Entity validation API

The Entity validation API consists of Constraint plugins, and their associated Validators, and a mechanism for attaching constraints to the fields of an entity.

Entity Validation API overview

In Drupal 8 Entity validation is moved to a separate Entity validation API and decoupled from form validation.

Defining Constraints (Validations) on Entities and/or Fields.

Constraints ensure data validity, integrity, and enforce business rules. They validate user input and display error messages.

Supported validation constraints [TBD]

List supported validation constraints and their settings.Also, document type-specific default constraints added in automatically here.