Restore 2 digit days format in HttpHeaders

As recommended by RFC 7231, this commit restore using 2 digit days
when formatting dates while still using
DateTimeFormatter.RFC_1123_DATE_TIME for parsing.

Closes gh-22478

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

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -169,7 +169,7 @@ public class MockHttpServletResponseTests {
 		response.addCookie(cookie);
 
 		assertEquals("foo=bar; Path=/path; Domain=example.com; " +
-				"Max-Age=0; Expires=Thu, 1 Jan 1970 00:00:00 GMT; " +
+				"Max-Age=0; Expires=Thu, 01 Jan 1970 00:00:00 GMT; " +
 				"Secure; HttpOnly", response.getHeader(HttpHeaders.SET_COOKIE));
 	}
 
@@ -349,7 +349,7 @@ public class MockHttpServletResponseTests {
 		response.addCookie(mockCookie);
 
 		assertEquals("SESSION=123; Path=/; Domain=example.com; Max-Age=0; " +
-				"Expires=Thu, 1 Jan 1970 00:00:00 GMT; Secure; HttpOnly; SameSite=Lax",
+				"Expires=Thu, 01 Jan 1970 00:00:00 GMT; Secure; HttpOnly; SameSite=Lax",
 				response.getHeader(HttpHeaders.SET_COOKIE));
 	}
 

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

@@ -394,12 +394,18 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	private static final ZoneId GMT = ZoneId.of("GMT");
 
 	/**
-	 * Date formats with time zone as specified in the HTTP RFC.
+	 * Date formats with time zone as specified in the HTTP RFC to use for formatting.
 	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.1.1">Section 7.1.1.1 of RFC 7231</a>
 	 */
-	private static final DateTimeFormatter[] DATE_FORMATTERS = new DateTimeFormatter[] {
+	private static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US).withZone(GMT);
+
+	/**
+	 * Date formats with time zone as specified in the HTTP RFC to use for parsing.
+	 * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.1.1">Section 7.1.1.1 of RFC 7231</a>
+	 */
+	private static final DateTimeFormatter[] DATE_PARSERS = new DateTimeFormatter[] {
 			DateTimeFormatter.RFC_1123_DATE_TIME,
-			DateTimeFormatter.ofPattern("EEEE, dd-MMM-yy HH:mm:ss zz", Locale.US),
+			DateTimeFormatter.ofPattern("EEEE, dd-MMM-yy HH:mm:ss zzz", Locale.US),
 			DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss yyyy", Locale.US).withZone(GMT)
 	};
 
@@ -1322,7 +1328,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	 * @since 5.0
 	 */
 	public void setZonedDateTime(String headerName, ZonedDateTime date) {
-		set(headerName, DATE_FORMATTERS[0].format(date));
+		set(headerName, DATE_FORMATTER.format(date));
 	}
 
 	/**
@@ -1417,7 +1423,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 				headerValue = headerValue.substring(0, parametersIndex);
 			}
 
-			for (DateTimeFormatter dateFormatter : DATE_FORMATTERS) {
+			for (DateTimeFormatter dateFormatter : DATE_PARSERS) {
 				try {
 					return ZonedDateTime.parse(headerValue, dateFormatter);
 				}
@@ -1733,7 +1739,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	static String formatDate(long date) {
 		Instant instant = Instant.ofEpochMilli(date);
 		ZonedDateTime time = ZonedDateTime.ofInstant(instant, GMT);
-		return DATE_FORMATTERS[0].format(time);
+		return DATE_FORMATTER.format(time);
 	}
 
 }

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

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -21,7 +21,6 @@ import java.net.URI;
 import java.net.URISyntaxException;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
-import java.time.DateTimeException;
 import java.time.ZoneId;
 import java.time.ZonedDateTime;
 import java.util.ArrayList;
@@ -38,7 +37,6 @@ import java.util.TimeZone;
 import org.hamcrest.Matchers;
 import org.junit.Test;
 
-import static java.time.format.DateTimeFormatter.*;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
@@ -299,11 +297,6 @@ public class HttpHeadersTests {
 		assertEquals("Invalid Expires header", "Thu, 18 Dec 2008 10:20:00 GMT", headers.getFirst("expires"));
 	}
 
-	@Test(expected = DateTimeException.class)  // SPR-16560
-	public void expiresLargeDate() {
-		headers.setExpires(Long.MAX_VALUE);
-	}
-
 	@Test  // SPR-10648 (example is from INT-3063)
 	public void expiresInvalidDate() {
 		headers.set("Expires", "-1");
@@ -503,37 +496,37 @@ public class HttpHeadersTests {
 
 	@Test
 	public void firstDate() {
-		headers.setDate(HttpHeaders.DATE, 1229595600000L);
-		assertThat(headers.getFirstDate(HttpHeaders.DATE), is(1229595600000L));
+		headers.setDate(HttpHeaders.DATE, 1496370120000L);
+		assertThat(headers.getFirstDate(HttpHeaders.DATE), is(1496370120000L));
 
 		headers.clear();
 
