Using a list of checkboxes

In this recipe, you'll learn how to display a list of checkboxes and when the form is submitted, how to retrieve the selected values in a controller method.

How to do it…

1. In the controller, add a @ModelAttribute method returning a Map object:

   @ModelAttribute("languages")
   public Map<String, String>languages() {
     Map<String, String> m = new HashMap<String, String>();
     m.put("en", "English");
     m.put("fr", "French");
     m.put("de", "German");
     m.put("it", "Italian");
     return m;
   }

2. If a default value is necessary, use a String[] attribute of the default object (refer to the Setting a form's default values using a model object recipe) initialized with some of the Map keys:

   String[] defaultLanguages = {"en", "fr"};
   user.setLanguages(defaultLanguages);

3. In the JSP, use a form:checkboxes element initialized with the @ModelAttribute Map:

   <form:checkboxes items="${languages}" path="languages" />

In the controller that processes the form submission, make...