Leverage ZonedDateTime in HttpHeaders

This commit introduces 2 new public methods in HttpHeaders in order
to leverage Java 8 ZonedDateTime in addition to the existing long
(with GMT time zone implied) variants:
 - ZonedDateTime getFirstZonedDateTime(String headerName)
 - void setZonedDateTime(String headerName, ZonedDateTime date)

This commit also leverages Java 8 thread-safe DateTimeFormatter for
HttpHeader implementation instead of SimpleDateFormat. As a consequence
of the usage of DateTimeFormatter.RFC_1123_DATE_TIME, HTTP date header
serialization could change slightly for single digit days from for
example "Thu, 01 Jan 1970 00:00:00 GMT" to
"Thu, 1 Jan 1970 00:00:00 GMT".

Issue: SPR-15661

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

@@ -169,7 +169,7 @@ public void cookies() {
 		response.addCookie(cookie);
 
 		assertEquals("foo=bar; Path=/path; Domain=example.com; " +
-				"Max-Age=0; Expires=Thu, 01 Jan 1970 00:00:00 GMT; " +
+				"Max-Age=0; Expires=Thu, 1 Jan 1970 00:00:00 GMT; " +
 				"Secure; HttpOnly", response.getHeader(HttpHeaders.SET_COOKIE));
 	}
 

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

@@ -22,12 +22,14 @@
 import java.nio.charset.Charset;
 import java.text.DecimalFormat;
 import java.text.DecimalFormatSymbols;
-import java.text.ParseException;
-import java.text.SimpleDateFormat;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.Date;
 import java.util.EnumSet;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
@@ -36,7 +38,6 @@
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
-import java.util.TimeZone;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
@@ -47,6 +48,7 @@
 import org.springframework.util.MultiValueMap;
 import org.springframework.util.StringUtils;
 
+
 /**
  * Represents HTTP request and response headers, mapping string header names to a list of string values.
  *
@@ -372,16 +374,6 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	 */
 	public static final String WWW_AUTHENTICATE = "WWW-Authenticate";
 
-	/**
-	 * Date formats as specified in the HTTP RFC
-	 * @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 String[] DATE_FORMATS = new String[] {
-			"EEE, dd MMM yyyy HH:mm:ss zzz",
-			"EEE, dd-MMM-yy HH:mm:ss zzz",
-			"EEE MMM dd HH:mm:ss yyyy"
-	};
-
 	/**
 	 * Pattern matching ETag multiple field values in headers such as "If-Match", "If-None-Match"
 	 * @see <a href="https://tools.ietf.org/html/rfc7232#section-2.3">Section 2.3 of RFC 7232</a>
@@ -390,7 +382,17 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 
 	private static final DecimalFormatSymbols DECIMAL_FORMAT_SYMBOLS = new DecimalFormatSymbols(Locale.ENGLISH);
 
-	private static TimeZone GMT = TimeZone.getTimeZone("GMT");
+	private static final ZoneId GMT = ZoneId.of("GMT");
+
+	/**
+	 * Date formats with time zone as specified in the HTTP RFC
+	 * @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[] {
+			DateTimeFormatter.RFC_1123_DATE_TIME,
+			DateTimeFormatter.ofPattern("EEEE, dd-MMM-yy HH:mm:ss zz", Locale.US),
+			DateTimeFormatter.ofPattern("EEE MMM dd HH:mm:ss yyyy",Locale.US).withZone(GMT)
+	};
 
 
 	private final Map<String, List<String>> headers;
@@ -924,6 +926,7 @@ public void setExpires(long expires) {
 	 * as specified by the {@code Expires} header.
 	 * <p>The date is returned as the number of milliseconds since
 	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
+	 * @see #getFirstZonedDateTime(String)
 	 */
 	public long getExpires() {
 		return getFirstDate(EXPIRES, false);
@@ -1010,6 +1013,7 @@ public void setIfModifiedSince(long ifModifiedSince) {
 	 * Return the value of the {@code If-Modified-Since} header.
 	 * <p>The date is returned as the number of milliseconds since
 	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
+	 * @see #getFirstZonedDateTime(String)
 	 */
 	public long getIfModifiedSince() {
 		return getFirstDate(IF_MODIFIED_SINCE, false);
@@ -1051,6 +1055,7 @@ public void setIfUnmodifiedSince(long ifUnmodifiedSince) {
 	 * <p>The date is returned as the number of milliseconds since
 	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
 	 * @since 4.3
+	 * @see #getFirstZonedDateTime(String)
 	 */
 	public long getIfUnmodifiedSince() {
 		return getFirstDate(IF_UNMODIFIED_SINCE, false);
@@ -1071,6 +1076,7 @@ public void setLastModified(long lastModified) {
 	 * {@code Last-Modified} header.
 	 * <p>The date is returned as the number of milliseconds since
 	 * January 1, 1970 GMT. Returns -1 when the date is unknown.
+	 * @see #getFirstZonedDateTime(String)
 	 */
 	public long getLastModified() {
 		return getFirstDate(LAST_MODIFIED, false);
@@ -1178,14 +1184,25 @@ public List<String> getVary() {
 
