Multi File upload can be done any way you like in Liferay 6.2 since the platform let's you write any code you want. However, there is an entire SDK ( Java and JavaScript ), amd a bunch of taglibs that make it easier. Here is the best example of a multi uploader you can find, done the Liferay way, modified from the portals source code

multiupload.jsf

<%@page import="com.liferay.portlet.PortletURLFactoryUtil"%>
<%@ include file="../init.jsp"%>


<liferay-portlet:resourceURL copyCurrentRenderParameters="<%= false %>" var="uploadMultipleFileEntries">
	<portlet:param name="struts_action" value="/document_library/upload_multiple_file_entries" />
	<portlet:param name="repositoryId" value="<%=  String.valueOf(themeDisplay.getScopeGroupId())%>" />
	<portlet:param name="folderId" value="0" />
</liferay-portlet:resourceURL>

<portlet:actionURL var="uploadMultipleFileEntriesURL">
	<portlet:param name="struts_action" value="document_library/upload_multiple_file_entries" />
	<portlet:param name="backURL" value='<%= PortletURLFactoryUtil.create(renderRequest, themeDisplay.getPortletDisplay().getId(), themeDisplay.getLayout().getPlid(), "RENDER_PHASE").toString() %>' />
</portlet:actionURL>

<c:choose>
	<c:when test="<%= true %>">
		<aui:row>
			<aui:col width="70">
				<aui:form name="fm1">
					<div class="lfr-dynamic-uploader">
						<div class="lfr-upload-container" id="<portlet:namespace />fileUpload"></div>
					</div>
				</aui:form>

				<%
				Date expirationDate = new Date(System.currentTimeMillis() + 30 * Time.MINUTE);

				Ticket ticket = TicketLocalServiceUtil.addTicket(user.getCompanyId(), User.class.getName(), user.getUserId(), TicketConstants.TYPE_IMPERSONATE, null, expirationDate, new ServiceContext());
				%>

				<aui:script use="liferay-upload">
					new Liferay.Upload(
						{
							boundingBox: '#<portlet:namespace />fileUpload',
							deleteFile: '<liferay-portlet:actionURL doAsUserId="<%= user.getUserId() %>"><portlet:param name="struts_action" value="/document_library/upload_multiple_file_entries" /><portlet:param name="<%= Constants.CMD %>" value="<%= Constants.DELETE_TEMP %>" /><portlet:param name="folderId" value="<%= String.valueOf(DLFolderConstants.DEFAULT_PARENT_FOLDER_ID) %>" /></liferay-portlet:actionURL>&ticketKey=<%= ticket.getKey() %><liferay-ui:input-permissions-params modelName="com.liferay.portlet.documentlibrary.model.DLFileEntryConstants" />',
							fileDescription: '<%= StringUtil.merge(PrefsPropsUtil.getStringArray(RequestConstants.FILE_VALID_EXT, StringPool.COMMA)) %>',
							maxFileSize: '<%= String.valueOf(PrefsPropsUtil.getLong(RequestConstants.FILE_VALID_SIZE)) %>',
							namespace: '<portlet:namespace />',
							tempFileURL: {
								method: Liferay.Service.bind('/dlapp/get-temp-file-entry-names'),
								params: {
									groupId: <%= themeDisplay.getScopeGroupId() %>,
									folderId: <%= DLFolderConstants.DEFAULT_PARENT_FOLDER_ID %>,
									tempFolderName: 'com.liferay.portlet.documentlibrary.action.EditFileEntryAction'
								}
							},
							tempRandomSuffix: '--tempRandomSuffix--',
							uploadFile: '<liferay-portlet:actionURL doAsUserId="<%= user.getUserId() %>"><portlet:param name="struts_action" value="/document_library/upload_multiple_file_entries" /><portlet:param name="<%= Constants.CMD %>" value="<%= Constants.ADD_TEMP %>" /><portlet:param name="folderId" value="0" /></liferay-portlet:actionURL>&ticketKey=<%= ticket.getKey() %>'
						}
					);
				</aui:script>
			</aui:col>
			<aui:col width="30">
				<div class="common-file-metadata-container selected" id="<portlet:namespace />commonFileMetadataContainer">
					<aui:form method="post" action="<%=uploadMultipleFileEntriesURL %>" name="fm2"  onSubmit='<%="event.preventDefault(); " + liferayPortletResponse.getNamespace() + "updateMultipleFiles();" %>'>
						<aui:input name="<%= Constants.CMD %>" type="hidden" value="<%= Constants.ADD_MULTIPLE %>" />
						<aui:input name="repositoryId" type="hidden" value="<%= String.valueOf(themeDisplay.getScopeGroupId()) %>" />
						<aui:input name="folderId" type="hidden" value="0" />
						<div class="no-files-selected-info alert alert-info hide" id="<portlet:namespace />metadataExplanationContainer">
							<liferay-ui:message key="select-documents-from-the-left-to-add-them-to-the-documents-and-media" />
						</div>
					
