Merge pull request #33156 from

* pr/33156:
  Polish "Implement DefaultErrorResponseBuilder#headers(Consumer)"
  Implement DefaultErrorResponseBuilder#headers(Consumer)

Closes gh-33156

spring-web/src/main/java/org/springframework/web/DefaultErrorResponseBuilder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -66,18 +66,25 @@ final class DefaultErrorResponseBuilder implements ErrorResponse.Builder {
 
 	@Override
 	public ErrorResponse.Builder header(String headerName, String... headerValues) {
-		this.headers = (this.headers != null ? this.headers : new HttpHeaders());
 		for (String headerValue : headerValues) {
-			this.headers.add(headerName, headerValue);
+			getHeaders().add(headerName, headerValue);
 		}
 		return this;
 	}
 
 	@Override
 	public ErrorResponse.Builder headers(Consumer<HttpHeaders> headersConsumer) {
+		headersConsumer.accept(getHeaders());
 		return this;
 	}
 
+	private HttpHeaders getHeaders() {
+		if (this.headers == null) {
+			this.headers = new HttpHeaders();
+		}
+		return this.headers;
+	}
+
 	@Override
 	public ErrorResponse.Builder type(URI type) {
 		this.problemDetail.setType(type);

spring-web/src/test/java/org/springframework/web/ErrorResponseTests.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.http.HttpStatus;
+
+import static java.util.Map.entry;
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ErrorResponse}.
+ *
+ * @author Stephane Nicoll
+ */
+class ErrorResponseTests {
+
+	@Test
+	void createWithHttpHeader() {
+		ErrorResponse response = ErrorResponse.builder(new IllegalStateException(), HttpStatus.BAD_REQUEST, "test")
+				.header("header", "value").build();
+		assertThat(response.getHeaders()).containsOnly(entry("header", List.of("value")));
+	}
+
+	@Test
+	void createWithHttpHeadersConsumer() {
+		ErrorResponse response = ErrorResponse.builder(new IllegalStateException(), HttpStatus.BAD_REQUEST, "test")
+				.header("header", "value")
+				.headers(headers -> {
+					headers.add("header", "value2");
+					headers.add("another", "value3");
+				}).build();
+		assertThat(response.getHeaders()).containsOnly(entry("header", List.of("value", "value2")),
+				entry("another", List.of("value3")));
+	}
+
+}