 	/**
 	 * Set the given date under the given header name after formatting it as a string
-	 * using the pattern {@code "EEE, dd MMM yyyy HH:mm:ss zzz"}. The equivalent of
+	 * using the RFC-1123 date-time formatter. The equivalent of
 	 * {@link #set(String, String)} but for date headers.
 	 * @since 3.2.4
+	 * @see #setZonedDateTime(String, ZonedDateTime)
 	 */
 	public void setDate(String headerName, long date) {
-		SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMATS[0], Locale.US);
-		dateFormat.setTimeZone(GMT);
-		set(headerName, dateFormat.format(new Date(date)));
+		Instant instant = Instant.ofEpochMilli(date);
+		ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(instant, GMT);
+		set(headerName, DATE_FORMATTERS[0].format(zonedDateTime));
+	}
+
+	/**
+	 * Set the given date under the given header name after formatting it as a string
+	 * using the RFC-1123 date-time formatter. The equivalent of
+	 * {@link #set(String, String)} but for date headers.
+	 * @since 5.0
+	 */
+	public void setZonedDateTime(String headerName, ZonedDateTime date) {
+		set(headerName, DATE_FORMATTERS[0].format(date));
 	}
 
 	/**
@@ -1195,6 +1212,7 @@ public void setDate(String headerName, long date) {
 	 * @param headerName the header name
 	 * @return the parsed date header, or -1 if none
 	 * @since 3.2.4
+	 * @see #getFirstZonedDateTime(String)
 	 */
 	public long getFirstDate(String headerName) {
 		return getFirstDate(headerName, true);
@@ -1210,32 +1228,69 @@ public long getFirstDate(String headerName) {
 	 * {@link IllegalArgumentException} ({@code true}) or rather return -1
 	 * in that case ({@code false})
 	 * @return the parsed date header, or -1 if none (or invalid)
- 	 */
+	 * @see #getFirstZonedDateTime(String, boolean)
+	 */
 	private long getFirstDate(String headerName, boolean rejectInvalid) {
+		ZonedDateTime zonedDateTime = getFirstZonedDateTime(headerName, rejectInvalid);
+		return (zonedDateTime != null ? zonedDateTime.toInstant().toEpochMilli() : -1);
+	}
+
+	/**
+	 * Parse the first header value for the given header name as a date,
+	 * return {@code null} if there is no value, or raise {@link IllegalArgumentException}
+	 * if the value cannot be parsed as a date.
+	 * @param headerName the header name
+	 * @return the parsed date header, or {@code null} if none
+	 * @since 5.0
+	 */
+	@Nullable
+	public ZonedDateTime getFirstZonedDateTime(String headerName) {
+		return getFirstZonedDateTime(headerName, true);
+	}
+
+	/**
+	 * Parse the first header value for the given header name as a date,
+	 * return {@code null} if there is no value or also in case of an invalid value
+	 * (if {@code rejectInvalid=false}), or raise {@link IllegalArgumentException}
+	 * if the value cannot be parsed as a date.
+	 * @param headerName the header name
+	 * @param rejectInvalid whether to reject invalid values with an
+	 * {@link IllegalArgumentException} ({@code true}) or rather return {@code null}
+	 * in that case ({@code false})
+	 * @return the parsed date header, or {@code null} if none (or invalid)
+ 	 */
+	@Nullable
+	private ZonedDateTime getFirstZonedDateTime(String headerName, boolean rejectInvalid) {
 		String headerValue = getFirst(headerName);
 		if (headerValue == null) {
 			// No header value sent at all
-			return -1;
+			return null;
 		}
 		if (headerValue.length() >= 3) {
 			// Short "0" or "-1" like values are never valid HTTP date headers...
-			// Let's only bother with SimpleDateFormat parsing for long enough values.
-			for (String dateFormat : DATE_FORMATS) {
-				SimpleDateFormat simpleDateFormat = new SimpleDateFormat(dateFormat, Locale.US);
-				simpleDateFormat.setTimeZone(GMT);
+			// Let's only bother with DateTimeFormatter parsing for long enough values.
+
+			// See https://stackoverflow.com/questions/12626699/if-modified-since-http-header-passed-by-ie9-includes-length
+			int parametersIndex = headerValue.indexOf(";");
+			if (parametersIndex != -1) {
+				headerValue = headerValue.substring(0, parametersIndex);
+			}
+
+			for (DateTimeFormatter dateFormatter : DATE_FORMATTERS) {
 				try {
-					return simpleDateFormat.parse(headerValue).getTime();
+					return ZonedDateTime.parse(headerValue, dateFormatter);
 				}
-				catch (ParseException ex) {
+				catch (DateTimeParseException ex) {
 					// ignore
 				}
 			}
+
 		}
 		if (rejectInvalid) {
 			throw new IllegalArgumentException("Cannot parse date value \"" + headerValue +
 					"\" for \"" + headerName + "\" header");
 		}
-		return -1;
+		return null;
 	}
 
