Okay, so to restate and reignite this discussion, let me seed the topic.<br><br>Several members of the EG and many other community members have voiced their concern that the validation mechanism in JSF is insufficient, particularly in regard to inter-component validation, and needs to be rethought/redesigned in a future release. I am deciphering two concerns.<br>
<br>1) Validation is happening in two places, once before model update and once after, which confuses the user (they have to submit the form twice to get all the validation errors)<br>2) Inter-component validation is very complex and in some cases, not possible without a lot of code stealing from the implementation<br>
<br>There are two root causes that have been identified:<br><br>1) The assumption that validation should happen before model update, thus making it possible to only partially use Bean Validator (and the like)<br>2) The coupling of conversion and validation in the life cycle (each component is converted then validated in turn)<br>
<br>The second root cause is easier to solve than the first. Norbert and I (perhaps others as well) believe everything would get a whole lot simpler to start with if conversion was completed before validation began so that when inter-component validation is attempted, all values are in their converted state.<br>
<br>The first root cause is much more challenging because if a value cannot be converted, and you continue into validation, you run the risk of undefined behavior. I suppose you could say that a value which could not be converted results in a null value being assigned with a FacesMessage registered. But are two attempts to submit the form that result in different validation messages really a bad thing. If you enter a bogus number in a number field, the form will yell at you that it cannot proceed without a number. When you enter a number, it may then turn out to be out of range, and that to me is a logical progression.<br>
<br>So the floor is open to discuss a general model for handling validation Please cite use cases and case studies if necessary. We simply cannot let another JSF revision go by without there being a general agreement that validation is sufficient for the development of web applications.<br>
<br>-Dan<br clear="all"><br>-- <br>Dan Allen<br>Senior Software Engineer, Red Hat | Author of Seam in Action<br>Registered Linux User #231597<br><br><a href="http://mojavelinux.com">http://mojavelinux.com</a><br><a href="http://mojavelinux.com/seaminaction">http://mojavelinux.com/seaminaction</a><br>
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