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Creating Vaadin Portlets

Describes how to build your own Vaadin Portlets and run them.

In this chapter, you learn how to create Vaadin Portlets and how to deploy these portlets to the Liferay 7 Digital Experience Platform.

Creating a Vaadin Portlet

You have two ways to start the creation of a Vaadin Portlet: starting from the beginning or from base-starter-flow-portlet project. The starter project contains everything needed to quickly create your own Vaadin Portlet, with the code laid out in advance.

To become familiar with setting up a Vaadin Portlet project manually, you start with a simple Vaadin project and then convert it into a Vaadin Portlet project.

Setting Up Portlet Project

First, download the Vaadin base starter

Next, update your pom.xml:

  1. Add the following dependencies:

  2. Add a build-frontend goal to vaadin-maven-plugin, as Vaadin Portlet doesn’t work in development mode running vaadin-dev-server.

Creating the Portlet

In the most basic setup, Vaadin Portlets consist of two classes:

  • A portlet class, which extends VaadinLiferayPortlet or VaadinPortlet (when running in non-Liferay Portal)

The portlet class acts as the entry point for your Vaadin Portlet application. It serves a similar function to a Servlet, but in a portlet context.

  • A portlet view class, which extends Component

The view class, which can be any normal Vaadin component, contains the contents of your Vaadin Portlet. You could use an existing component through extension, composition, or as is. Or create an entirely new component for your Vaadin Portlet. VaadinPortlet and VaadinLiferayPortlet are generic classes and take the selected view class as a type parameter.

Preparing the Classes

Find the provided with the project and create in the same folder. Inside the file, add the following code: for Liferay Portals

    portletName = "MyLiferayPortlet",
    dependencies = @Dependency(name = "PortletHub", scope = "javax.portlet", version = "3.0.0")
public class MyLiferayPortlet extends VaadinLiferayPortlet<MainView> {

} for non-Liferay Portals

public class MyPortlet extends VaadinPortlet<MainView> {


Next, open the Remove both the @Route and @PWA annotations, which don’t make sense for your portlet.

The final code should look something like this:

public class MainView extends VerticalLayout {

    public MainView() {
        Button button = new Button("Click me",
                event ->"Clicked!"));

When a user clicks on the button, a notification with the text "Clicked!" should appear in the lower-left corner of the browser window. Your Vaadin Portlet is almost ready to go; you only need to make it ready for deployment.

Setting Portlet Deployment Descriptor

In the Portlet 3.0 specification, the portlet deployment descriptor can be configured in two ways:

  • portlet.xml (backwards-compatible)

  • annotations (only 3.0)

You use the portlet.xml to configure your portlet deployment. The portlet.xml serves the same purpose as web.xml does for servlets.

Create portlet.xml under {project directory}/src/main/webapp/WEB-INF and add the following contents:

<?xml version="1.0"?>
<portlet-app xmlns=""
            <title>My Test Portlet - MyPortlet</title>
            <short-title>My Test Portlet</short-title>

The <portlet-class> points to your class extending VaadinPortlet/VaadinLiferayPortlet with a fully qualified name. The <supports> section contains the portlet modes (<portlet-mode> tag) the portlet supports. You can learn more about portlet modes for Vaadin Portlet in the next chapter

Setting Portlet Descriptors Specific to Liferay

To run Vaadin Portlets in Liferay Portal, the following descriptors are also needed:

  • liferay-display.xml - describes the category the portlet appears under in the Add menu of Liferay’s Widgets bar.

  • liferay-portlet.xml - describes Liferay-specific enhancements for Java Specification Requests (JSR) 286 portlets installed on a Liferay Portal server.

Create liferay-display.xml and liferay-portlet.xml under {project directory}/src/main/webapp/WEB-INF and add the following contents:

<?xml version="1.0"?>
<!DOCTYPE display PUBLIC "-//Liferay//DTD Display 6.2.0//EN" "">

    <category name="Vaadin Liferay Portlets">
        <portlet id="MyLiferayPortlet" />
<?xml version="1.0"?>
<!DOCTYPE liferay-portlet-app PUBLIC "-//Liferay//DTD Portlet Application 7.1.0//EN" "">

        <!-- Instanceable parameter means whether we can add the Portlet more than once on same page.-->
The parameter instanceable specifies whether the Portlet can be added more than once on same page. If it’s false, it can be added only once on a page.

Setting External Stats URL in Liferay

If your portlet runs in Liferay Portal, add the following resource file flow-build-info.json into {project directory}/src/main/resources/META-INF/VAADIN/config with the contents:

    "externalStatsUrl": "/o/vaadin-portlet-static/VAADIN/config/stats.json"

Enable webpack for Front-End Builds

Starting with Vaadin 23.2, Vite is the default tool for front-end builds. However, Vaadin Portlet requires webpack to be used. To use webpack, you must enable it with the webpackForFrontendBuild feature flag.


