Why is service null in this call?

Question

I have this method on a bean:

public boolean isLinkInDescriptionForCheckbox(final Service service) {
    logger.info("Testing if there is a link for {}", service);
    return Service.UK_ADDRESS_CORRECTION == service;
}

...and this in my JSP:

<c:if test="#{serviceUiDescriptions.isLinkInDescriptionForCheckbox(service)}">

My log tells me this:

c.n.c.s.c.ServiceUiDescriptions - Testing if there is a link for null

And YET this works fine:

<label for="checkbox_#{service.name()}"> #{serviceUiDescriptions.getDescriptionForCheckbox(service)}</label>

...which is the line just before the c:if tag

So: In the line just before, service is not null, but in the test for the c:if line service is null.

Here's the whole fragment

<ui:repeat var="service" value="#{servicesBean.getAvailableServicesOfGroup(servicePresentationGroup)}">
    <div class="servicePresentation" title="#{serviceUiDescriptions.getLongDescription(service)}">
        <span class="checkboxSpan"> 
            <input type="checkbox” name="checkbox_#{service.name()}" value="true" checked="checked"
                                    id="checkbox_#{service.name()}" />
        </span>
            <h2>
                <label for="checkbox_#{service.name()}"> #{serviceUiDescriptions.getDescriptionForCheckbox(service)}</label>
                <c:if test="#{serviceUiDescriptions.isLinkInDescriptionForCheckbox(service)}">
                    <span class="smallText">
                        <h:outputLink value="#{serviceUiDescriptions.getLinkInDescriptionForCheckbox(service)}" >
                        #{serviceUiDescriptions.getLinkDescriptionInDescriptionForCheckbox(service)}
                        </h:outputLink>
                    </span>
                </c:if>
            </h2>
        </div>
</ui:repeat>

This is what I get - look no link:

look no link

Is `servicesBean.getAvailableServicesOfGroup(servicePresentationGroup)` null? JSP's expression language is ["null friendly"](http://stackoverflow.com/questions/15446632/el-and-cout-prints-empty-string-for-null-attributes-but-throws-exception-when) so `service.name()` will not raise an exception even if `service` is null, but as soon as you pass something back into Java land, you need to be careful about dereferencing null. — Mike Samuel, May 07 '14 at 19:41
for my dollar, this looks like JSF. If it is JSF, consider immediate evaluation for the test condition ('test="${blah') instead of delayed (not sure that is the correct term) 'test="#{blah'. — DwB, May 07 '14 at 19:43
@MikeSamuel the available services is not null. serviceUiDescriptions.getLongDescription(service) does not get a null a little higher up. — Anders Johansen, May 07 '14 at 19:46

score 2 · Accepted Answer · edited May 23 '17 at 11:57

Both statements may be one line after another but they are not executed at the same time. <c:if> is a JSTL-Tag which is executed during view build time. The other expression will be wrapped in a <h:outputText> which will be executed during view render time. And I guess the service will be created in between.

To solve your problem you could replace the <c:if> with

<ui:fragment rendered="#{serviceUiDescriptions.isLinkInDescriptionForCheckbox(service)}">

or replace the <span> element with

<h:panelGroup styleClass="smallText" rendered="#{serviceUiDescriptions.isLinkInDescriptionForCheckbox(service)}">

(without the <c:if>).

Why is service null in this call?

1 Answers1