How to select the first element of a set with JSTL?

StackOverflow https://stackoverflow.com/questions/1000876

  •  05-07-2019
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Question

I managed to do it with the next code but there must be an easier way. 

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>


<c:if test="${fn:length(attachments) > 0}">
    <c:forEach var="attachment" items="${attachments}" varStatus="loopCount">
        <c:if test="${loopCount.count eq 1}">
         attachment.id
        </c:if>
    </c:forEach>
</c:if>
Was it helpful?

Solution

You can access individual elements with the array [] operator:

<c:out value="${attachments[0].id}" />

This will work for arrays and lists. It won't work for maps and sets. In that case you must put the key of the element inside the brackets.

OTHER TIPS

Sets have no order, but if you still want to get the first element you can use the following:

<c:forEach var="attachment" items="${attachments}" end="0">
     <c:out value="${attachment.id} />
</c:forEach>

Work for arrays and lists only, not for set.

Since i have have just one element in my Set the order is not important So I can access to the first element like this :

${ attachments.iterator().next().id }

Look here for a description of the statusVar variable. You can do something like below, where the "status" variable contains the current status of the iteration. This is very useful if you need special annotations for the first and last iteraton. In the case below I want to ommit the comma behind the last tag. Of course you can replace status.last with status.first to do something special on the first itteration:

<td>
    <c:forEach var="tag" items="${idea.tags}" varStatus="status">
        <span>${tag.name not status.last ? ', ' : ''}</span>
    </c:forEach>
</td>

Possible options are: current, index, count, first, last, begin, step, and end

If you only want the first element of a set (and you are certain there is at least one element) you can do the following:

<c:choose>
    <c:when test="${dealership.administeredBy.size() == 1}">
        Hello ${dealership.administeredBy.iterator().next().firstName},<br/>
    </c:when>
    <c:when test="${dealership.administeredBy.size() > 1}">
        Hello Administrators,<br/>
    </c:when>
    <c:otherwise>
    </c:otherwise>
</c:choose>

You can use the EL 3.0 Stream API.

<div>${attachments.stream().findFirst().get()}</div>

Be careful! The EL 3.0 Stream API was finalized before the Java 8 Stream API and it is different than that. They can't sunc both apis because it will break the backward compatibility.

Using ${mySet.toArray[0]} does not work.

I do not think it is possible without having forEach loop at least one iteration.

Using begin and end seemed to work for me to select a range of elements. This gives me three separate lists. The first list with items 1-9, second list with items 10-18, and the last list with items 11-25.

                    <ul>
                        <c:forEach items="${actionBean.top25Teams}" begin="0" end="8" var="team" varStatus="counter">
                            <li>${team.name}</li>                               
                        </c:forEach> 
                    </ul>

                    <ul>
                        <c:forEach items="${actionBean.top25Teams}" begin="9" end="17" var="team" varStatus="counter">
                            <li>${team.name}</li>                               
                        </c:forEach> 
                    </ul>

                    <ul>
                        <c:forEach items="${actionBean.top25Teams}" begin="18" end="25" var="team" varStatus="counter">
                            <li>${team.name}</li>                               
                        </c:forEach> 
                    </ul>
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