Migrating from Vaadin 6 to Vaadin 7

For migration to Vaadin 7.1,  see Migrating From Vaadin 7.0 To Vaadin 7.1

Getting Started

Most Vaadin 7 APIs are compatible with Vaadin 6, but there are some changes that affect every application.

Moving to Vaadin 7 brings a number of features designed to make the lives of developers easier. It is a major version where we could improve (and break) some parts of the API that have been stagnant and in need of improvement for years.

Fear not, though, as the vast majority of the API is unchanged or practically so - many parts even for the last 10 years apart for some package name changes. While every application requires some migration steps, the minimal steps needed for many applications are simple enough, although a few more changes can be useful to benefit from some of the new features such as improvements to data binding.

The first step is to update Vaadin libraries. While Vaadin 6 had a single JAR and separate GWT JARs, Vaadin 7 is packaged as multiple JARs that also include GWT. The easiest way to get all you need is to use Ivy (see below in the section on updating an existing Eclipse project) or Maven (see below on updating a Maven project). If you are using the latest version of the Vaadin Eclipse plug-in, upgrading the facet version creates an Ivy configuration.

The first code change that applies to every Vaadin 6 application concerns the com.vaadin.Application class - it exists no more. The main entry point to your application is now a com.vaadin.ui.UI, which replaces Application and its main window. When switching to UI, you also get multi-window support out of the box, so bye bye to any old hacks to make it work. On the flip side, a new UI is created on page reload. If you prefer to keep the UI state over page reloads in the same way Vaadin 6 does, just add @PreserveOnRefresh annotation on your UI class.

For minimal migration, though, it is possible to replace Application with LegacyApplication and its main Window with LegacyWindow and postpone a little dealing with UIs, but when migrating to UIs, you get more out of the box. The class Window is now only used for "sub-windows" (windows floating inside the page) , not "browser level" windows or tabs (the whole web page).

An example should clarify things better than lengthy explanations, so:Vaadin 6:

package com.example.myexampleproject;

import com.vaadin.Application;
import com.vaadin.ui.*;

public class V6tm1Application extends Application {
  public void init() {
    Window mainWindow = new Window("V6tm1 Application");
    Label label = new Label("Hello Vaadin!");

Vaadin 7:

package com.example.myexampleproject;

import com.vaadin.server.VaadinRequest;
import com.vaadin.ui.*;

public class MyApplicationUI extends UI {

  protected void init(VaadinRequest request) {
    VerticalLayout view = new VerticalLayout();
    view.addComponent(new Label("Hello Vaadin!"));

In addition, replace com.vaadin.terminal.gwt.server.ApplicationServlet with com.vaadin.server.VaadinServlet in web.xml and its parameter "application" with "UI" pointing to your UI class, and the application is ready to go. Likewise, ApplicationPortlet has become VaadinPortlet.

Some package names have also been changed, but a simple import reorganization in your IDE should take care of this.

If you have a custom theme, import e.g. "../reindeer/legacy-styles.css" instead of "../reindeer/styles.css". The theme is now selected with an @Theme annotation on your UI class rather than a call to setTheme(), the usage should be clear from the example above.

Most remaining issues should show up as compilation errors and in most cases should be easy to fix in your IDE.

Now you should be ready to compile your widgetset (if any) and take the application for a first test drive. If you have customized themes, they will probably also need other updates - see the section on themes below.

Note that support for some older browser versions - including IE6 and IE7 - has been dropped in Vaadin 7. If you absolutely need them, Vaadin 6 will continue to support them until its planned end of life (June 2014, five years from release of 6.0).

If you have problems with specific topics, see the related sections of the migration guide.

In case you need more help with the migration, the Vaadin team also provides professional services.

Converting an Eclipse project

If you have an existing Vaadin 6 Eclipse project, the easiest way to get up and running with Vaadin 7 is to switch to Ivy for dependency management. In the project properties, select Project Facets and change the Vaadin plug-in version to 7.0. If necessary, upgrade also the Java and Dynamic Web Module facets. Make sure you use the latest version of the Eclipse plug-in from the update site https://vaadin.com/framework/get-started#eclipse for this, and note that currently installing it also requires that the IvyDE update site is configured. We will attempt to eliminate this additional complication soon.

Ivy dependency management can also be configured by hand by adding the files ivy.xml and ivysettings.xml to the root of the project and using them from Eclipse (with the IvyDE plug-in), Ant or other build system. For examples of the two files, see e.g. here and update VAADIN_VERSION in the file ivy.xml.

