Question

I have a jsp page. if a user enters a certain text a ajax request is sent and and List is retrieved.Bow i want to built a drop down list from the List object and set the default value to the first element of the List Object. How I can do this.

Answer 1

I don’t have any AJAX knowledge so I cant help on that end. So my way of solving this would be doing the most I can in java/jsp’s and then using javascript/AJAX to fetch the select from an auxiliary jsp like this:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<select>
    <c:set var="seenFirst" value="0" />
    <c:forEach var="obj" items="${sessionScope.list}">
        <c:choose>
            <c:when test="${seenFirst == 0}">
                <c:set var="seenFirst" value="1" />
                <option value="${obj}" selected>${obj}</option>         
            </c:when>

            <c:otherwise>
                <option value="${obj}">${obj}</option>
            </c:otherwise>
        </c:choose>
    </c:forEach>
</select>

Edit:
Actually would be cleaner to build the menu first just with <c:forEach> using an auxiliary var to numerate the options (in the id field), then use javacript to turn on the selected attribute to the first one. Like this:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<select>
    <c:set var="n" value="0" />
    <c:forEach var="obj" items="${sessionScope.list}">
        <option id="menu-${n}" value="${obj}">${obj}</option>
        <c:set var="n" value="${n + 1}" />
    </c:forEach>
</select>

And you can use something like this to select the first element:

var first = document.getElementById('menu-0');
first.selected = true;