Assigning a Java Set to a Javascript array using EL

Question

So, I am trying to pass a Set into a .jsp page using Spring and JSP EL, and then assign the members of the set to a Javascript array to use later in client-side scripts.

For example, if I have the Java Set exampleSet: { "A", "B", "C"}

I pass it to the client side as part of a spring ModelandView object.

In the client-side JSP, I can use EL to output the set as ${model.exampleSet} , which gets parsed into [A, B, C] by JSP.

What I want to do is assign the contents of exampleSet to an array of javascript strings, so you get something like

var exampleSet = ["A", "B", "C"]

I can't find a direct way to do this. The other obvious approach to this is to loop through the Set, but as I can't work out the size of the Set in javascript, I don't think I can do this either.

You could use any one of a number of JSP tags that are designed to iterate over a collection, such as the JSTL <c:forEach> tag. — Anthony Grist
– Anthony Grist, Commented Aug 22, 2012 at 15:40
Anthony, thanks, I think that should work. Still wondering if there's a more elegant way to do it though. — RoryB
– RoryB, Commented Aug 22, 2012 at 15:45
Why is using JSTL to render your javascript not elegant? As mentioned by @mplungjan if you want to return just the JavaScript array as part of the response, you can write a JSON string to the response outputstream instead. But if you want a JavaScript array IN the HTML you probably already have, this is the way. — Rajesh J Advani
– Rajesh J Advani, Commented Aug 22, 2012 at 15:48
I was hoping to keep JSTL Tags out of my Javascript scripts, basically. — RoryB
– RoryB, Commented Aug 22, 2012 at 15:57

Rajesh J Advani · Accepted Answer · 2012-08-22 15:44:07Z

4

JavaScript executes on the browser. The JSP is rendered on the server. You're missing the lifetimes of the execution environments here.

What you would do is

<script>
var exampleSet = [
  <c:forEach var="item" items="${theSetVariable}" varStatus="loop">
    "${item}"
    <c:if test="${!loop.last}">,</c:if>
  </c:forEach>
]
<script>

So, you're looping through the Set in the JSP, to create the HTML/JavaScript, that creates code to represent the Javascript array when rendered on the browser.

answered Aug 22, 2012 at 15:44

Rajesh J Advani

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