is also validated if it is 
- * annotated with {@code @javax.validation.Valid}. In case of validation 
- * failure, {@link MethodArgumentNotValidException} is raised and results 
+ *
+ * <p>An {@code @RequestBody} method argument is also validated if it is
+ * annotated with {@code @javax.validation.Valid}. In case of validation
+ * failure, {@link MethodArgumentNotValidException} is raised and results
  * in a 400 response status code if {@link DefaultHandlerExceptionResolver}
- * is configured. 
- * 
+ * is configured.
+ *
  * @author Arjen Poutsma
  * @author Rossen Stoyanchev
  * @since 3.1
@@ -65,24 +68,56 @@ public class RequestResponseBodyMethodProcessor extends AbstractMessageConverter
 		return returnType.getMethodAnnotation(ResponseBody.class) != null;
 	}
 
+	/**
+	 * {@inheritDoc}
+	 * @throws MethodArgumentNotValidException if validation fails
+	 * @throws HttpMessageNotReadableException if {@link RequestBody#required()}
+	 * 	is {@code true} and there is no body content or if there is no suitable
+	 * 	converter to read the content with.
+	 */
 	public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
 			NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
 
 		Object arg = readWithMessageConverters(webRequest, parameter, parameter.getParameterType());
+		validate(parameter, webRequest, binderFactory, arg);
+		return arg;
+	}
+
+	private void validate(MethodParameter parameter, NativeWebRequest webRequest,
+			WebDataBinderFactory binderFactory, Object arg) throws Exception, MethodArgumentNotValidException {
+
+		if (arg == null) {
+			return;
+		}
 		Annotation[] annotations = parameter.getParameterAnnotations();
 		for (Annotation annot : annotations) {
-			if (annot.annotationType().getSimpleName().startsWith("Valid")) {
-				String name = Conventions.getVariableNameForParameter(parameter);
-				WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
-				Object hints = AnnotationUtils.getValue(annot);
-				binder.validate(hints instanceof Object[] ? (Object[]) hints : new Object[] {hints});
-				BindingResult bindingResult = binder.getBindingResult();
-				if (bindingResult.hasErrors()) {
-					throw new MethodArgumentNotValidException(parameter, bindingResult);
-				}
+			if (!annot.annotationType().getSimpleName().startsWith("Valid")) {
+				continue;
+			}
+			String name = Conventions.getVariableNameForParameter(parameter);
+			WebDataBinder binder = binderFactory.createBinder(webRequest, arg, name);
+			Object hints = AnnotationUtils.getValue(annot);
+			binder.validate(hints instanceof Object[] ? (Object[]) hints : new Object[] {hints});
+			BindingResult bindingResult = binder.getBindingResult();
+			if (bindingResult.hasErrors()) {
+				throw new MethodArgumentNotValidException(parameter, bindingResult);
 			}
 		}
-		return arg;
+	}
+
+	@Override
+	protected <T> Object readWithMessageConverters(HttpInputMessage inputMessage,
+			MethodParameter methodParam, Class<T> paramType) throws IOException, HttpMediaTypeNotSupportedException {
+
+		if (inputMessage.getBody() != null) {
+			return super.readWithMessageConverters(inputMessage, methodParam, paramType);
+		}
+
+		RequestBody annot = methodParam.getParameterAnnotation(RequestBody.class);
+		if (!annot.required()) {
+			return null;
+		}
+		throw new HttpMessageNotReadableException("Required request body content is missing: " + methodParam.toString());
 	}
 
