Rewrite: form submit action

[kevindeyne]

Will need a custom Thymeleaf tag that triggers on a form submit.

• Actual form submits have to be cancelled
• The form must become available as parameter to the controller method as a Map<String, Object> or map onto a POJO.
• (Optional) A common pattern is to disable a button after button press until the message is resolved, to prevent double-clicking to fire an event twice. Perhaps this should be an option with this default on?
• (Optional) Validation of forms is a very common pattern. Is there a way we can make this easier in Medusa?

[kevindeyne]

Implemented the basics of form tag: https://medusa-showcase.herokuapp.com/detail/form-submit
Would still need to think about validation/button disabling

[kevindeyne]

For Validation, consider integration with https://github.com/making/yavi which seems to have traction on github.

Validation should likely work on both JS side and backend. The validation messages should be able to deal with internationalization/maybe just different strings.

[dirkdeyne]

One thing I noticed: when adding Session in the submit method, it needs to be the last argument of that method.
Note: for other calls like m:click the position of the session argument can be first or last...

ref: #304

[dirkdeyne]

Failed to use multi-select in form ref: sample in medusa-ui path: '/multi-select'

[dirkdeyne]

Failed to use multi-select in form ref: sample in medusa-ui path: '/multi-select'

Issue above is fixed. 👍

But handling multi-select in the controller is still cumbersome:

• null when not present
• Object when a single option selected
• Object[] when multiple options selected

public List<Attribute> options( Map<String, Object> form) {
  ...
 // handle multi-select
 // value is null when not present
 if (null != form && form.containsKey("options")) {
     Object options= form.get("selected");
     if (options instanceof String) {
         // handle single select
      } else {
         for (Object option: (Object[]) options) {
            // handle multiple selections
            ... option.toString();
         }
      }
   }
  ....
}

[kevindeyne]

Any easier now? I've made it resolve to a dynamic List instead of an Object[] now.

So you should be able to do something like:
Map<String, List<String>> form if you only expect multi lists to show up in the form.

I'm not really sure how I could make a map that does both single values and multi values easier otherwise. That's kind of what the POJO mapping is for.

[dirkdeyne]

The problem is not Object versus String, but Object versus Object[] (or String versus String[])

The multi-select has no problems when multiple options are selected, but occurs when only a single option is selected.
One would expect an Array with one Object, but instead, the selected option is an Object.

When using a map, you can use the workaround like in the above example.
When using a POJO there is no workaround, you get an error:

MismatchedInputException: Cannot construct instance of java.util.ArrayList (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value

Ref: multi-select in medusa-ui Sample application

[kevindeyne]

Applied JS fix as discussed, maybe this will solve the problem?

[dirkdeyne]

Select multiple works fine now! 👍
Included detection for input fields with an identical name #326
These too must send data as an Array.

[dirkdeyne]

For now only look at checkboxes with identical names