handle a String[] via the PortletPreferences (Liferay6.2) - html

Question

I have built a MVCPortlet that runs on Liferay 6.2.
It uses a PortletPReferences page that works fine to set/get String preferences parameters via the top right configuration menu.
Now I would need to store there a String[] instead of a regular String.
It seems to be possible as you can store and get some String[] via
portletPreferences.getValues("paramName", StringArrayData);
I want the data to be stored from a form multiline select.
I suppose that I need to call my derived controller (derived from DefaultConfigurationAction) and invoke there portletPreferences.setValues(String, String[]);
If so, in the middle, I will neeed the config jsp to pass the String[] array to the controller via a
request.setAttribute(String, String[]);
Do you think the app can work this way in theory?
If so, here are the problems I encountered when trying to make it work:
For any reason, in my config jsp,
request.setAttribute("paramName", myStringArray);
does not work ->
actionRequest.getAttribute("paramName")
retrieves null in my controller
This is quite a surprise as this usually works.
Maybe the config.jsp works a bit differently than standard jsps?
Then, how can I turn my multiline html select into a String[] attribute?
I had in mind to call a JS function when the form is submitted.
this JS function would generate the StringArray from the select ID (easy)
and then would call the actionURL (more complicated).
Is it possible?
thx in advance.

Answer 1

In your render phase (e.g. in config.jsp) you can't change the state of your portlet - e.g. I wouldn't expect any attributes to persist that are set there. They might survive to the end of the render phase, but not persist to the next action call. From a rendered UI to action they need to be part of a form, not request attributes.
You can store portletpreferences as String[], no problem, see the API for getting and setting them

Answer 2

I think maybe you can use an array in client side, and you can update the javascript array, when user is selecting new values.
So you have the javascript array, then when user click on the action, you can execute the action from javascript also, something like this:
Here "products" is the array with your products.
A.io.request(url, {type: 'POST',
data: {
key: products
},
on: {
success: function(event, id, obj) {
}
}
});
From Action methd you can try to get the parameter with:
ParamUtil.getParameterValues(request,"key");