 	public void handleReturnValue(Object returnValue, MethodParameter returnType,

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2012 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.
@@ -26,6 +26,7 @@ import static org.easymock.EasyMock.verify;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
@@ -47,6 +48,7 @@ import org.springframework.http.HttpOutputMessage;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.ByteArrayHttpMessageConverter;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.HttpMessageNotReadableException;
 import org.springframework.http.converter.StringHttpMessageConverter;
 import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
 import org.springframework.mock.web.MockHttpServletRequest;
@@ -79,6 +81,7 @@ public class RequestResponseBodyMethodProcessorTests {
 	private MethodParameter paramRequestBodyString;
 	private MethodParameter paramInt;
 	private MethodParameter paramValidBean;
+	private MethodParameter paramStringNotRequired;
 	private MethodParameter returnTypeString;
 	private MethodParameter returnTypeInt;
 	private MethodParameter returnTypeStringProduces;
@@ -108,6 +111,7 @@ public class RequestResponseBodyMethodProcessorTests {
 		returnTypeInt = new MethodParameter(getClass().getMethod("handle2"), -1);
 		returnTypeStringProduces = new MethodParameter(getClass().getMethod("handle3"), -1);
 		paramValidBean = new MethodParameter(getClass().getMethod("handle4", SimpleBean.class), 0);
+		paramStringNotRequired = new MethodParameter(getClass().getMethod("handle5", String.class), 0);
 
 		mavContainer = new ModelAndViewContainer();
 
@@ -134,6 +138,8 @@ public class RequestResponseBodyMethodProcessorTests {
 		servletRequest.addHeader("Content-Type", contentType.toString());
 
 		String body = "Foo";
+		servletRequest.setContent(body.getBytes());
+
 		expect(messageConverter.canRead(String.class, contentType)).andReturn(true);
 		expect(messageConverter.read(eq(String.class), isA(HttpInputMessage.class))).andReturn(body);
 		replay(messageConverter);
@@ -165,6 +171,7 @@ public class RequestResponseBodyMethodProcessorTests {
 	private void testResolveArgumentWithValidation(SimpleBean simpleBean) throws IOException, Exception {
 		MediaType contentType = MediaType.TEXT_PLAIN;
 		servletRequest.addHeader("Content-Type", contentType.toString());
+		servletRequest.setContent(new byte[] {});
 
 		@SuppressWarnings("unchecked")
 		HttpMessageConverter<SimpleBean> beanConverter = createMock(HttpMessageConverter.class);
@@ -183,6 +190,7 @@ public class RequestResponseBodyMethodProcessorTests {
 	public void resolveArgumentNotReadable() throws Exception {
 		MediaType contentType = MediaType.TEXT_PLAIN;
 		servletRequest.addHeader("Content-Type", contentType.toString());
+		servletRequest.setContent(new byte[] {});
 
 		expect(messageConverter.canRead(String.class, contentType)).andReturn(false);
 		replay(messageConverter);
@@ -194,10 +202,22 @@ public class RequestResponseBodyMethodProcessorTests {
 
 	@Test(expected = HttpMediaTypeNotSupportedException.class)
 	public void resolveArgumentNoContentType() throws Exception {
+		servletRequest.setContent(new byte[] {});
+		processor.resolveArgument(paramRequestBodyString, mavContainer, webRequest, null);
+		fail("Expected exception");
+	}
+
+	@Test(expected = HttpMessageNotReadableException.class)
+	public void resolveArgumentRequiredNoContent() throws Exception {
 		processor.resolveArgument(paramRequestBodyString, mavContainer, webRequest, null);
 		fail("Expected exception");
 	}
 
+	@Test
+	public void resolveArgumentNotRequiredNoContent() throws Exception {
+		assertNull(processor.resolveArgument(paramStringNotRequired, mavContainer, webRequest, null));
+	}
+
 	@Test
 	public void handleReturnValue() throws Exception {
 		MediaType accepted = MediaType.TEXT_PLAIN;
@@ -310,6 +330,9 @@ public class RequestResponseBodyMethodProcessorTests {
 	public void handle4(@Valid @RequestBody SimpleBean b) {
 	}
 
+	public void handle5(@RequestBody(required=false) String s) {
+	}
+
 	private final class ValidatingBinderFactory implements WebDataBinderFactory {
 		public WebDataBinder createBinder(NativeWebRequest webRequest, Object target, String objectName) throws Exception {
 			LocalValidatorFactoryBean validator = new LocalValidatorFactoryBean();

src/dist/changelog.txt

@@ -28,6 +28,7 @@ Changes in version 3.2 M1
 * add ability to configure custom MessageCodesResolver through the MVC Java config
 * add option in MappingJacksonJsonView for setting the Content-Length header
 * decode path variables when url decoding is turned off in AbstractHandlerMapping
+* add required flag to @RequestBody annotation
 
 Changes in version 3.1.1 (2012-02-16)
 -------------------------------------