Uses better class resolver logic

Author: lukaszlenart

core/src/main/java/org/apache/struts2/views/freemarker/FreemarkerManager.java

@@ -34,6 +34,7 @@
 import freemarker.cache.MultiTemplateLoader;
 import freemarker.cache.TemplateLoader;
 import freemarker.cache.WebappTemplateLoader;
+import freemarker.core.TemplateClassResolver;
 import freemarker.ext.jsp.TaglibFactory;
 import freemarker.ext.servlet.HttpRequestHashModel;
 import freemarker.ext.servlet.HttpRequestParametersHashModel;
@@ -344,6 +345,9 @@ protected Configuration createConfiguration(ServletContext servletContext) throw
         configuration.setLocalizedLookup(false);
         configuration.setWhitespaceStripping(true);
 
+        LOG.debug("Sets NewBuiltinClassResolver to TemplateClassResolver.SAFER_RESOLVER");
+        configuration.setNewBuiltinClassResolver(TemplateClassResolver.SAFER_RESOLVER);
+
         return configuration;
     }