DATACMNS-1827 - Pageable and Sort arguments with empty qualifier value shouldn't be prefixed with delimiter.

Original pull request: #473.

Author: vpavic

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

@@ -230,7 +230,7 @@ protected String getParameterNameToUse(String source, @Nullable MethodParameter
 
 		Qualifier qualifier = parameter == null ? null : parameter.getParameterAnnotation(Qualifier.class);
 
-		if (qualifier != null) {
+		if (qualifier != null && StringUtils.hasLength(qualifier.value())) {
 			builder.append(qualifier.value());
 			builder.append(qualifierDelimiter);
 		}

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

@@ -186,8 +186,9 @@ protected String getSortParameter(@Nullable MethodParameter parameter) {
 
 		Qualifier qualifier = parameter != null ? parameter.getParameterAnnotation(Qualifier.class) : null;
 
-		if (qualifier != null) {
-			builder.append(qualifier.value()).append(qualifierDelimiter);
+		if (qualifier != null && StringUtils.hasLength(qualifier.value())) {
+			builder.append(qualifier.value());
+			builder.append(qualifierDelimiter);
 		}
 
 		return builder.append(sortParameter).toString();

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

@@ -35,6 +35,7 @@
  *
  * @author Oliver Gierke
  * @author Nick Williams
+ * @author Vedran Pavic
  */
 class PageableHandlerMethodArgumentResolverUnitTests extends PageableDefaultUnitTests {
 
@@ -244,6 +245,18 @@ void detectsFallbackPageableIfNullOneIsConfigured() {
 		assertThat(resolver.isFallbackPageable(PageRequest.of(0, 10))).isFalse();
 	}
 
+	@Test // DATACMNS-1827
+	void emptyQualifierIsUsedInParameterLookup() throws Exception {
+
+		MethodParameter parameter = new MethodParameter(Sample.class.getMethod("emptyQualifier", Pageable.class), 0);
+
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.addParameter("page", "2");
+		request.addParameter("size", "10");
+
+		assertSupportedAndResult(parameter, PageRequest.of(2, 10), request);
+	}
+
 	@Override
 	protected PageableHandlerMethodArgumentResolver getResolver() {
 		PageableHandlerMethodArgumentResolver resolver = new PageableHandlerMethodArgumentResolver();
@@ -283,5 +296,7 @@ void simpleDefaultWithContaineredExternalSort(@PageableDefault(size = PAGE_SIZE,
 		void validQualifier(@Qualifier("foo") Pageable pageable);
 
 		void noQualifiers(Pageable first, Pageable second);
+
+		void emptyQualifier(@Qualifier Pageable pageable);
 	}
 }

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

@@ -45,6 +45,7 @@
  * @author Thomas Darimont
  * @author Nick Williams
  * @author Mark Paluch
+ * @author Vedran Pavic
  */
 class SortHandlerMethodArgumentResolverUnitTests extends SortDefaultUnitTests {
 
@@ -241,6 +242,15 @@ void resolvesDotOnlyInputToDefault() {
 		});
 	}
 
+	@Test // DATACMNS-1827
+	void emptyQualifierIsUsedInParameterLookup() {
+
+		MethodParameter parameter = getParameterOfMethod("emptyQualifier");
+		Sort reference = Sort.by("bar", "foo");
+
+		assertSupportedAndResolvedTo(getRequestWithSort(reference, ""), parameter, reference);
+	}
+
 	private static Sort resolveSort(HttpServletRequest request, MethodParameter parameter) throws Exception {
 
 		SortHandlerMethodArgumentResolver resolver = new SortHandlerMethodArgumentResolver();
@@ -306,5 +316,7 @@ void simpleDefaultWithDirectionCaseInsensitive(
 		void containeredDefault(@SortDefaults(@SortDefault({ "foo", "bar" })) Sort sort);
 
 		void invalid(@SortDefaults(@SortDefault({ "foo", "bar" })) @SortDefault({ "bar", "foo" }) Sort sort);
+
+		void emptyQualifier(@Qualifier Sort sort);
 	}
 }