Learn JSTL

Question

Hi,
I used to have scriptlet in jsp page and normally use System.out.println to debug any jsp problems. Now I want to change them to use JSTL. Following I am trying to output all options and make one of selected:
      <% if(myBean.getOptions() != null) {
                  List list = myBean.getOptions();
                  for (int i=0; i < list.size(); i++) {
                       HashMap map = (HashMap)list.get(i);
                       String id = (String)map.get("id");
                       String description = (String)map.get("name");
      %>
      <option value="<%= id %>" <%= MiscUtil.optionSelected(id, myBean.getBookId())%>> <%= description %></option>
      <% } } %>I made it as:
<c:if test="${myBean.options}">
     <c:forEach var="item" items="#{myBean.options.items}">
          <c:set var="id" value="${item.value.id}"/>
          <c:set var="description" value="${item.value.name}"/>
      <option value="${ id }" <c:out value="DON'T KNOW HOW TO DO THIS"/>> ${ description }</option>
      </c:forEach>
</c:if>It shows empty list and don't know how to do default "select" in option. Maybe it's quite obviously wrong but can't really figure it out. How can I debug this? Thanks

Answer 1

Let me see if I understand your datastructures here:
You have a List that you iterate through
Each entry in the list is a map
The map has in it keys "id" and "value" which you want to display in the dropdown box.
The MiscUtil call looks to be a static method. My guess is that it wil return "selected" if the id is the same as myBean.getBookId()?
Lets take these one at a time:
First the forEach loop, the 'items' attribute should be your list (myBean.getOptions()) which translates to ${myBean.options}
Each 'item" will then be a Map.
map.get("id") can be written as ${map['id']} or just ${map.id}
similar for map.get("name");
This leads to the following code for rendering the dropdown list:
<c:forEach var="mapItem" items="${myBean.options}">
  <c:set var="id" value="${mapItem.id}"/>
  <c:set var="description" value="${mapItem.name}"/>
  <option value="${id}" >${description}</option>
</c:forEach>Next: the selected value.
There are two ways you could do this
1 - in JSTL with an if statement
<c:if test="${id == myBean.bookId}"> selected </c:if>2 - use a JSTL custom function tag to wrap the call to MiscUtil
In a tld file:
<taglib>
<function>
  <name>optionSelected</name>
  <function-class>com.mypackage.MiscUtil</function-class>
  <function-signature>
      java.lang.String optionSelected(java.lang.String, java.lang.String)
  </function-signature>
  </function>
</taglib>You would then import that tld into your jsp page (much like you do the JSTL)
Something like:
<%@ taglib prefix="misc" uri="http://MyMiscUtil"%>
and invoke it via
${misc:optionSelected(id, myBean.bookId}
The final thing:
<c:forEach var="mapItem" items="${myBean.options}">
  <c:set var="id" value="${mapItem.id}"/>
  <c:set var="description" value="${mapItem.name}"/>
  <option value="${id}" <c:if test="${id == myBean.bookId}"> selected </c:if>>${description}</option>
</c:forEach>Cheers,
evnafets
Edit: The forum is not displaying my last code example directly. It has added an extra > character between the value="${id} and the <c:if>
I can't seem to stop it doing that, so just be careful about copying/pasting that code ;-)
Or even better, reply and then select "quote original"
That will return you an undoctored version.