Client-Side Validation with MyFaces ExtVal & BV

!!! DRAFT !!!

Required features

• Adding js transparently based on
  • Constraints
  • JSF validators/validation methods
  • JSF converters (client-side conversion (ClientConverter))
• Client side conversion(ClientConverter) is also required to be compatible with server side validation processing.
• Group validation (partial validation)
• Skipable validation (see @SkipValidation)
  • Skip validation for immediate components
• Bypass validation for command components
  (see @BypassValidation and @BypassBeanValidation (= existing ExtVal-add-ons))
• Cross-validation
• Validation triggered by
  • Input components
    • Connecting validation to events (onblur, ...)
  • Command components
• Client interception of validation exceptions
  (e.g. for generic component highlighting,...)
• Interaction with Ajax-validation
  (e.g. for model aware validation)
• Restrict exposing sensitive information to the client -> fallback to Ajax validation
• Input masking for dates, numbers, etc., based on the server side formats.
• Correctly positioning and styling error messages, so the user doesn't see the difference between client-side and server-side generated messages.
  (we might need to do some tricks here, since UIMessage(s) doesn't render anything when there are no messages).
  

Reusing annotations

• Any validation constraints
• @ResourceDependency (@ResourceDependencies)
• Reuse existing BeanValidation annotations
  (we probably need to disable Bean Validation, because otherwise the user may see double error messages)
  

Changing existing annotations

• Additional target for @ResourceDependency (java.lang.annotation.ElementType.METHOD)
  (for validation methods)

Possible approaches to mark client-side validation

• Implicit via @ResourceDependency
• Additional interface
• @ClientValidator
  

Use a pluggable marker mechanism. -> Impl. for JSF 1.x are able to provide an equivalent to @ResourceDependency

At the client

• JavaScript
• CSS (for highlighting - has to consider possible skinning approaches)
• Minimize JS code in web page (performance, external JS file may be cached, readability...)
  

At the server

• JSF
• MyFaces ExtVal
  • Core
  • JSR 303 validation module
  • Client-side validation add-on
    

(It should also work with JSF 1.x! JSF 2.1+ might specify all/some of the final concepts.)

Possibilities for hosting add-on(s)

• ExtVal add-on
  • http://code.google.com/p/primefaces/
  • http://code.google.com/p/os890
  • http://code.google.com/p/sandbox890
    

Existing (generic) solutions which might be part of the final approach

• Trinidad client-side validation (concept of org.apache.myfaces.trinidad.validator.ClientValidator)
  

Concepts to think about

• Client-side facade for triggering validation
  (behind the facade there is a "storage/repository" of validators and one for validation rules
  (concerning events, conditions for skipping validation, maybe validation messages, target of validation messages)
  such repositories have to be aware of PPR)
  Usage within the page would be something like: javax.faces.Page.getInstance().validate(this, ...)
  If "this" is an input field, the field is validated based on the information in the repositories.
  If "this" is form, the whole form is validated based on the information in the repositories.