Validator Javascript Extension

Introduction

I've written this extension for Commons Validator which dynamically renders the javascript for Form validation. I believe it has significant improvements over the Struts validation javascript rendering (see Features below) as well as abstracting out the rendering into an environment agnostic tool.

The best way to look at this is download and deploy the webapp - it lets you try it out and browse through the source code and generated javascript (runs on Servlet 2.2 or above). Also the java and javascript source code is included in the download.

I've now added a list of issues here and version/changes info here.

Download

validatorjs-1.0.8.zip or validatorjs-1.0.8.tar.gz

These downloads are distributed under the Apache 2.0 License.

Javascript Extension

The main components are the following:

1. ScriptRenderer

Renders the appropriate javascript for a Form's validation to a StringBuffer. This class is most of this proposal. Its agnostic about its environment (e.g. doesn't know anything about Servlets, jsp or Struts) and can be easily plugged into any environment. Its an abstract class that just needs two methods implemented - mainly the getMessage() method to convert message keys into actual messages. In the download there is a new version of the Struts JavascriptValidatorTag which uses a Struts implementation of the ScriptRenderer.

2. FunctionRenderer.java

A FunctionRenderer understands how to render a call to a Validator's javascript validation method. Each Validator will need an associated FunctionRenderer, however having said that there is a GenericFunctionRenderer which can be used for all but one of the existing javascript validations - the only custom FunctionRenderer needed for the existing javascript validators was for the Date Validator.

3. Javascript Validators

I have modified the existing javascript validators. In summary they are smaller, simpler and have more appropriate method signatures. A summary of the difference to the existing ones are...

More appropriate method signatures e.g. validateRequired(field)
Validation methods no longer process an Array of fields - they just validate a single field.
Validation methods no longer call back to get the parameters
Validation methods no longer handle setting field focus or displaying error messages - they only do validation, returning true or false.

As well as the general re-factoring of the methods mentioned above, I have also re-written the Date Validation javascript.

Benefits

I think this is worth doing based on the addtional features alone, but for it would also be good to expand the use of Commons Validator.

Features

Improved Javascript Validators - smaller, simpler and have more appropriate method signatures.
Provides Indexed Field Validation - including ability to provide meaningful indexed error messages.
Enhanced Message Handling - supports bundles, but the main improvement is the ability to include values from the form in the error messages.
Enables Field Level Validation - I have included examples of customized Struts tags which automatically generate field validation in their onchange event.
Improved Date Validation
Better Validation Order - Forms are validated in the order fields are defined in the validation.xml (rather than in Validator order, currently generated by Struts).
Abstracted Renderer - independant of its environment and easily customized.
Configurable Options

Error Limit - limit the number of errors shown to a defined maximum.
Ignore Indexed - don't validate indexed fields.
Stop on the First Error - show one error at a time
Stop On Indexed Error - validate one indexed bean at a time.

Expand Commons Javascript Validator Usage

I believe that this enhacement will firstly open up Commons Javascript Validations to additional developers/software and secondly opens it up to be used in different ways.

Additional Developers/Software

I believe that outside of Struts, the current Commons Validator Javascript implementations are un-useable. This feature would open up Commons Validator to be used in any number of areas. I have no knowledge of them, but what springs to mind are other web frameworks and (possibly) Java Server Faces implementations. Additionally, it would also open it up to other View Presentation technologies - such as Velocity.

Additional Uses

I have created example implementations of the existing Struts html input tags that automatically generate validation javascript for the onchange event and example use of these tags is shown in the download webapp.

Another area of opportunity is in the how errors are handled - the existing Javascript validators simply set the focus on the first field in error and use a Javascript alert() to display the messages. This implementation does the same. However in this implementation the error handling has been put into separate methods that are included in the static ValidatorUtilities.js script (see the processError() and handleFieldError()/handleFormErrors() methods) - these could be easily customized and replaced with more impressive features.

Resolved Issues

This new version I believe will resolve the following issues...

Form Names - Path based validation in Struts requires a '/' in order to work and it only works for either Form Name or Path based validation. In order to get unique function names the patch implemented introduced this restriction. With this extension the issue of function names and the restriction goes away.

Bug 31534 - validateRequired.js uses unsupported DOM method for validation.
Bug 31790 - The JavaScript function validateDate() does not distinguish between datePattern and datePatternStrict

This new version may (I only did a quick scan) help resolving the following issues...

Bug 31509 - html:javascript tag doesn't work right with jsFunctionName set
Bug 29885 - Action based client side validation
Bug 14471 - validator-rules.xml JavaScript fails when field not present in jsp