Question

Take the following JSP fragment:

<c:forEach items="${items}" varStatus="status">
   ${'A' + status.index}
</c:forEach>

The intent should clear, I’m trying to generate an ‘A’-based character index for each iterations through the loop. In Java, this is fine (e.g. 'A' + 1 == 'B'), but JSP EL on Tomcat 6 barfs with java.lang.NumberFormatException: For input string: "A". It seems it cannot handle characters as ordinal values.

The current solution breaks this out into a custom taglib, but this is absurd for something so trivial.

Can anyone see how to persuade EL to do this calculation?

Answer 1

First create the alphabet:

<c:set var="alphabet" value="ABCDEFGHIJKLMNOPQRSTUVWXYZ"/>

Then you can use fn:substring to access letters.

${fn:substring(alphabet, status.index, status.index + 1)}

Your example would become:

<c:forEach items="${items}" varStatus="status">
    <c:set var="indexOfLetter" value="${fn:indexOf('A', alphabet) + status.index}"/>
    ${fn:substring(alphabet, indexOfLetter, indexOfLetter + status.index + 1}
</c:forEach>

You’ll probably need some edge case checking, but this should work.