refactor: combine Thymeleaf error pages into one.

Fix #1119

Author: mukeshk

src/main/java/ru/mystamps/web/config/MvcConfig.java

@@ -105,7 +105,7 @@ public void configureDefaultServletHandling(DefaultServletHandlerConfigurer conf
 	@Override
 	public void addViewControllers(ViewControllerRegistry registry) {
 		registry.addViewController(AccountUrl.AUTHENTICATION_PAGE);
-		registry.addViewController(SiteUrl.FORBIDDEN_PAGE);
+		registry.addViewController(SiteUrl.FORBIDDEN_PAGE).setViewName("error/status-code");
 	}
 
 	@Override

src/main/java/ru/mystamps/web/feature/site/ErrorController.java

@@ -37,7 +37,7 @@ public class ErrorController {
 	private final SiteService siteService;
 
 	@RequestMapping(SiteUrl.NOT_FOUND_PAGE)
-	public void notFound(
+	public String notFound(
 			HttpServletRequest request,
 			@CurrentUser Integer currentUserId,
 			// CheckStyle: ignore LineLength for next 1 line
@@ -50,10 +50,12 @@ public void notFound(
 		String method = request.getMethod();
 
 		siteService.logAboutAbsentPage(page, method, currentUserId, ip, referer, agent);
+		
+		return "error/status-code";
 	}
 
 	@RequestMapping(SiteUrl.INTERNAL_ERROR_PAGE)
-	public void internalError(
+	public String internalError(
 		// CheckStyle: ignore LineLength for next 3 lines
 		@RequestAttribute(name = RequestDispatcher.ERROR_EXCEPTION_TYPE, required = false) Class<?> exceptionType,
 		@RequestAttribute(name = RequestDispatcher.ERROR_EXCEPTION, required = false) Exception exception,
@@ -69,6 +71,7 @@ public void internalError(
 				exception
 			);
 		}
+		return "error/status-code";
 	}
 
 	private static Object getNameOrAsIs(Class<?> clazz) {

src/main/resources/ru/mystamps/i18n/Messages.properties

@@ -96,15 +96,11 @@ t_password_again = Retype password
 t_activation_key = Activation key
 t_register = Register
 
-# error/403.html
+# error/status-code.html
 t_403_title = 403: forbidden
 t_403_description = Forbidden
-
-# error/404.html
 t_404_title = 404: page not found
 t_404_description = Requested page{0}not found
-
-# error/500.html
 t_500_title = 500: internal server error
 t_500_description = Internal{0}server error
 

src/main/resources/ru/mystamps/i18n/Messages_ru.properties

@@ -96,15 +96,11 @@ t_password_again = Пароль (ещё раз)
 t_activation_key = Код активации
 t_register = Зарегистрироваться
 
-# error/403.html
+# error/status-code.html
 t_403_title = 403: доступ запрещён
 t_403_description = Доступ запрещён
-
-# error/404.html
 t_404_title = 404: страница не найдена
 t_404_description = Запрашиваемая страница{0}не найдена
-
-# error/500.html
 t_500_title = 500: внутренняя ошибка сервера
 t_500_description = Внутренняя{0}ошибка сервера
 

src/main/webapp/WEB-INF/views/error/403.html

@@ -8,7 +8,13 @@
 		<meta name="viewport" content="width=device-width, initial-scale=1.0" />
 		<meta http-equiv="X-UA-Compatible" content="IE=edge" />
 		<meta name="robots" content="noindex" />
-		<title th:text="#{t_500_title}">500: internal server error</title>
+		<!--/*/
+			<th:block th:switch="${#response.status}">
+			<title th:case="'403'" th:text="#{t_403_title}">403: forbidden</title>
+			<title th:case="'404'" th:text="#{t_404_title}">404: page not found</title>
+		/*/-->
+		<title th:case="'500'" th:text="#{t_500_title}">500: internal server error</title>
+		<!--/*/ </th:block> /*/-->
 		<link rel="shortcut icon" type="image/x-icon" href="../../../favicon.ico" th:href="${FAVICON_ICO}" />
 		<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" th:href="${BOOTSTRAP_CSS}" />
 		<link rel="stylesheet" href="../../static/styles/main.css" th:href="${MAIN_CSS}" />
@@ -53,11 +59,21 @@
 
 			<div class="row text-center">
 				<div id="content" class="col-sm-12">
-					<h1 id="error-code">
+					<h1 id="error-code" th:text="${#response.status}">
 						500
 					</h1>
-					<h4 id="error-msg" th:utext="#{t_500_description('&lt;br /&gt;')}">
-						Internal<br />server error
+					<h4 id="error-msg" th:switch="${#response.status}">
+						<!--/*/
+						<span th:case="'403'" th:text="#{t_403_description}" th:remove="tag">
+							Forbidden
+						</span>
+						<span th:case="'404'" th:utext="#{t_404_description('&lt;br /&gt;')}" th:remove="tag">
+							Requested page<br />not found
+						</span>
+						/*/-->
+						<span th:case="*" th:utext="#{t_500_description('&lt;br /&gt;')}" th:remove="tag">
+							Internal<br />server error
+						</span>
 					</h4>
 				</div>
 			</div>