witch use for example a bussiness delegate
And who calls the business delegate? The idea is to deparate presentation, business and data tiers in which any request first comes to the presentation tier components (action or whatever you have), which "knows" which business tier component to invoke and how to perform the search.
In your example, I think when you click the search button, the search criteria should come to the action, which will populate the VO or DTO or whatever business tier data container class you have and then send the VO (containing the search criteria) to the business tier.
Even if you don't do much in the presentaion actions, your front controller should always invoke one type of classes (e.g. actions) as opposed to actions in some cases and delegates in others.