-		headers.add(HttpHeaders.DATE, "Thu, 18 Dec 2008 10:20:00 GMT");
+		headers.add(HttpHeaders.DATE, "Fri, 02 Jun 2017 02:22:00 GMT");
 		headers.add(HttpHeaders.DATE, "Sat, 18 Dec 2010 10:20:00 GMT");
-		assertThat(headers.getFirstDate(HttpHeaders.DATE), is(1229595600000L));
+		assertThat(headers.getFirstDate(HttpHeaders.DATE), is(1496370120000L));
 	}
 
 	@Test
 	public void firstZonedDateTime() {
-		ZonedDateTime date = ZonedDateTime.of(2017, 6, 22, 22, 22, 0, 0, ZoneId.of("GMT"));
+		ZonedDateTime date = ZonedDateTime.of(2017, 6, 2, 2, 22, 0, 0, ZoneId.of("GMT"));
 		headers.setZonedDateTime(HttpHeaders.DATE, date);
-		assertThat(headers.getFirst(HttpHeaders.DATE), is("Thu, 22 Jun 2017 22:22:00 GMT"));
+		assertThat(headers.getFirst(HttpHeaders.DATE), is("Fri, 02 Jun 2017 02:22:00 GMT"));
 		assertTrue(headers.getFirstZonedDateTime(HttpHeaders.DATE).isEqual(date));
 
 		headers.clear();
 		ZonedDateTime otherDate = ZonedDateTime.of(2010, 12, 18, 10, 20, 0, 0, ZoneId.of("GMT"));
-		headers.add(HttpHeaders.DATE, RFC_1123_DATE_TIME.format(date));
-		headers.add(HttpHeaders.DATE, RFC_1123_DATE_TIME.format(otherDate));
+		headers.add(HttpHeaders.DATE, "Fri, 02 Jun 2017 02:22:00 GMT");
+		headers.add(HttpHeaders.DATE, "Sat, 18 Dec 2010 10:20:00 GMT");
 		assertTrue(headers.getFirstZonedDateTime(HttpHeaders.DATE).isEqual(date));
 
 		// obsolete RFC 850 format
 		headers.clear();
-		headers.set(HttpHeaders.DATE, "Thursday, 22-Jun-17 22:22:00 GMT");
+		headers.set(HttpHeaders.DATE, "Friday, 02-Jun-17 02:22:00 GMT");
 		assertTrue(headers.getFirstZonedDateTime(HttpHeaders.DATE).isEqual(date));
 
 		// ANSI C's asctime() format
 		headers.clear();
-		headers.set(HttpHeaders.DATE, "Thu Jun 22 22:22:00 2017");
+		headers.set(HttpHeaders.DATE, "Fri Jun 02 02:22:00 2017");
 		assertTrue(headers.getFirstZonedDateTime(HttpHeaders.DATE).isEqual(date));
 	}
 

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

 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -115,7 +115,7 @@ public class RequestEntityTests {
 
 		assertEquals("text/plain", responseHeaders.getFirst("Accept"));
 		assertEquals("utf-8", responseHeaders.getFirst("Accept-Charset"));
-		assertEquals("Thu, 1 Jan 1970 00:00:12 GMT", responseHeaders.getFirst("If-Modified-Since"));
+		assertEquals("Thu, 01 Jan 1970 00:00:12 GMT", responseHeaders.getFirst("If-Modified-Since"));
 		assertEquals(ifNoneMatch, responseHeaders.getFirst("If-None-Match"));
 		assertEquals(String.valueOf(contentLength), responseHeaders.getFirst("Content-Length"));
 		assertEquals(contentType.toString(), responseHeaders.getFirst("Content-Type"));

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

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -59,10 +59,10 @@ public class ResponseCookieTests {
 
 	@Test
 	public void maxAge0() {
-		assertEquals("id=1fWa; Max-Age=0; Expires=Thu, 1 Jan 1970 00:00:00 GMT",
+		assertEquals("id=1fWa; Max-Age=0; Expires=Thu, 01 Jan 1970 00:00:00 GMT",
 				ResponseCookie.from("id", "1fWa").maxAge(Duration.ofSeconds(0)).build().toString());
 
-		assertEquals("id=1fWa; Max-Age=0; Expires=Thu, 1 Jan 1970 00:00:00 GMT",
+		assertEquals("id=1fWa; Max-Age=0; Expires=Thu, 01 Jan 1970 00:00:00 GMT",
 				ResponseCookie.from("id", "1fWa").maxAge(0).build().toString());
 	}
 

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

 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -180,7 +180,7 @@ public class ResponseEntityTests {
 		HttpHeaders responseHeaders = responseEntity.getHeaders();
 
 		assertEquals("GET", responseHeaders.getFirst("Allow"));
-		assertEquals("Thu, 1 Jan 1970 00:00:12 GMT",
+		assertEquals("Thu, 01 Jan 1970 00:00:12 GMT",
 				responseHeaders.getFirst("Last-Modified"));
 		assertEquals(location.toASCIIString(),
 				responseHeaders.getFirst("Location"));