Note that Vaadin 7 requires Java version 6 or higher and servlet version 2.4 or higher (or portlet 2.0 or higher). If your project is set up for older versions, update the corresponding facets.

Converting a Maven project

Converting a Maven project is usually quite straightforward: replace the Vaadin dependency with dependencies to the needed Vaadin artifacts, remove any dependencies on GWT JARs, replace the GWT plug-in with the Vaadin plug-in and recompile everything. The easiest way to get the required sections and dependencies is to create a new project from the vaadin-application-archetype and copy the relevant sections from it to your project.

Note that Vaadin 7 requires Java version 6 or higher and servlet version 2.4 or higher (or portlet 2.0 or higher). If your project is set up for older versions, update the corresponding dependencies and compiler version.

Content for Windows, Panels and More

In Vaadin 6, Window, Panel and some other components had a default layout and addComponent() etc. As this often caused confusion and caused layout problems when unaware of the implicit layout or forgetting to set its layout parameters, Vaadin 7 now requires explicitly setting the content. See e.g. Creating a basic application

If you want to minimize the impact of this on the look and theme of an old application, you can reproduce the old structure simply by setting a VerticalLayout (with margins enabled) as the content and add your components to it rather than the Panel/UI/Window.

Note that the class Window is now only used for sub-windows, not browser level windows.

Information related to browser windows in now in Page, including browser window size, URI fragment and page title. Setting the browser location (redirecting to a URL) can also be performed via Page.

The API for Notifications has also changed, static methods Notification.show() are now used instead of Window.showNotification().

The current UI, Page, VaadinService, VaadinRequest and VaadinResponse instances are easily accessible using UI.getCurrent(), Page.getCurrent() etc. The session can be obtained using UI.getSession() and the request and response are available from VaadinService.getCurrent(). Thus, no more need for an explicit ThreadLocal to keep track of them.

VaadinSession also provides the new entry point for locking access to Vaadin components from background threads, replacing the old approach of synchronizing to the Application instance - see the javadoc for VaadinSession.lock() for more details.

To customize the creation of UIs - for instance to create different UIs for mobile and desktop devices - a custom UIProvider can be used.

Forms and Data Binding

What enterprise applications are all about is data, and the data entry side in Vaadin 6 has been lacking in customizability. While it has been possible to create arbitrary forms for data input, many situations have required either bypassing the Form mechanism or using complicated tricks to customize their layouts etc.

Although Form is still there in Vaadin 7 and a lot of old code for data binding works mostly as is, version 7 brings something better:

If you want to keep using the old mechanisms, just note that e.g. TextField now has the type String, and automatic conversions are applied as well as validation performed on values converted to the data model type. You can migrate data entry views form by form.

The ancient QueryContainer has been removed, so it is time to switch to SQLContainer or some other container implementation.

If you are using a custom implementation of Container.Indexed, there is one more method to implement - see the javadoc of getItemIds(int, int) for details and a utility making implementing it easy.

Property.toString() should not be used to try to get the value of the property, use Property.getValue() instead.


If your project relies on add-ons from Vaadin Directory, note that not all of them have been updated for Vaadin 7, and a few might only be compatible with older Vaadin 7 beta versions. Check the add-ons you use before committing to migration.

You may need to click "Available for 7" on the add-on page to get the correct add-on version.

You can see a list of add-ons with a version available for Vaadin 7 using the search, although some of them might only be compatible with older alpha and beta versions of Vaadin 7 at the moment.

Note also that a handful of add-ons you might have used are now obsolete as e.g. CustomField is integrated in Vaadin 7.


As long as you use the correct version of the Eclipse or Maven plug-in to compile your widgetset and remove any old GWT libraries from your classpath, not much changes for widgetsets.

The current default widgetset is com.vaadin.DefaultWidgetSet and should be inherited by custom widgetsets, although com.vaadin.terminal.gwt.DefaultWidgetset still exists for backwards compatibility. DefaultWidgetSet is also used on portals, replacing PortalDefaultWidgetSet.

If you are compiling your widgetset e.g. with Ant, there are some changes to the class to execute and its parameters. The class and parameters to use are now "com.google.gwt.dev.Compiler -workDir (working directory) -war (output directory) (widgetset module name)" with optional additional optional parameters before the module name.

If you have optimized your widgetset to limit what components to load initially, see this tutorial and the WidgetSet Optimizer add-on.


The HTML5 DOCTYPE is used by Vaadin 7, which can affect the behavior of some CSS rules.Vaadin 7 brings a new option to create your themes, with SCSS syntax of SASS supporting variables, nested blocks and mix-ins for easier reuse of definitions etc.

