Form Extension

[hurelhuyag]

I used to dream about auto-generating jakarta validation annotations into HTML input attributes. This way, both front-end and back-end could have same validation. Since JTE has extensions, I'm wondering if this is possible.

For example lets declare model like this:

import jakarta.validation.constraints.NotEmpty;
record DemoForm(@NotEmpty String firstname, @NotEmpty String lastname) {}

And write jte template something like this:

@param DemoForm form
@form(form)
  @form.input("firstname")
  @form.input("lastname")
  <button>Submit</button>
@endform

Then compile time generates output:

<form>
  <input name="firstname" value="${form.firstname()}" required="true" />
  <input name="lastname" value="${form.lastname()}" required="true" />
  <button>Submit</button>
</form>

required="true" is generated because of @NotEmpty annotation.

Is this possible with JTE extensions?

[edward3h]

JTE extensions run after the template engine has generated the code that renders a template. They can generate additional files but won't modify the template parsing. So I don't think they would help for this.

The suggested functionality is beyond the scope of what JTE is intended to do by itself.

You can use template calls for simple components.

If was to implement something like this, I might create a "metadata" type derived from the record. The API would be something like:

interface FormData {
  String action(); // etc. for top-level form attributes
  List<FormField> fields();
}

interface FormField {
  String name();
  Object value();
  boolean required(); 
}

The implementation might be generated by an annotation processor, or use reflection.

The template would be like:

@param FormData form

<form action=${form.action()}>
  @for(var field : form.fields())
    <input name="${field.name()}" value="${field.value()}" required="${field.required()}" />
  @endfor
</form>

Unless you need a lot of this kind of thing, I would just write the HTML though.