HttpEntity.EMPTY should be immutable

Fix GH-34806

Signed-off-by: Yanming Zhou <[email protected]>

Author: quaff

spring-web/src/main/java/org/springframework/http/HttpHeaders.java

@@ -92,6 +92,7 @@
  * @author Josh Long
  * @author Sam Brannen
  * @author Simon Baslé
+ * @author Yanming Zhou
  * @since 3.0
  */
 public class HttpHeaders implements Serializable {
@@ -473,10 +474,7 @@ public HttpHeaders(HttpHeaders httpHeaders) {
 			this.headers = CollectionUtils.toMultiValueMap(new LinkedCaseInsensitiveMap<>(8, Locale.ENGLISH));
 		}
 		else {
-			while (httpHeaders.headers instanceof HttpHeaders wrapped) {
-				httpHeaders = wrapped;
-			}
-			this.headers = httpHeaders.headers;
+			this.headers = new LinkedMultiValueMap<>(httpHeaders.headers);
 		}
 	}
 

spring-web/src/test/java/org/springframework/http/HttpEntityTests.java

@@ -24,6 +24,7 @@
 
 /**
  * @author Arjen Poutsma
+ * @author Yanming Zhou
  */
 class HttpEntityTests {
 
@@ -120,4 +121,11 @@ void requestEntity() {
 		assertThat(requestEntity2).isEqualTo(requestEntity);
 	}
 
+	@Test
+	void emptyHttpEntityShouldBeImmutable() {
+		HttpHeaders newHeaders = new HttpHeaders(HttpEntity.EMPTY.getHeaders());
+		newHeaders.add("Authorization", "Bearer some-token");
+		assertThat(HttpEntity.EMPTY.getHeaders().headerNames()).isEmpty();
+	}
+
 }