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

Question

I managed to do this with the following code, but there should 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> 

Answer 1

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

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

This will work for arrays and lists. It will not work for cards and sets. In this case, you must put the element key in brackets.

Answer 2

Sets the 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> 

Answer 3

Work only for arrays and lists, not for dialing.

Answer 4

Since I have only one element in my Set, the order is not important. Therefore, I can access the first element like this:

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

Answer 5

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

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

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

Answer 6

If you only need the first element in the set (and you are sure that 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> 

Answer 7

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

I do not think that this is possible without at least one iteration of the forEach loop.

Answer 8

Using the beginning and the end seemed to me useful to select a range of elements. This gives me three separate lists. The first list with items 1–9, the 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> 

Answer 9

You can use the EL 3.0 Stream API.

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

Be careful! The EL 3.0 Stream API has been modified to the Java 8 Stream API , and it is different from this. They cannot sunbathe both apis because they violate backward compatibility.