Merge branch '6.2.x'

spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java

@@ -681,7 +681,12 @@ public class MockHttpServletResponse implements HttpServletResponse {
 
 	@Override
 	public void setHeader(String name, @Nullable String value) {
-		setHeaderValue(name, value);
+		if (value == null) {
+			this.headers.remove(name);
+		}
+		else {
+			setHeaderValue(name, value);
+		}
 	}
 
 	@Override

spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java

@@ -88,6 +88,18 @@ class MockHttpServletResponseTests {
 		assertThat(response.containsHeader(headerName)).isFalse();
 	}
 
+	@ParameterizedTest
+	@ValueSource(strings = {
+			CONTENT_TYPE,
+			CONTENT_LANGUAGE,
+			"X-Test-Header"
+	})
+	void removeHeaderIfNullValue(String headerName) {
+		response.addHeader(headerName, "test");
+		response.setHeader(headerName, null);
+		assertThat(response.containsHeader(headerName)).isFalse();
+	}
+
 	@Test  // gh-26493
 	void setLocaleWithNullValue() {
 		assertThat(response.getLocale()).isEqualTo(Locale.getDefault());

spring-web/src/main/java/org/springframework/web/util/ContentCachingResponseWrapper.java

@@ -161,7 +161,13 @@ public class ContentCachingResponseWrapper extends HttpServletResponseWrapper {
 	@Override
 	public void setHeader(String name, String value) {
 		if (HttpHeaders.CONTENT_LENGTH.equalsIgnoreCase(name)) {
-			this.contentLength = toContentLengthInt(Long.parseLong(value));
+			if (value != null) {
+				this.contentLength = toContentLengthInt(Long.parseLong(value));
+			}
+			else {
+				this.contentLength = null;
+				super.setHeader(name, null);
+			}
 		}
 		else {
 			super.setHeader(name, value);

spring-web/src/test/java/org/springframework/web/filter/ContentCachingResponseWrapperTests.java

@@ -270,6 +270,17 @@ class ContentCachingResponseWrapperTests {
 				.withMessageContaining(overflow);
 	}
 
+	@Test
+	void setContentLengthNull() {
+		MockHttpServletResponse response = new MockHttpServletResponse();
+		ContentCachingResponseWrapper responseWrapper = new ContentCachingResponseWrapper(response);
+		responseWrapper.setContentLength(1024);
+		responseWrapper.setHeader(CONTENT_LENGTH, null);
+
+		assertThat(response.getHeaderNames()).doesNotContain(CONTENT_LENGTH);
+		assertThat(responseWrapper.getHeader(CONTENT_LENGTH)).isNull();
+	}
+
 
 	private void assertHeader(HttpServletResponse response, String header, int value) {
 		assertHeader(response, header, Integer.toString(value));

spring-web/src/testFixtures/java/org/springframework/web/testfixture/servlet/MockHttpServletResponse.java

@@ -681,7 +681,12 @@ public class MockHttpServletResponse implements HttpServletResponse {
 
 	@Override
 	public void setHeader(String name, @Nullable String value) {
-		setHeaderValue(name, value);
+		if (value == null) {
+			this.headers.remove(name);
+		}
+		else {
+			setHeaderValue(name, value);
+		}
 	}
 
 	@Override