Adds support to use Struts' Locale

plugins/tiles/src/main/java/org/apache/struts2/tiles/StrutsTilesContainerFactory.java

@@ -161,6 +161,10 @@ public class StrutsTilesContainerFactory extends BasicTilesContainerFactory {
         return resolver;
     }
 
+    protected LocaleResolver createLocaleResolver(ApplicationContext applicationContext) {
+        return new StrutsTilesLocaleResolver();
+    }
+
     @Override
     protected List<ApplicationResource> getSources(ApplicationContext applicationContext) {
         Collection<ApplicationResource> resources = applicationContext.getResources(getTilesDefinitionPattern(applicationContext.getInitParams()));

plugins/tiles/src/main/java/org/apache/struts2/tiles/StrutsTilesLocaleResolver.java

@@ -0,0 +1,54 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.struts2.tiles;
+
+import com.opensymphony.xwork2.ActionContext;
+import com.opensymphony.xwork2.LocaleProvider;
+import com.opensymphony.xwork2.config.ConfigurationException;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.apache.struts2.ServletActionContext;
+import org.apache.tiles.locale.LocaleResolver;
+import org.apache.tiles.request.Request;
+import org.apache.tiles.request.servlet.ServletUtil;
+
+import javax.servlet.http.HttpServletRequest;
+import java.util.Locale;
+
+public class StrutsTilesLocaleResolver implements LocaleResolver {
+
+    private static Logger LOG = LogManager.getLogger(StrutsTilesLocaleResolver.class);
+
+    @Override
+    public Locale resolveLocale(Request request) {
+        HttpServletRequest httpRequest = ServletUtil.getServletRequest(request).getRequest();
+        ActionContext ctx = ServletActionContext.getActionContext(httpRequest);
+
+        if (ctx == null) {
+            LOG.error("Cannot obtain HttpServletRequest from [{}]", request.getClass().getName());
+            throw new ConfigurationException("There is no ActionContext for current request!");
+        }
+
+        LocaleProvider provider = ctx.getInstance(LocaleProvider.class);
+
+        return provider.getLocale();
+    }
+
+}