I have this problem, in a form I have a list of customers that could be more than 300 and, for me, it isn't very simple find over there because I should scroll all results for find a single row!
On the old technology I had a button that opened a pop up where I should research which customer I should select and than I used a javascript for recording the selection on the first form, but It could be a good solution with new technology!
How can I resolve this doubt? What is the best solution for big <select> tag?
You basically want an autocomplete dropdown list. This does not exist in the standard JSF component set and it is also not exactly trivial to implement with JavaScript/jQuery on top of the standard JSF component set because the available values have to be present in the server side's state. You also basically want a dropdown list which is represented by a <div><input><ul><li> instead of a <select><option> because a normal <select> doesn't allow the enduser to type text in. The standard JSF component set does not have a component which renders the desired HTML markup. You'd basically need to create a custom JSF component.
There are 3rd party JSF component libraries which already offer a fullworthy JSF autocomplete dropdown list. It would be easier to use either of them instead of reinventing the wheel by a custom JSF component. Take your pick: