Consistent evaluation of empty theme names to default theme name

Issue: SPR-11128
(cherry picked from commit cc81aae)

Author: jhoeller

spring-webmvc/src/main/java/org/springframework/web/servlet/theme/CookieThemeResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -20,12 +20,13 @@
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.springframework.util.StringUtils;
 import org.springframework.web.servlet.ThemeResolver;
 import org.springframework.web.util.CookieGenerator;
 import org.springframework.web.util.WebUtils;
 
 /**
- * Implementation of ThemeResolver that uses a cookie sent back to the user
+ * {@link ThemeResolver} implementation that uses a cookie sent back to the user
  * in case of a custom setting, with a fallback to the default theme.
  * This is particularly useful for stateless applications without user sessions.
  *
@@ -78,28 +79,34 @@ public String getDefaultThemeName() {
 
 	public String resolveThemeName(HttpServletRequest request) {
 		// Check request for preparsed or preset theme.
-		String theme = (String) request.getAttribute(THEME_REQUEST_ATTRIBUTE_NAME);
-		if (theme != null) {
-			return theme;
+		String themeName = (String) request.getAttribute(THEME_REQUEST_ATTRIBUTE_NAME);
+		if (themeName != null) {
+			return themeName;
 		}
 
 		// Retrieve cookie value from request.
 		Cookie cookie = WebUtils.getCookie(request, getCookieName());
 		if (cookie != null) {
-			return cookie.getValue();
+			String value = cookie.getValue();
+			if (StringUtils.hasText(value)) {
+				themeName = value;
+			}
 		}
 
 		// Fall back to default theme.
-		return getDefaultThemeName();
+		if (themeName == null) {
+			themeName = getDefaultThemeName();
+		}
+		request.setAttribute(THEME_REQUEST_ATTRIBUTE_NAME, themeName);
+		return themeName;
 	}
 
 	public void setThemeName(HttpServletRequest request, HttpServletResponse response, String themeName) {
-		if (themeName != null) {
+		if (StringUtils.hasText(themeName)) {
 			// Set request attribute and add cookie.
 			request.setAttribute(THEME_REQUEST_ATTRIBUTE_NAME, themeName);
 			addCookie(response, themeName);
 		}
-
 		else {
 			// Set request attribute to fallback theme and remove cookie.
 			request.setAttribute(THEME_REQUEST_ATTRIBUTE_NAME, getDefaultThemeName());

spring-webmvc/src/main/java/org/springframework/web/servlet/theme/SessionThemeResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -19,12 +19,14 @@
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
+import org.springframework.util.StringUtils;
 import org.springframework.web.util.WebUtils;
 
 /**
- * Implementation of ThemeResolver that uses a theme attribute in the user's
- * session in case of a custom setting, with a fallback to the default theme.
- * This is most appropriate if the application needs user sessions anyway.
+ * {@link org.springframework.web.servlet.ThemeResolver} implementation that
+ * uses a theme attribute in the user's session in case of a custom setting,
+ * with a fallback to the default theme. This is most appropriate if the
+ * application needs user sessions anyway.
  *
  * <p>Custom controllers can override the user's theme by calling
  * {@code setThemeName}, e.g. responding to a theme change request.
@@ -46,14 +48,16 @@ public class SessionThemeResolver extends AbstractThemeResolver {
 	 */
 	public static final String THEME_SESSION_ATTRIBUTE_NAME = SessionThemeResolver.class.getName() + ".THEME";
 
+
 	public String resolveThemeName(HttpServletRequest request) {
-		String theme = (String) WebUtils.getSessionAttribute(request, THEME_SESSION_ATTRIBUTE_NAME);
-		// specific theme, or fallback to default?
-		return (theme != null ? theme : getDefaultThemeName());
+		String themeName = (String) WebUtils.getSessionAttribute(request, THEME_SESSION_ATTRIBUTE_NAME);
+		// A specific theme indicated, or do we need to fallback to the default?
+		return (themeName != null ? themeName : getDefaultThemeName());
 	}
 
 	public void setThemeName(HttpServletRequest request, HttpServletResponse response, String themeName) {
-		WebUtils.setSessionAttribute(request, THEME_SESSION_ATTRIBUTE_NAME, themeName);
+		WebUtils.setSessionAttribute(request, THEME_SESSION_ATTRIBUTE_NAME,
+				(StringUtils.hasText(themeName) ? themeName : null));
 	}
 
 }