Polishing contribution

Closes gh-34230

Author: rstoyanchev

framework-docs/modules/ROOT/pages/integration/rest-clients.adoc

@@ -938,10 +938,10 @@ method parameters:
 | Dynamically set the HTTP method for the request, overriding the annotation's `method` attribute
 
 | `@RequestHeader`
-| Add a request header or multiple headers. The argument may be a `Map<String, ?>` or
-  `MultiValueMap<String, ?>` with multiple headers, a `Collection<?>` of values, or an
-  individual value. Type conversion is supported for non-String values. This does not override
-  the annotation's `headers` attribute.
+| Add a request header or multiple headers. The argument may be a single value,
+  a `Collection<?>` of values, `Map<String, ?>`,`MultiValueMap<String, ?>`.
+  Type conversion is supported for non-String values. Header values are added and
+  do not override already added header values.
 
 | `@PathVariable`
 | Add a variable for expand a placeholder in the request URL. The argument may be a

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

@@ -53,8 +53,8 @@ void header() {
 
 	@Test
 	void doesNotOverrideAnnotationHeaders() {
-		this.service.executeWithAnnotationHeaders("test");
-		assertRequestHeaders("id", "default", "test");
+		this.service.executeWithAnnotationHeaders("2");
+		assertRequestHeaders("myHeader", "1", "2");
 	}
 
 	private void assertRequestHeaders(String key, String... values) {
@@ -73,8 +73,8 @@ private interface Service {
 		@GetExchange
 		void execute(@RequestHeader String id);
 
-		@HttpExchange(method = "GET", headers = "id=default")
-		void executeWithAnnotationHeaders(@RequestHeader String id);
+		@HttpExchange(method = "GET", headers = "myHeader=1")
+		void executeWithAnnotationHeaders(@RequestHeader String myHeader);
 
 	}