@RequestParam/RequestHeader/CookieValue's defaultValue allows for declaring empty String (SPR-6791)

org.springframework.web.servlet/src/test/java/org/springframework/web/servlet/mvc/annotation/ServletAnnotationControllerTests.java

@@ -199,7 +199,7 @@ public class ServletAnnotationControllerTests {
 		MockHttpServletRequest request = new MockHttpServletRequest("GET", "/myPath.do");
 		MockHttpServletResponse response = new MockHttpServletResponse();
 		servlet.service(request, response);
-		assertEquals("foo-null-bar", response.getContentAsString());
+		assertEquals("foo--bar", response.getContentAsString());
 	}
 
 	@Test
@@ -1970,7 +1970,7 @@ public class ServletAnnotationControllerTests {
 
 		@RequestMapping("/myPath.do")
 		public void myHandle(@RequestParam(value = "id", defaultValue = "foo") String id,
-				@RequestParam(value = "otherId", required = false) String id2,
+				@RequestParam(value = "otherId", defaultValue = "") String id2,
 				@RequestHeader(defaultValue = "bar") String header,
 				HttpServletResponse response) throws IOException {
 			response.getWriter().write(String.valueOf(id) + "-" + String.valueOf(id2) + "-" + String.valueOf(header));

org.springframework.web/src/main/java/org/springframework/web/bind/annotation/CookieValue.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2010 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.
@@ -63,6 +63,6 @@ public @interface CookieValue {
 	 * The default value to use as a fallback. Supplying a default value implicitly
 	 * sets {@link #required()} to false.
 	 */
-	String defaultValue() default "";
+	String defaultValue() default ValueConstants.DEFAULT_NONE;
 
 }

org.springframework.web/src/main/java/org/springframework/web/bind/annotation/RequestHeader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2010 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.
@@ -58,6 +58,6 @@ public @interface RequestHeader {
 	 * The default value to use as a fallback. Supplying a default value implicitely
 	 * sets {@link #required()} to false.
 	 */
-	String defaultValue() default "";
+	String defaultValue() default ValueConstants.DEFAULT_NONE;
 
 }

org.springframework.web/src/main/java/org/springframework/web/bind/annotation/RequestParam.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2010 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.
@@ -60,6 +60,6 @@ public @interface RequestParam {
 	 * The default value to use as a fallback. Supplying a default value implicitly
 	 * sets {@link #required()} to false.
 	 */
-	String defaultValue() default "";
+	String defaultValue() default ValueConstants.DEFAULT_NONE;
 
 }

org.springframework.web/src/main/java/org/springframework/web/bind/annotation/ValueConstants.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2002-2010 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.web.bind.annotation;
+
+/**
+ * Common value constants shared between bind annotations.
+ *
+ * @author Juergen Hoeller
+ * @since 3.0.1
+ */
+public interface ValueConstants {
+
+	/**
+	 * Constant defining a value for no default - as a replacement for
+	 * <code>null</code> which we cannot use in annotation attributes.
+	 * <p>This is an artificial arrangement of 16 unicode characters,
+	 * with its sole purpose being to never match user-declared values.
+	 * @see RequestParam#defaultValue()
+	 * @see RequestHeader#defaultValue()
+	 * @see CookieValue#defaultValue()
+	 */
+	String DEFAULT_NONE = "\n\t\t\n\t\t\n\uE000\uE001\uE002\n\t\t\t\t\n";
+
+}

org.springframework.web/src/main/java/org/springframework/web/bind/annotation/support/HandlerMethodInvoker.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2010 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.
@@ -50,7 +50,6 @@ import org.springframework.util.ClassUtils;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.util.ReflectionUtils;
-import org.springframework.util.StringUtils;
 import org.springframework.validation.BindException;
 import org.springframework.validation.BindingResult;
 import org.springframework.validation.Errors;
@@ -63,6 +62,7 @@ import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestHeader;
 import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.ValueConstants;
 import org.springframework.web.bind.support.DefaultSessionAttributeStore;
 import org.springframework.web.bind.support.SessionAttributeStore;
 import org.springframework.web.bind.support.SessionStatus;
@@ -200,14 +200,14 @@ public class HandlerMethodInvoker {
 					RequestParam requestParam = (RequestParam) paramAnn;
 					paramName = requestParam.value();
 					required = requestParam.required();
-					defaultValue = requestParam.defaultValue();
+					defaultValue = parseDefaultValueAttribute(requestParam.defaultValue());
 					found++;
 				}
 				else if (RequestHeader.class.isInstance(paramAnn)) {
 					RequestHeader requestHeader = (RequestHeader) paramAnn;
 					headerName = requestHeader.value();
 					required = requestHeader.required();
-					defaultValue = requestHeader.defaultValue();
+					defaultValue = parseDefaultValueAttribute(requestHeader.defaultValue());
 					found++;
 				}
 				else if (RequestBody.class.isInstance(paramAnn)) {
@@ -218,7 +218,7 @@ public class HandlerMethodInvoker {
 					CookieValue cookieValue = (CookieValue) paramAnn;
 					cookieName = cookieValue.value();
 					required = cookieValue.required();
-					defaultValue = cookieValue.defaultValue();
+					defaultValue = parseDefaultValueAttribute(cookieValue.defaultValue());
 					found++;
 				}
 				else if (PathVariable.class.isInstance(paramAnn)) {
@@ -430,7 +430,7 @@ public class HandlerMethodInvoker {
 			}
 		}
 		if (paramValue == null) {
-			if (StringUtils.hasText(defaultValue)) {
+			if (defaultValue != null) {
 				paramValue = resolveDefaultValue(defaultValue);
 			}
 			else if (required) {
@@ -483,7 +483,7 @@ public class HandlerMethodInvoker {
 			headerValue = (headerValues.length == 1 ? headerValues[0] : headerValues);
 		}
 		if (headerValue == null) {
-			if (StringUtils.hasText(defaultValue)) {
+			if (defaultValue != null) {
 				headerValue = resolveDefaultValue(defaultValue);
 			}
 			else if (required) {
@@ -566,7 +566,7 @@ public class HandlerMethodInvoker {
 		}
 		Object cookieValue = resolveCookieValue(cookieName, paramType, webRequest);
 		if (cookieValue == null) {
-			if (StringUtils.hasText(defaultValue)) {
+			if (defaultValue != null) {
 				cookieValue = resolveDefaultValue(defaultValue);
 			}
 			else if (required) {
@@ -762,6 +762,10 @@ public class HandlerMethodInvoker {
 		throw new UnsupportedOperationException("@RequestBody not supported");
 	}
 
+	protected String parseDefaultValueAttribute(String value) {
+		return (ValueConstants.DEFAULT_NONE.equals(value) ? null : value);
+	}
+
 	protected Object resolveDefaultValue(String value) {
 		return value;
 	}