See Feature Flags for more information.

Deploying Your Vaadin Portlet

Building Vaadin Portlet

To build the portlet you created, you must add some more configuration to the pom.xml. Vaadin Portlet deployments are packaged into two WAR files. One WAR file contains all the static resources shared by the Vaadin Portlets, and the other WAR file contains the actual portlets. This allows for more complex scenarios where multiple portlets come from separate WAR files; see Creating Multi-Module Portlet Project.

Add the following plugin configuration to the pom.xml:

    <!-- Generate 2 war archives for portlet. One for the portlet(s) and another for the static files -->
        <!-- Generate a static war 'vaadin-portlet-static.war' with all static files -->
                <!-- static files should contain flow-client and all build files generated in VAADIN/ -->

                        <!-- this is relative to the pom.xml directory -->
                        <!-- Include all files and folders below <directory> -->
                        <!-- this is relative to the pom.xml directory -->
                            Include all config files to root except flow-build-info
                            that is not needed at runtime when running fronted builds
                        <!-- do not include  file as it contains portlet configuration -->
        <!-- Generate the portlet war excluding any static build files -->
                        Include original flow-build-info.json, not the one produced by vaadin plugin
                        and included in the static portlet

Here you build two WAR files: one for the application (all portlets in this project), and one for the static files needed by the portlets (which contains the front-end bundle and client engine).

The static WAR is built as a portal window that can load only a single Vaadin bundle and client engine at a time. This provides a simple way for all the portlets on the page to use the same static bundle.

Configuring Static Resources

If you need to change the name of the static assets WAR (by default, vaadin-portlet-static), you can do this via the vaadin.portlet.static.resources.mapping application property. For example, if you want to serve static resources from vaadin-static-resources.war, you need to

  • rename the static WAR to vaadin-static-resources in the pom.xml;

  • change the static portlet name in flow-build-info.json (if Liferay is used);

  • pass the value /vaadin-static-resources/ (for Liferay Portal, it would be /o/vaadin-portlet-resources/) via the application property to the Vaadin application; that is, on the Tomcat web server you would:

    • on *nix-based operating systems, create or edit the file $CATALINA_BASE/bin/ with the line
      JAVA_OPTS="$JAVA_OPTS -Dvaadin.portlet.static.resources.mapping=/vaadin-static-resources/";

    • on Windows operating systems, create or edit the file %CATALINA_BASE%\bin\setenv.bat with the line
      set "JAVA_OPTS=%JAVA_OPTS% -Dvaadin.portlet.static.resources.mapping=/vaadin-static-resources/".

Deploying Vaadin Portlet to Liferay 7

  1. Run mvn install in your project directory.

  2. Download Liferay Bundle and extract it to a location you prefer.

  3. Add the following parameter to Liferay Tomcat’s ({liferay home}/tomcat-<version>/bin): -Dvaadin.portlet.static.resources.mapping=/o/vaadin-portlet-static/

  4. Download and copy the JNA dependency JARs of the specific version into {liferay home}/tomcat-<version>/webapps/ROOT/WEB-INF/lib (or shielded-container-lib depending on the version):, This is needed because Vaadin Portlet uses a newer version of the Java Native Access (JNA) library which can cause conflicts with the version that Liferay uses.

  5. Create a file in Liferay’s home directory and place the following property there:

  6. Copy both WAR files from {project directory}/target into {liferay home}/deploy.

  7. Start the web server by

    • opening a command prompt in the {bundle extract directory} folder;

    • running the command ./{tomcat-version}/bin/ or ./{tomcat-version}/bin/startup.bat (Unix/Windows).

  8. Once the web server has started, navigate to http://localhost:8080/

  9. Follow the instructions of the Liferay wizard to set up a new user and sign in to the Portal.

  10. Click on the "Menu" button at the top-left corner to open the menu console.

  11. Find and click on the "Page tree" link and click on the "+" button to add a new page.

  12. Select "Widget Page", give it a name and select the appropriate layout.

  13. In the "Look and Feel" tab, select "Define a specific look and feel for this page" and enable "Show Maximize/Minimize".

  14. Click "Save" and navigate to the home page, then to the layout you created.

  15. Click the "Add" button, which is usually placed at the top-right corner, find the category "Vaadin Liferay Portlets", open it and drag the portlet item from the panel to the page.

  16. You should see the portlet with the title MY TEST PORTLET - MYPORTLET and a Click me button in the content area.