[FIXED] Passing Map<String, Set<String>> from Servlet to JSP Select

Issue

I have a map<String, Set<String>>. I trying to pass the values for this object from servlet to jsp.

Map<String, Set<String>> filter_info= new HashMap<String, Set<String>>();
for(String key: results.keySet())
{
    filter_info.put(key.trim(), new HashSet<String>(Arrays.asList(results.get(key).split(","))));

}
request.setAttribute("filter",filter_info);
this.getServletContext().getRequestDispatcher("/Search.jsp")
                .forward(request, response);

I have two select inputs in my jsp. I am trying to make the options (values of Set<String>) of the second select to change depending on the option (key) selected in the first select.

<form role="search" class="search-form" id="search-form" action="#" method="post">

     <label for="Keys">Keys: </label>
       <select id="Keys">
            <c:forEach var="filter" items="${filter}">
              <option value="${filter.key}">
                <c:out  value="${filter.key}"/>
              </option>
            </c:forEach>
       </select>
        <br/>
     <label for="SetValues">Values: </label>
         <select id="SetValues">
         //the part I don't know how to change according to the key selected
         </select>
      <input type="submit" value="Filter" class="search-button">
</form>

The question is: do I need javascript or can I do it whith passing and casting the object sent in the request, for example Map<String, Set<String>> filter= (HashMap<String, Set<String>>) request.getAttribute("servletName");, then iterate through it and prepare the two selects ?

Thanks.

Solution

The best approach to get your goal its

1. First iterate over all key of your Set and build the first dropdown

    <label for="Keys">Keys: </label>
      <select id="Keys" onchange="updateByKey()">
           <c:forEach var="filter" items="${filter}">
             <option value="${filter.key}">
               <c:out  value="${filter.key}"/>
             </option>
           </c:forEach>
      </select>
       <br/>
     <input type="submit" value="Filter" class="search-button">
   

2. Add an onChange event to the first dropdown and with every change make an ajax call to the server and retrieve the right values and build the second dropdown

   <label for="SetValues">Values: </label>
         //here load the dropdown with all options of the selected key in the previous dropdown
   <select id="SetValues">
       //iterate all options of this specific key
   </select>
   

Answered By - cralfaro
Answer Checked By - Pedro (JavaFixing Volunteer)