						<liferay-ui:panel-container extended="<%= false %>" id="documentLibraryAssetPanelContainer" persistState="<%= true %>">
							<div class="selected-files-count">
								<liferay-ui:message key="no-files-selected" />
							</div>
						</liferay-ui:panel-container>
					
						<span id="<portlet:namespace />selectedFileNameContainer"></span>
					
						<aui:button type="submit" value="Save" cssClass="" />
					</aui:form>
				</div>
				<aui:script>
				Liferay.provide(window, '<portlet:namespace />updateMultipleFiles',
						function() {
							var A = AUI();
							var Lang = A.Lang;

							var commonFileMetadataContainer = A.one('#<portlet:namespace />commonFileMetadataContainer');
							var selectedFileNameContainer = A.one('#<portlet:namespace />selectedFileNameContainer');

							var inputTpl = '<input id="<portlet:namespace />selectedFileName{0}" name="<portlet:namespace />selectedFileName" type="hidden" value="{1}" />';

							var values = A.all('input[name=<portlet:namespace />selectUploadedFileCheckbox]:checked').val();

							var buffer = [];
							var dataBuffer = [];
							var length = values.length;

							for (var i = 0; i < length; i++) {
								dataBuffer[0] = i;
								dataBuffer[1] = values[i];

								buffer[i] = Lang.sub(inputTpl, dataBuffer);
							}

							selectedFileNameContainer.html(buffer.join(''));

							commonFileMetadataContainer.plug(A.LoadingMask);

							commonFileMetadataContainer.loadingmask.show();

							A.io.request(
								document.<portlet:namespace />fm2.action,
								{
									dataType: 'json',
									form: {
										id: document.<portlet:namespace />fm2
									},
									after: {
										success: function(event, id, obj) {
											var items = A.all('input[data-fileName]');
											console.log(items);
											for (var i = 0; i < items.size(); i++) {
												var item = item.get(i);
												var li = item.ancestor();

												item.remove(true);

												li.removeClass('selectable').removeClass('selected');

												var cssClass = null;
												var childHTML = null;

												if (item.added) {
													cssClass = 'file-saved';

													var originalFileName = item;

													var pos = originalFileName.indexOf('--tempRandomSuffix--');

													if (pos != -1) {
														originalFileName = originalFileName.substr(0, pos);
													}

													if (originalFileName === item.fileName) {
														childHTML = '<span class="success-message"><%= UnicodeLanguageUtil.get(pageContext, "successfully-saved") %></span>';
													}
													else {
														childHTML = '<span class="success-message"><%= UnicodeLanguageUtil.get(pageContext, "successfully-saved") %> (' + item.fileName + ')</span>';
													}
												}
												else {
													cssClass = 'upload-error';

													childHTML = '<span class="error-message">' + item.errorMessage + '</span>';
												}

												li.addClass(cssClass);
												li.append(childHTML);
											}

	

											if (commonFileMetadataContainer.io) {
												commonFileMetadataContainer.io.start();
											}
											else {
												commonFileMetadataContainer.load('<%= uploadMultipleFileEntries %>');
											}

											Liferay.fire('filesSaved');
										},
										failure: function(event, id, obj) {
											var selectedItems = A.all('#<portlet:namespace />fileUpload li.selected');

											selectedItems.removeClass('selectable').removeClass('selected').addClass('upload-error');

											selectedItems.append('<span class="error-message"><%= UnicodeLanguageUtil.get(pageContext, "an-unexpected-error-occurred-while-deleting-the-file") %></span>');

											selectedItems.all('input').remove(true);

											commonFileMetadataContainer.loadingmask.hide();
										}
									}
								}
							);
						},
						['aui-base']
					);
				</aui:script>
				
			</aui:col>
		</aui:row>
	</c:when>
	
	<c:otherwise>
		<div class="alert alert-error">
			<liferay-ui:message key="you-do-not-have-the-required-permissions-to-access-this-application" />
		</div>
	</c:otherwise>
	
</c:choose>