DATACMNS-753 - Fixed default handling of empty sort parameter.

We now correctly inspect the sort parameter values and also fall back to the default if a single, empty parameter value is given.

Related ticket: DATACMNS-408.
Related pull request: #138.

Author: odrotbohm

src/main/java/org/springframework/data/web/SortHandlerMethodArgumentResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2014 the original author or authors.
+ * Copyright 2013-2015 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.
@@ -108,11 +108,17 @@ public Sort resolveArgument(MethodParameter parameter, ModelAndViewContainer mav
 
 		String[] directionParameter = webRequest.getParameterValues(getSortParameter(parameter));
 
-		if (directionParameter != null && directionParameter.length != 0) {
-			return parseParameterIntoSort(directionParameter, propertyDelimiter);
-		} else {
+		// No parameter
+		if (directionParameter == null) {
 			return getDefaultFromAnnotationOrFallback(parameter);
 		}
+
+		// Single empty parameter, e.g "sort="
+		if (directionParameter.length == 1 && !StringUtils.hasText(directionParameter[0])) {
+			return getDefaultFromAnnotationOrFallback(parameter);
+		}
+
+		return parseParameterIntoSort(directionParameter, propertyDelimiter);
 	}
 
 	/**
@@ -130,9 +136,9 @@ private Sort getDefaultFromAnnotationOrFallback(MethodParameter parameter) {
 		SortDefault annotatedDefault = parameter.getParameterAnnotation(SortDefault.class);
 
 		if (annotatedDefault != null && annotatedDefaults != null) {
-			throw new IllegalArgumentException(String.format(
-					"Cannot use both @%s and @%s on parameter %s! Move %s into %s to define sorting order!", SORT_DEFAULTS_NAME,
-					SORT_DEFAULT_NAME, parameter.toString(), SORT_DEFAULT_NAME, SORT_DEFAULTS_NAME));
+			throw new IllegalArgumentException(
+					String.format("Cannot use both @%s and @%s on parameter %s! Move %s into %s to define sorting order!",
+							SORT_DEFAULTS_NAME, SORT_DEFAULT_NAME, parameter.toString(), SORT_DEFAULT_NAME, SORT_DEFAULTS_NAME));
 		}
 
 		if (annotatedDefault != null) {

src/test/java/org/springframework/data/web/SortHandlerMethodArgumentResolverUnitTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 the original author or authors.
+ * Copyright 2013-2015 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.
@@ -149,21 +149,6 @@ public void parsesEmptySortToNull() throws Exception {
 		assertThat(resolveSort(request, PARAMETER), is(nullValue()));
 	}
 
-	/**
-	 *
-	 * @see DATACMNS-753
-	 * see also DATACMNS-408
-	 */
-	@Test
-	public void doesNotReturnNullWhenAnnotatedWithSortDefault() throws Exception {
-
-		MockHttpServletRequest request = new MockHttpServletRequest();
-		request.addParameter("sort", ""); //valid input
-
-		assertNotNull(resolveSort(request, getParameterOfMethod("simpleDefault")));
-		assertNotNull(resolveSort(request, getParameterOfMethod("containeredDefault")));
-	}
-
 	/**
 	 * @see DATACMNS-408
 	 */
@@ -213,6 +198,19 @@ public void parsesCommaParameterForSort() throws Exception {
 		assertThat(resolveSort(request, PARAMETER), is(nullValue()));
 	}
 
+	/**
+	 * @see DATACMNS-753, DATACMNS-408
+	 */
+	@Test
+	public void doesNotReturnNullWhenAnnotatedWithSortDefault() throws Exception {
+
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.addParameter("sort", "");
+
+		assertThat(resolveSort(request, getParameterOfMethod("simpleDefault")), is(new Sort("firstname", "lastname")));
+		assertThat(resolveSort(request, getParameterOfMethod("containeredDefault")), is(new Sort("foo", "bar")));
+	}
+
 	private static Sort resolveSort(HttpServletRequest request, MethodParameter parameter) throws Exception {
 
 		SortHandlerMethodArgumentResolver resolver = new SortHandlerMethodArgumentResolver();