Trouble making a Javascript array using JSP

Question

I find JSP works great in HTML but I often have problems using it to generate Javascript. This code isn't working, and in fact the page crashes when I try to inspect the element with Chrome's debugging tools:

var sensorData = [[
                        <c:forEach items="${tableData}" var="val" varStatus="status">
                            <c:set var="tempStr" value="X"/>

                            <c:choose>
                                <c:when test="${!fn:contains(val, tempStr)}">
                                    <fmt:formatNumber value="${val}" maxFractionDigits="0"/>
                                </c:when>
                                <c:otherwise>
                                    ${val}
                                </c:otherwise>
                            </c:choose>

                            <c:choose>
                                <c:when test="${(status.index + 1) % width == 0 && !status.last}">
                                    ],[
                                </c:when>
                                <c:when test="${status.last}">
                                    ]
                                </c:when>
                                <c:otherwise>
                                    ,
                                </c:otherwise>
                            </c:choose>


        </c:forEach>
                 ];

Here I'd like to create a 2d array with tableData, an ArrayList. Eclipse is showing errors on the first <c:when>:

Syntax error, insert "]" to complete ArrayLiteral

Can anyone see what I'm doing wrong?

I don't see anything obvious, but you don't say what those values look like. You might try it in Firefox/Firebug, or the "Tamper Data" Firefox plugin, so that you can look at exactly what that code generates and figure out what's wrong with it. — Pointy
– Pointy, Commented Jun 16, 2011 at 14:47
@Ravi Parekh well it's true that when the list is empty he'll end up with "[[]", but it looks OK so long as it's not empty. — Pointy
– Pointy, Commented Jun 16, 2011 at 14:48
I'd ignore that Eclipse error message - it's just being stupid. — Pointy
– Pointy, Commented Jun 16, 2011 at 14:48
Why don't you use a library like Jackson to generate JSON for you? You can stick the resultant JSON to the right-hand side of your assignment. jackson.codehaus.org — Ateş Göral
– Ateş Göral, Commented Jun 16, 2011 at 14:51
tableData is an ArrayList of Strings. I just printed it on the server and it looks good. The values are like this: [X,X,X,123.123,2345.235,X,X,455.445,X,...]. I have an error on the page that says: Uncaught ReferenceError: X is not defined (chrome) — Tony R
– Tony R, Commented Jun 16, 2011 at 14:57

Pointy · Accepted Answer · 2011-06-16 15:00:19Z

1

If some of the array values are strings, then that's you're problem — you have to quote them.

        <c:otherwise>
            "${val}"
        </c:otherwise>

Now you're also going to have to worry about string values that contain quotes and other meta-characters in JavaScript's string constant token syntax. I use my own EL function for "protecting" string contents, kind-of analogous to fn:escapeXml(). Unfortunately Java is frozen in time so there's no built-in support for generating JSON, which would obviate this entire exercise. (I also have my own EL function for that, of course, because it's really not very hard for non-exotic data structures.)

answered Jun 16, 2011 at 15:00

Pointy

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1 Comment

Tony R Over a year ago

Bah you're right! Well this is why I don't like using JSP in Javascript... Anyway, I solved the problem using google-gson and it's working now, thanks everyone!

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