MockHttpServletResponse.getDateHeader returns -1 for non-existent header

Includes consistent getDateHeader results in both MockHttpServletResponse variants (spring-test and spring-web)

Issue: SPR-16160

Author: jhoeller

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

@@ -23,6 +23,7 @@
 import java.io.PrintWriter;
 import java.io.UnsupportedEncodingException;
 import java.io.Writer;
+import java.text.DateFormat;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.ArrayList;
@@ -517,27 +518,33 @@ public void setDateHeader(String name, long value) {
 		setHeaderValue(name, formatDate(value));
 	}
 
+	@Override
+	public void addDateHeader(String name, long value) {
+		addHeaderValue(name, formatDate(value));
+	}
+
 	public long getDateHeader(String name) {
-		SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT, Locale.US);
-		dateFormat.setTimeZone(GMT);
+		String headerValue = getHeader(name);
+		if (headerValue == null) {
+			return -1;
+		}
 		try {
-			return dateFormat.parse(getHeader(name)).getTime();
+			return newDateFormat().parse(getHeader(name)).getTime();
 		}
 		catch (ParseException ex) {
 			throw new IllegalArgumentException(
-					"Value for header '" + name + "' is not a valid Date: " + getHeader(name));
+					"Value for header '" + name + "' is not a valid Date: " + headerValue);
 		}
 	}
 
-	@Override
-	public void addDateHeader(String name, long value) {
-		addHeaderValue(name, formatDate(value));
+	private String formatDate(long date) {
+		return newDateFormat().format(new Date(date));
 	}
 
-	private String formatDate(long date) {
+	private DateFormat newDateFormat() {
 		SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT, Locale.US);
 		dateFormat.setTimeZone(GMT);
-		return dateFormat.format(new Date(date));
+		return dateFormat;
 	}
 
 	@Override

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

@@ -291,6 +291,12 @@ public void getInvalidDateHeader() {
 		response.getDateHeader("Last-Modified");
 	}
 
+	@Test  // SPR-16160
+	public void getNonExistentDateHeader() {
+		assertNull(response.getHeader("Last-Modified"));
+		assertEquals(-1, response.getDateHeader("Last-Modified"));
+	}
+
 	@Test  // SPR-10414
 	public void modifyStatusAfterSendError() throws IOException {
 		response.sendError(HttpServletResponse.SC_NOT_FOUND);

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

@@ -23,16 +23,17 @@
 import java.io.PrintWriter;
 import java.io.UnsupportedEncodingException;
 import java.io.Writer;
-import java.time.Instant;
-import java.time.ZoneId;
-import java.time.ZonedDateTime;
-import java.time.format.DateTimeParseException;
+import java.text.DateFormat;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Date;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.TimeZone;
 import javax.servlet.ServletOutputStream;
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletResponse;
@@ -44,8 +45,6 @@
 import org.springframework.util.StringUtils;
 import org.springframework.web.util.WebUtils;
 
-import static java.time.format.DateTimeFormatter.*;
-
 /**
  * Mock implementation of the {@link javax.servlet.http.HttpServletResponse} interface.
  *
@@ -60,7 +59,9 @@ public class MockHttpServletResponse implements HttpServletResponse {
 
 	private static final String CHARSET_PREFIX = "charset=";
 
-	private static final ZoneId GMT = ZoneId.of("GMT");
+	private static final String DATE_FORMAT = "EEE, dd MMM yyyy HH:mm:ss zzz";
+
+	private static final TimeZone GMT = TimeZone.getTimeZone("GMT");
 
 
 	//---------------------------------------------------------------------
@@ -292,7 +293,7 @@ public void reset() {
 		this.characterEncoding = null;
 		this.contentLength = 0;
 		this.contentType = null;
-		this.locale = null;
+		this.locale = Locale.getDefault();
 		this.cookies.clear();
 		this.headers.clear();
 		this.status = HttpServletResponse.SC_OK;
@@ -302,9 +303,7 @@ public void reset() {
 	@Override
 	public void setLocale(Locale locale) {
 		this.locale = locale;
-		if (locale != null) {
-			doAddHeaderValue(HttpHeaders.ACCEPT_LANGUAGE, locale.toLanguageTag(), true);
-		}
+		doAddHeaderValue(HttpHeaders.ACCEPT_LANGUAGE, locale.toLanguageTag(), true);
 	}
 
 	@Override
@@ -507,25 +506,33 @@ public void setDateHeader(String name, long value) {
 		setHeaderValue(name, formatDate(value));
 	}
 
+	@Override
+	public void addDateHeader(String name, long value) {
+		addHeaderValue(name, formatDate(value));
+	}
+
 	public long getDateHeader(String name) {
+		String headerValue = getHeader(name);
+		if (headerValue == null) {
+			return -1;
+		}
 		try {
-			return ZonedDateTime.parse(getHeader(name), RFC_1123_DATE_TIME).toInstant().toEpochMilli();
+			return newDateFormat().parse(getHeader(name)).getTime();
 		}
-		catch (DateTimeParseException ex) {
+		catch (ParseException ex) {
 			throw new IllegalArgumentException(
-					"Value for header '" + name + "' is not a valid Date: " + getHeader(name));
+					"Value for header '" + name + "' is not a valid Date: " + headerValue);
 		}
 	}
 
-	@Override
-	public void addDateHeader(String name, long value) {
-		addHeaderValue(name, formatDate(value));
+	private String formatDate(long date) {
+		return newDateFormat().format(new Date(date));
 	}
 
-	private String formatDate(long date) {
-		Instant instant = Instant.ofEpochMilli(date);
-		ZonedDateTime zonedDateTime = ZonedDateTime.ofInstant(instant, GMT);
-		return RFC_1123_DATE_TIME.format(zonedDateTime);
+	private DateFormat newDateFormat() {
+		SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT, Locale.US);
+		dateFormat.setTimeZone(GMT);
+		return dateFormat;
 	}
 
 	@Override
@@ -576,7 +583,7 @@ else if (HttpHeaders.ACCEPT_LANGUAGE.equalsIgnoreCase(name)) {
 			HttpHeaders headers = new HttpHeaders();
 			headers.add(HttpHeaders.ACCEPT_LANGUAGE, value.toString());
 			List<Locale> locales = headers.getAcceptLanguageAsLocales();
-			setLocale(locales.isEmpty() ? null : locales.get(0));
+			this.locale = (!locales.isEmpty() ? locales.get(0) : Locale.getDefault());
 			return true;
 		}
 		else {