Empty string check after conversion in AbstractNamedValueArgumentResolver

Closes gh-33794

Author: rstoyanchev

spring-web/src/main/java/org/springframework/web/service/invoker/AbstractNamedValueArgumentResolver.java

@@ -32,6 +32,7 @@
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
 import org.springframework.web.bind.annotation.ValueConstants;
 
 /**
@@ -191,11 +192,15 @@ private void addSingleValue(
 		}
 
 		if (this.conversionService != null && !(value instanceof String)) {
+			Object beforeValue = value;
 			parameter = parameter.nestedIfOptional();
 			Class<?> type = parameter.getNestedParameterType();
 			value = (type != Object.class && !type.isArray() ?
 					this.conversionService.convert(value, new TypeDescriptor(parameter), STRING_TARGET_TYPE) :
 					this.conversionService.convert(value, String.class));
+			if (!StringUtils.hasText((String) value) && !required && beforeValue == null) {
+				value = null;
+			}
 		}
 
 		if (value == null) {

spring-web/src/test/java/org/springframework/web/service/invoker/NamedValueArgumentResolverTests.java

@@ -74,6 +74,12 @@ void dateTestValue() {
 		assertTestValue("value", "2022-09-16");
 	}
 
+	@Test // gh-33794
+	void dateNullValue() {
+		this.service.executeDate(null);
+		assertTestValue("value");
+	}
+
 	@Test
 	void objectTestValue() {
 		this.service.execute(Boolean.TRUE);
@@ -182,7 +188,7 @@ private interface Service {
 		void executeString(@TestValue String value);
 
 		@GetExchange
-		void executeDate(@TestValue @DateTimeFormat(pattern = "yyyy-MM-dd") LocalDate value);
+		void executeDate(@Nullable @TestValue(required = false) @DateTimeFormat(pattern = "yyyy-MM-dd") LocalDate value);
 
 		@GetExchange
 		void execute(@TestValue Object value);