To get your old application running without bigger changes, just import e.g. "../reindeer/legacy-styles.css" instead of "../reindeer/styles.css" and take the application for a spin. There will most likely be some changes to be done in your theme, but the main parts should be there.

The themes also support mixing components from multiple themes and using multiple applications with different themes on the same page, which can be especially useful for portlets. However, these depend on fully migrating your themes to the SCSS format with a theme name selector.

To take advantage of the new features, see Creating a theme using Sass and Customizing component theme with Sass.

Note that the SCSS theme needs to be compiled to CSS before use - in development mode, this takes place automatically on the fly whenever the theme is loaded, but when moving to production mode, you need to run the theme compiler on it to produce a pre-compiled static theme.

CSS can be used to style components somewhat more freely than in Vaadin 6.

The DOM structure of several layouts has changed, which might require changes to themes for layouts. See also the section on layouts below.

In addition to low-level support for handling URI fragments Vaadin 7 also provides a higher level navigation framework, allowing you to focus on the content of your views rather than the mechanics of how to navigate to them.

The best way to get acquainted with the new navigation features is to check the tutorials on creating a bookmarkable application, using parameters with views, access control for views and view change confirmations.

When logging out a user, you can use Page.setLocation() to redirect the user to a suitable page.

Extending the Servlet

As ApplicationServlet moved to history and is replaced by VaadinServlet, many customizations you have made to it need a rewrite.

The most common customizations:

Note also that TransactionListener, ServletRequestListener and PortletRequestListener have been removed.

Many things that used to be taken care of by ApplicationServlet are now distributed among VaadinServletService, VaadinSession, VaadinService etc. You can get a VaadinSession with Component.getSession() and VaadinService e.g. with VaadinSession.getService().

System messages that used to be configured by "overriding" a static method Application.getSystemMessages() are now set in VaadinService using a SystemMessagesProvider.

Client side widgets

For add-on authors and creators of custom widgets, the biggest changes in Vaadin 7 have perhaps taken place on the client side and in client-server communication.

The first big change is a separation of the client side UI widgets and the code handling communication with the server (Connector). The familiar VLabel is still the client side widget corresponding to the server side component Label, but the communication part has been split off into LabelConnector. The annotations linking the client side and the server side have also changed, now the LabelConnector has an @Connect annotation linking it to the server side component Label. The book provides some background and the tutorial on creating a simple component shows an example.

The connector communicates with the server primarily via shared state from the server to the client and RPC calls from client to server and from server to client, with a larger set of supported data types. For component containers, the hierarchy of the contained components is sent separately.

The old mechanism with UIDL, paintContent() and changeVariables() is still there for a while to ease migration, but it is recommended to update your components to the new mechanisms, which also tend to result in much cleaner code. Using the old mechanisms requires implementing LegacyComponent.

There are also new features such as support for Extensions (components which extend the UI or other components without having a widget in a layout) and support for JavaScript, also for implementing components and extensions, which might simplify the implementation of some components. Shared state and RPC can also be used from JavaScript, and there are other techniques for client-server communication.

Package names for the client side have changed but a simple import reorganization by the IDE should be able to take care of that, the new packages are under com.vaadin.client.ui.

If you have implemented a component that contains other components (HasComponents, ComponentContainer) or have client side widgets which do size calculations etc, see the layouts chapter - these should now be much simpler to implement than previously, although much of custom layout widgets will probably need to be rewritten.

A final note about client side development: SuperDevMode has been integrated to Vaadin 7, eliminating the need for browser plug-ins in many cases when debugging client side code.

Migration steps (quick and dirty)

  • Create a connector class for the add-on

  • Extend LegacyConnector, override the getWidget() method, change its signature to return VMyWidget and implement it as return (VMyWidget) super.getWidget();

  • Replace the @ClientWidget(VMyWidget.class) annotation (on the server-side component) with @Connect(MyServerSideComponent.class) on the connector class

  • Remove the call to super.updateFromUIDL(…​) in VMyWidget.updateFromUIDL(…​) if no such method exists in the superclass.

  • If the widget has implemented setHeight and setWidth, make the connector implement SimpleManagedLayout and move the layout logic to the layout() method.

  • The actual sizes of the widget is available through getLayoutManager().getOuterHeight(getWidget().getElement()) and similar for the width.

  • If the widget implements ContainerResizedListener, make the connector implement SimpleManagedLayout and call getWidget().iLayout() from the layout() method.

