Consistent handling of parts in HttpRequestValues

Closes gh-30520

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

@@ -389,14 +389,15 @@ public final class HttpRequestValues {
 			Map<String, String> uriVars = (this.uriVars != null ? new HashMap<>(this.uriVars) : Collections.emptyMap());
 
 			Object bodyValue = this.bodyValue;
+			if (this.multipartBuilder != null) {
+				Assert.isTrue(bodyValue == null && this.body == null, "Expected body or request parts, not both");
+				bodyValue = this.multipartBuilder.build();
+			}
 
 			if (!CollectionUtils.isEmpty(this.requestParams)) {
-
-				boolean isFormData = (this.headers != null &&
-						MediaType.APPLICATION_FORM_URLENCODED.equals(this.headers.getContentType()));
-
-				if (isFormData) {
-					Assert.isTrue(bodyValue == null && this.body == null, "Expected body or request params, not both");
+				if (hasContentType(MediaType.APPLICATION_FORM_URLENCODED)) {
+					Assert.isTrue(this.multipartBuilder == null, "Cannot add parts to form data request");
+					Assert.isTrue(bodyValue == null && this.body == null, "Cannot set body of form data request");
 					bodyValue = new LinkedMultiValueMap<>(this.requestParams);
 				}
 				else if (uri != null) {
@@ -412,10 +413,6 @@ public final class HttpRequestValues {
 					uriTemplate = appendQueryParams(uriTemplate, uriVars, this.requestParams);
 				}
 			}
-			else if (this.multipartBuilder != null) {
-				Assert.isTrue(bodyValue == null && this.body == null, "Expected body or request parts, not both");
-				bodyValue = this.multipartBuilder.build();
-			}
 
 			HttpHeaders headers = HttpHeaders.EMPTY;
 			if (this.headers != null) {
@@ -434,6 +431,10 @@ public final class HttpRequestValues {
 					bodyValue, this.body, this.bodyElementType);
 		}
 
+		private boolean hasContentType(MediaType mediaType) {
+			return (this.headers != null && mediaType.equals(this.headers.getContentType()));
+		}
+
 		private String appendQueryParams(
 				String uriTemplate, Map<String, String> uriVars, MultiValueMap<String, String> requestParams) {
 

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

@@ -131,4 +131,24 @@ class HttpRequestValuesTests {
 		assertThat(map.getFirst("entity")).isEqualTo(entity);
 	}
 
+	@Test
+	void requestPartAndRequestParam() {
+
+		HttpRequestValues requestValues = HttpRequestValues.builder()
+				.setUriTemplate("/path")
+				.addRequestPart("form field", "form value")
+				.addRequestParameter("query param", "query value")
+				.build();
+
+		String uriTemplate = requestValues.getUriTemplate();
+		assertThat(uriTemplate).isNotNull();
+
+		assertThat(uriTemplate).isEqualTo("/path?{queryParam0}={queryParam0[0]}");
+
+		@SuppressWarnings("unchecked")
+		MultiValueMap<String, HttpEntity<?>> map = (MultiValueMap<String, HttpEntity<?>>) requestValues.getBodyValue();
+		assertThat(map).hasSize(1);
+		assertThat(map.getFirst("form field").getBody()).isEqualTo("form value");
+	}
+
 }