3.1.0.alpha2 - Prerelease for Vaadin 16

Vaadin Flow 3.1.0.alpha2 is a prerelease of the Java Framework targeted to Vaadin 16. To try it out, use the latest 16 prerelease available from the Vaadin prereleases Maven repository.

Changes since 3.1.0.alpha1
For all changes, see changes since 3.0

3.1 Feature Highlights

Automatic Node installation

• Available from Vaadin versions 14.2 and 16
• If no global or local Node installation is found Node will be automatically installed to ~/.vaadin
  • Only requires the first project to install as later can use the same installation
  • No need to have Node installed for CI
• Uses proxy data from
  • System properties
  • {project}/.npmrc
  • ~/.npmrc
  • Environment variables

pnpm is the default frontend package manager

• Now pnpm is used by default instead of npm
  • npm was still default in Vaadin 14.2 and 15
• No migration needed - pnpm is installed once to /.vaadin inside home folder. See differences here for more information about what has changed

Devmode is run as a separate thread to speed up server startup

• Allows server to continue startup parallel to Flow development mode process which runs pnpm/npm and webpack build
• The browser shows a white page that is automatically refreshed to open app once devmode process has finished
• As server is started up faster, there is no timeout from "run from IDE" or from server plugins

Minor improvements in 3.1

• API in UI for switching between direction RTL / LTR (document.dir)
• Flow 3.1 contains all improvements shipped in Flow 2.2.0.beta1, see release notes for detailed list.

Known Issues and Limitations in 3.1

• pnpm is not able to resolve dependencies to git commits with the "short" hash format. See details and workaround from #7406.

Deprecations since 3.0

None.