How to use if, else condition in jsf to display image

Question

I have a condition where I have an enrollment form in which if userid is 0 it should show the dummy image and when I edit user from any update, I check for if userid which is not equal to 0 then display the image corresponding to userid.

I used JSTL inside jsf page. But always it tries to go to else loop for showing image. The functionality is working fine. The only thing is I can't display the dummy image when I visit the page first. Here s my code.:

<c:if test="${'#{user.userId}' == '0'}">
  <a href="Images/thumb_02.jpg" target="_blank" ></a>
  <img src="Images/thumb_02.jpg" />
</c:if>
<c:otherwise>
  <a href="/DisplayBlobExample?userId=#{user.userId}" target="_blank"</a>
  <img src="/DisplayBlobExample?userId=#{user.userId}" />
</c:otherwise>

Can I use this JSTL tag or can I do it using jsf?

score 57 · Answer 1 · answered Apr 02 '14 at 09:19

57

For those like I who just followed the code by skuntsel and received a cryptic stack trace, allow me to save you some time.

It seems c:if cannot by itself be followed by c:otherwise.

The correct solution is as follows:

<c:choose>
    <c:when test="#{some.test}">
        <p>some.test is true</p>
    </c:when>
    <c:otherwise>
        <p>some.test is not true</p>
    </c:otherwise>
</c:choose>

You can add additional c:when tests in as necessary.

answered Apr 02 '14 at 09:19

jmkgreen

1,633
14
22

It's great you've written an update! Just corrected my answer so that it'd compile as well. It's sometimes helpful to reread your answer. – skuntsel Sep 19 '14 at 15:28
It's also worth noting that some.test needs to not evaluate to false during the apply request values phase. See here for more (point 5): https://stackoverflow.com/questions/2118656/commandbutton-commandlink-ajax-action-listener-method-not-invoked-or-input-value – Sam Apr 10 '18 at 13:41
I believe to use the h:outputText component is better, check this answer: https://coderanch.com/t/213739/java/JSTL-tag-working-JSF-page – Hazim May 19 '22 at 11:03

score 39 · Accepted Answer · edited Jun 14 '20 at 13:24

It is illegal to nest EL expressions: you should inline them. Using JSTL is perfectly valid in your situation. Correcting the mistake, you'll make the code working:

<html xmlns="http://www.w3.org/1999/xhtml" xmlns:c="http://java.sun.com/jstl/core">
    <c:if test="#{not empty user or user.userId eq 0}">
        <a href="Images/thumb_02.jpg" target="_blank" ></a>
        <img src="Images/thumb_02.jpg" />
    </c:if>
    <c:if test="#{empty user or user.userId eq 0}">
        <a href="/DisplayBlobExample?userId=#{user.userId}" target="_blank"></a>
        <img src="/DisplayBlobExample?userId=#{user.userId}" />
    </c:if>
</html>

Another solution is to specify all the conditions you want inside an EL of one element. Though it could be heavier and less readable, here it is:

<a href="#{not empty user or user.userId eq 0 ? '/Images/thumb_02.jpg' : '/DisplayBlobExample?userId='}#{not empty user or user.userId eq 0 ? '' : user.userId}" target="_blank"></a>
<img src="#{not empty user or user.userId eq 0 ? '/Images/thumb_02.jpg' : '/DisplayBlobExample?userId='}#{not empty user or user.userId eq 0 ? '' : user.userId}" target="_blank"></img>

Not only does this result in (almost) duplicated code but also doubled evaluation time. Consider `c:choose + c:when + c:otherwise` instead. — Quoting Eddie, Dec 07 '17 at 12:48

score 8 · Answer 3 · answered Sep 03 '15 at 17:19

Instead of using the "c" tags, you could also do the following:

<h:outputLink value="Images/thumb_02.jpg" target="_blank" rendered="#{not empty user or user.userId eq 0}" />
<h:graphicImage value="Images/thumb_02.jpg" rendered="#{not empty user or user.userId eq 0}" />

<h:outputLink value="/DisplayBlobExample?userId=#{user.userId}" target="_blank" rendered="#{not empty user and user.userId neq 0}" />
<h:graphicImage value="/DisplayBlobExample?userId=#{user.userId}" rendered="#{not empty user and user.userId neq 0}"/>

I think that's a little more readable alternative to skuntsel's alternative answer and is utilizing the JSF rendered attribute instead of nesting a ternary operator. And off the answer, did you possibly mean to put your image in between the anchor tags so the image is clickable?

How to use if, else condition in jsf to display image

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