  • Be prepared for problems if you are doing layouting in updateFromUIDL as the actual size of a relatively sized widget will most likely change during the layout phase, i.e. after updateFromUIDL

The connector class should look like

public class MyConnector extends LegacyConnector {
  public VMyWidget getWidget() {
    return (VMyWidget) super.getWidget();
  • Implement the interface LegacyComponent in the server side class

  • If your widget has not delegated caption handling to the framework (i.e. used ApplicationConnection.updateComponent(…​, …​, false) you should override delegateCaptionHandling() in your connector and return false. Please note, however, that this is not recommended for most widgets.

Basic widget add-on using Vaadin 7 APIs

Note: migration to new communication mechanisms etc. should be performed step by step.These instructions continue from where the quick and dirty migration ended.

  • Intermediate step: move updateFromUIDL(…​) implementation from the widget to the connector

  • Change the visibility of any methods and fields it accesses in the widget to "package"

  • Intermediate step: design an API for the widget that does not access Vaadin communication mechanisms directly

  • Use listeners for events from the widget to the server

  • Use setters and action methods for server to client modifications

  • Convert state variables and their transmission in paintContent()/updateFromUIDL() to use shared state

  • Convert one-time actions (events etc.) to use RPC

  • Remove "implements LegacyComponent" from the server-side class and the methods paintContent() and changeVariables()

  • Remove "implements Paintable" or "extends LegacyConnector" and updateFromUIDL() from the client-side connector class (extend AbstractComponentConnector instead of LegacyConnector)

Layouts and Component Containers

While the server side API of various layouts has not changed much, the implementations on the client side have. With the currently supported browsers, much more can now be calculated by the browser, so Vaadin layouts often do not need to measure and calculate sizes.

Most of the differences are only relevant to those who develop client side component containers, but a few can also affect other developers.

Among the changes affecting others than layout developers, CssLayout now consists of a single DIV instead of three nested elements, and CSS can be used to do more customization than in previous Vaadin versions. Also other layouts have changed in terms of their DOM structure on the client, which might require changes to themes. The interface MarginHandler is now only implemented by layouts that actually support it, not in AbstractLayout, and margins should be set in CSS for CssLayout.

When implementing components that are not full-blown layouts (with addComponent(), removeComponent() etc.) but should contain other components, the simpler interface HasComponents should be used instead of ComponentContainer.

For those implementing new component containers or layouts, see the related tutorials Creating a simple component container and Widget styling using only CSS.

Migration steps for ComponentContainers

These continue from where the add-on migration steps above left off

  • Component containers (e.g. layouts) require more changes as the underlying layout mechanisms and updates have changed

  • Client-side child connectors are now created by the framework

  • Hierarchy change events. Guaranteed to run before child calls updateCaption. Create any child slots here and attach the widget.

  • Don’t paint children

  • Don’t call child.updateFromUidl

  • Update caption management (called before updateFromUidl, from state change event listener)

Miscellaneous Changes

Many overloaded addListener() methods have been deprecated. Use addClickListener(), addValueChangeListener() etc. instead of them, reducing ambiguity and the need for explicit casts.

Many constants have been replaced with enums, although in most cases the old names refer to enum values to ease migration.

If using background threads, locking has changed: there is no longer an Application class to synchronize to, but getSession().lock() etc. should be used - see the javadoc for details on its correct use, using a correct try-finally is crucial for building reliable multi-threaded Vaadin applications.

ApplicationResource has been replaced with ConnectorResource, taking different parameters.

URIHandler has been replaced with RequestHandler. See also the related class DownloadStream.

JavaScript can now be executed using JavaScript.execute().

Various methods that were deprecated until 6.8 etc. have been removed, and some classes and methods have been deprecated. In most of those cases, the deprecation comment or javadoc indicates what to use as a replacement.

AbstractComponent.isEnabled() and isVisible() do not take the state of the parent component into account, but only inquire the state set for the component itself. A component inside a disabled component still is disabled, and one inside an invisible component is not rendered on the browser.

No information is sent to the browser about components marked as invisible - they simply do not exist from the point of view of the client.


Button is no longer a Field and does not have a constructor that takes a method name to call, use anonymous inner class instead. Because of this, CheckBox is no longer a Button and uses a ValueChangeListener instead of a ClickListener.

DateField no longer supports milliseconds and its default resolution is day.

Label now supports converters.

RichTextArea custom formatting methods removed, use a PropertyFormatter or a Converter instead of overriding formatting methods.

Need help?

If you need any advice, training or hands on help in migrating your app to Vaadin 7, please be in touch with sales@vaadin.com. Vaadin team would be happy to be at your service.