Hi all,
DL Folder download size exceeds 10 GB then we need to display error message.
here we deloped the EditFolderMVCResourceCommand class hook like below.

@Component(
property = {
"javax.portlet.name=com_liferay_document_library_web_portlet_DLPortlet",
"javax.portlet.name=com_liferay_document_library_web_portlet_DLAdminPortlet",
"javax.portlet.name=com_liferay_document_library_web_portlet_IGDisplayPortlet",
"mvc.command.name=/document_library/edit_folder",
"service.ranking:Integer=100"
},
service = MVCResourceCommand.class
)
public class FolderDownloadResourceCommand implements MVCResourceCommand {


@Override
public boolean serveResource(ResourceRequest resourceRequest, ResourceResponse resourceResponse)
throws PortletException {
// TODO Auto-generated method stub
long repositoryId = ParamUtil.getLong(resourceRequest, "repositoryId");
long folderId = ParamUtil.getLong(resourceRequest, "folderId");

System.out.println(":::::::::***:::::FolderId"+folderId);
try {
double gbData = CommonUtil.getDownloadSize(repositoryId ,folderId, _dlAppService);
if(Validator.isNotNull(maxDownloadsize) && gbData < 10.0) {
mvcResourceCommand.serveResource (resourceRequest, resourceResponse);
}else {
System.out.println("Error message it's more than actual size"); // here it's entering but need to know how to display error message in screen
}

} catch (PortalException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return true;
}

@Reference(unbind = "-")
protected void setDLAppService(DLAppService dlAppService) {
_dlAppService = dlAppService;
}


@Reference(target = "(component.name=com.liferay.document.library.web.internal.portlet.action.EditFolderMVCResourceCommand)")
protected MVCResourceCommand mvcResourceCommand;

//private static final Log log = LogFactoryUtil.getLog(FolderDownloadResourceCommand.class);

@Reference
private DLAppService _dlAppService;
}

after enter above else condition then screen displaying blank

Please let me know how we want to do that?