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https://issues.apache.org/jira/browse/SLING-2803?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13618142#comment-13618142
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Eric Norman edited comment on SLING-2803 at 3/30/13 7:56 PM:
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If I recall correctly, sometimes errors occur before the post processor gets a
chance to run. So I would think doing validation as a pre processor would
catch a larger universe of errors and give the developer a better chance of
providing a meaningful error back to the user. If you are doing validation in
a post processor, there could have been other exceptions raised before it gets
to that point. However, doing a generic validation technique could be complex
to do right since the request parameters can be expressed in many different
ways.
In the sling projects where I have done validation, I have always registered my
own servlet/script for the POST method that pre-validates the expected request
parameters. If there are any errors, I collect the info and forward back to
the original html page to display the form again with the errors reported. If
there are no validation errors, I would just forward the request to the default
sling post servlet to do the rest of the work.
Trying to do validation for the generic post servlet is a more challenging
problem since I can imagine situations where a submitted value is valid for a
node/resource type but not valid for a specific use case. For example, perhaps
in a field in a form is sending a date value that the user picks from a
calendar. The validator for the resource type could validate that the supplied
value has the right syntax for a calendar value, but perhaps in some usage of
that resource type, the calendar value must be in future. My point is that I
wouldn't want to have to make new resource types to modify the validation
behavior for different contexts.
was (Author: edn):
If I recall correctly, sometimes errors occur before the post processor
gets a chance to run. So I would think doing validation as a pre processor
would catch a larger universe of errors and give the developer a better chance
of providing a meaningful error back to the user. If you are doing validation
in a post processor, there could have been other exceptions raised before it
gets to that point. However, doing a generic validation technique could be
complex to do right since the request parameters can be expressed in many
different ways.
In the sling projects where I have done validation, I have always registered my
own servlet/script for the POST method that pre-validates the expected request
parameters. If there are any errors, I collect the info and forward back to
the original html page to display the form again with the errors reported. If
there are no validation errors, I would just forward the request to the default
sling post servlet to do the rest of the work.
Trying to do validation for the generic post servlet is a more challenging
problem since I can imagine situations where a submitted value is valid for a
node/resource type but not valid for a specific use case. For example, perhaps
in a field in a form is sending a date value that the user picks from a
calendar. The validator resource type could validate that the supplied value
has the right syntax for a calendar value, but perhaps in some usage of that
resource type, the calendar value must be in future. My point is that I
wouldn't want to have to make new resource types to modify the validation
behavior for different contexts.
> Create a Validation module capable of validating POST requests or Resources
> ---------------------------------------------------------------------------
>
> Key: SLING-2803
> URL: https://issues.apache.org/jira/browse/SLING-2803
> Project: Sling
> Issue Type: New Feature
> Reporter: Radu Cotescu
>
> Several Sling users have asked in the past [1] about a Validation mechanism
> in Sling that's able to validate data coming from the user. However, such a
> module is still missing.
> This issue is meant to track the work progress on such a module.
> Ideally the module should be able to validate both request parameters and
> Resources, by obtaining their properties via a ValueMap and provide feedback
> in case of a validation error.
> [1] - http://sling.markmail.org/search/?q=validation
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