Bug 4032: Initial implementation of a filter that transfers a user's

preferred language using a Cookie

java/com.sap.sailing.dashboards.gwt/WEB-INF/web.xml

@@ -28,6 +28,15 @@
 		<url-pattern>/service/sailing</url-pattern>
 	</servlet-mapping>
 
+	<filter>
+		<filter-name>LocaleInjectionFilter</filter-name>
+		<filter-class>com.sap.sse.security.ui.server.LocaleInjectionFilter</filter-class>
+	</filter>
+	<filter-mapping>
+		<filter-name>LocaleInjectionFilter</filter-name>
+		<url-pattern>*.html</url-pattern>
+	</filter-mapping>
+
 	<servlet>
 		<display-name>Dashboard Dispatch Service</display-name>
 		<servlet-name>dashboardDispatch</servlet-name>

java/com.sap.sailing.gwt.ui/WEB-INF/web.xml

@@ -53,6 +53,15 @@
 		<url-pattern>/*</url-pattern>
 	</filter-mapping>
 
+	<filter>
+		<filter-name>LocaleInjectionFilter</filter-name>
+		<filter-class>com.sap.sse.security.ui.server.LocaleInjectionFilter</filter-class>
+	</filter>
+	<filter-mapping>
+		<filter-name>LocaleInjectionFilter</filter-name>
+		<url-pattern>*.html</url-pattern>
+	</filter-mapping>
+
 	<servlet>
 	    <display-name>Sailing Service</display-name>
 	    <servlet-name>SailingService</servlet-name>

java/com.sap.sse.security.ui/WEB-INF/web.xml

@@ -44,6 +44,15 @@
 		<dispatcher>ERROR</dispatcher>
 	</filter-mapping>
 
+	<filter>
+		<filter-name>LocaleInjectionFilter</filter-name>
+		<filter-class>com.sap.sse.security.ui.server.LocaleInjectionFilter</filter-class>
+	</filter>
+	<filter-mapping>
+		<filter-name>LocaleInjectionFilter</filter-name>
+		<url-pattern>*.html</url-pattern>
+	</filter-mapping>
+
 	<servlet>
 		<display-name>User Management Service</display-name>
 		<servlet-name>UserManagementService</servlet-name>

java/com.sap.sse.security.ui/src/main/java/com/sap/sse/security/ui/server/LocaleInjectionFilter.java

@@ -0,0 +1,77 @@
+package com.sap.sse.security.ui.server;
+
+import java.io.IOException;
+import java.util.Locale;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.FilterConfig;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.http.Cookie;
+import javax.servlet.http.HttpServletResponse;
+
+import org.apache.shiro.SecurityUtils;
+import org.apache.shiro.subject.Subject;
+import org.osgi.framework.BundleContext;
+import org.osgi.util.tracker.ServiceTracker;
+
+import com.sap.sse.security.SecurityService;
+import com.sap.sse.security.User;
+
+/**
+ * {@link Filter ServletFilter} implementation that sets a short living {@link Cookie} that carries a user's preferred
+ * locale if one is logged in. This allows the GWT UI to be shown in the user's preferred language without the need to
+ * rewrite the URL with the locale parameter added. This also ensures that shared URLs are locale-independent unless a
+ * user manually selects a specific locale for a page.
+ */
+public class LocaleInjectionFilter implements Filter {
+    private ServiceTracker<SecurityService, SecurityService> securityServiceTracker;
+
+    @Override
+    public void init(FilterConfig filterConfig) throws ServletException {
+    }
+
+    @Override
+    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
+            throws IOException, ServletException {
+        if (securityServiceTracker == null) {
+            // It would be preferable to do this in init, but somehow, the context is sometimes null
+            final BundleContext context = Activator.getContext();
+            securityServiceTracker = new ServiceTracker<>(context, SecurityService.class, /* customizer */ null);
+            securityServiceTracker.open();
+        }
+        
+        final HttpServletResponse resp = (HttpServletResponse) response;
+        final Subject currentSubject = SecurityUtils.getSubject();
+        if (currentSubject != null) {
+            final Object principal = currentSubject.getPrincipal();
+            if (principal instanceof String) {
+                final SecurityService service = securityServiceTracker.getService();
+                if (service != null) {
+                    final User user = service.getUserByName((String) principal);
+                    if (user != null) {
+                        final Locale preferredLocale = user.getLocale();
+                        if (preferredLocale != null) {
+                            final Cookie cookie = new Cookie(UserManagementConstants.LOCALE_COOKIE_NAME,
+                                    preferredLocale.toLanguageTag());
+                            cookie.setMaxAge(-1);
+                            resp.addCookie(cookie);
+                        }
+                    }
+                }
+            }
+        }
+        chain.doFilter(request, response);
+    }
+
+    @Override
+    public void destroy() {
+        if (securityServiceTracker != null) {
+            securityServiceTracker.close();
+            securityServiceTracker = null;
+        }
+    }
+
+}

java/com.sap.sse.security.ui/src/main/java/com/sap/sse/security/ui/server/UserManagementConstants.java

@@ -0,0 +1,9 @@
+package com.sap.sse.security.ui.server;
+
+public interface UserManagementConstants {
+    /**
+     * Name of the Cookie to transfer a user's preferred language to the UI.
+     */
+    public static final String LOCALE_COOKIE_NAME = "GWT_LOCALE";
+
+}