Nesting EL expressions in core tags

Question

Hi all,
I have a situation where I require to use dymanic textboxes based on the certain criteria. To make this work I used strut's LazyValidatorActionForm. It works like a charm but when I want to write out certain form property using EL, it doesn't work well. I am not sure how to use it with <c:out />. For example:
This is the code I tried to display a link with a value in the dynamic form:
<c:forEach var="counter" begin="0" end="${numTextFields}" >
?methodToCall=removeElement&id=<c:out value="${request['FAEditorForm'].id_${counter}}" />">Remove</a>
</c:forEach>
Here, I am trying to get the Form from the request attribute and invoke the method for property 'id_?' where '?' can be some number depending on the counter in the loop. When executing this page, I am getting an exception:
javax.servlet.jsp.JspException: Can't insert page '/pages/findingaids/FACustomContainerEditor.jsp' : javax.servlet.jsp.JspException: The taglib validator rejected the page: "tag = 'out' / attribute = 'value': An error occurred while parsing custom action attribute "value" with value "${request['FAEditorForm'].id_${counter}}": Encountered "{", expected one of ["}", ".", ">", "gt", "<", "lt", "==", "eq", "<=", "le", ">=", "ge", "!=", "ne", "[", "+", "-", "*", "/", "div", "%", "mod", "and", "&&", "or", "||"], "
I also tried using <c:set /> but looks like the JSTL tags does not allow nesting EL ('{') inside another EL. Not sure how to solve this issue. Any help is appreciated.
Thanks,
Srini

Answer 1

To solve the nested EL expression issue, you use the square brackets notation.
This should be close to what you want.
<c:forEach var="counter" begin="0" end="${numTextFields}" >
  <c:set var="cVar" value="id_${counter}"/>
  <c:out value="${FAEditorForm[cVar]"/>
</c:forEach>However instead of building the parameter string manually, you should let the struts tag do it for you.
Seeing as you have two parameters, you have to pass it a map.
<jsp:useBean id="paramMap" class="java.util.HashMap" scope="page"/>
<c:set target="${paramMap}" property="methodToCall" value="removeElement"/>
<c:forEach var="counter" begin="0" end="${numTextFields}" >
  <c:set var="cVar" value="id_${counter}"/>
  <c:set target="${paramMap}" property="id" value="${cVar}"/>
  <html:link page="/FAEditor.do" name="paramMap">Remove </html:link>
  <br>...
</c:forEach>Cheers,
evnafets