 	/**

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

@@ -21,6 +21,8 @@
 import java.net.URISyntaxException;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Calendar;
@@ -34,6 +36,7 @@
 import org.hamcrest.Matchers;
 import org.junit.Test;
 
+import static java.time.format.DateTimeFormatter.*;
 import static org.hamcrest.Matchers.is;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -466,4 +469,40 @@ public void contentLanguageSerialized() {
 		assertEquals("Expected one (first) locale", Locale.GERMAN, headers.getContentLanguage());
 	}
 
+	@Test
+	public void firstDate() {
+		headers.setDate(HttpHeaders.DATE, 1229595600000L);
+		assertThat(headers.getFirstDate(HttpHeaders.DATE), is(1229595600000L));
+
+		headers.clear();
+
+		headers.add(HttpHeaders.DATE, "Thu, 18 Dec 2008 10:20:00 GMT");
+		headers.add(HttpHeaders.DATE, "Sat, 18 Dec 2010 10:20:00 GMT");
+		assertThat(headers.getFirstDate(HttpHeaders.DATE), is(1229595600000L));
+	}
+
+	@Test
+	public void firstZonedDateTime() {
+		ZonedDateTime date = ZonedDateTime.of(2017, 6, 22, 22, 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"));
+		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));
+		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");
+		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");
+		assertTrue(headers.getFirstZonedDateTime(HttpHeaders.DATE).isEqual(date));
+	}
+
 }

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

@@ -115,7 +115,7 @@ public void headers() throws URISyntaxException {
 
 		assertEquals("text/plain", responseHeaders.getFirst("Accept"));
 		assertEquals("utf-8", responseHeaders.getFirst("Accept-Charset"));
-		assertEquals("Thu, 01 Jan 1970 00:00:12 GMT", responseHeaders.getFirst("If-Modified-Since"));
+		assertEquals("Thu, 1 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/ResponseEntityTests.java

@@ -160,7 +160,7 @@ public void headers() throws URISyntaxException {
 		HttpHeaders responseHeaders = responseEntity.getHeaders();
 
 		assertEquals("GET", responseHeaders.getFirst("Allow"));
-		assertEquals("Thu, 01 Jan 1970 00:00:12 GMT",
+		assertEquals("Thu, 1 Jan 1970 00:00:12 GMT",
 				responseHeaders.getFirst("Last-Modified"));
 		assertEquals(location.toASCIIString(),
 				responseHeaders.getFirst("Location"));

spring-webflux/src/main/java/org/springframework/web/reactive/function/server/DefaultServerResponseBuilder.java

@@ -125,9 +125,7 @@ public ServerResponse.BodyBuilder hint(String key, Object value) {
 
 	@Override
 	public ServerResponse.BodyBuilder lastModified(ZonedDateTime lastModified) {
-		ZonedDateTime gmt = lastModified.withZoneSameInstant(ZoneId.of("GMT"));
-		String headerValue = DateTimeFormatter.RFC_1123_DATE_TIME.format(gmt);
-		this.headers.set(HttpHeaders.LAST_MODIFIED, headerValue);
+		this.headers.setZonedDateTime(HttpHeaders.LAST_MODIFIED, lastModified);
 		return this;
 	}