Breaking changes in Vaadin Flow 25

[mshabarov]

Deprecated API

• Remove deprecated API in Vaadin 25.0 flow#21396

New Theming system

• Styles declared via @CssImport should be isolated within exported component flow#21272
• Load Aura theme by default in greenfield projects flow#21609
• Shadow DOM injection through components folder behind feature flag in V25 flow#21608 ⏳
• WebComponentExporter should copy @font-face declarations to document body in V25 flow#21607
• Don’t load Lumo by default in V25 flow#21606 ⏳
• Lumo should just load stylesheets in V25 flow#21605 ⏳

Frontend

• chore: Use React 19 flow#21523 ⏳

Polymer -> Lit

• Ensure Flow works without Polymer in v25 flow#21421

Binder

• Adds isApplied feature for Binding flow#18540
• Binder.validate() no longer fails with "bean level validators have been configured but no bean is currently set" when in buffered mode flow#18121 / Binder.validate() fails with "bean level validators have been configured but no bean is currently set" when in buffered mode flow#18120
• https://vaadin.slack.com/archives/C6RAXJATF/p1729494025391779

Dependencies

• chore(deps): bump org.hibernate.validator:hibernate-validator from 8.0.2.Final to 9.0.0.Final flow#21466 ⏳
• Remove "construct-style-sheets-polyfill" in Vaadin 25 flow#21675

Other

• Deprecate VaadinWebSecurity in Vaadin 24 and remove in Vaadin 25 flow#21410 ⏳
• DeploymentConfiguration is retained in VaadinSession over session store-load cycle flow#18318
• Restrict VaadinWebSecurity to urlMapping flow#17624 ⏳
• Deny access if Flow layout class has no annotation flow#21832
• Provide method to set Anchor's router-ignore flag. flow#17617 (comment) / feature: provide an API to make router ignore an anchor flow#17745 (comment)
• Set closeIdleSessions = true by default in Vaadin 25 flow#18153 (WebSocket connection vs http connection, push, let's ask on the forum what is an appropriate default in projects)