I have the following piece of code:
<h:outputText value="#{lecture.lectureName}" />
<c:forEach items="#{criterionController.getCriteriaForLecture(lecture)}" var="criterion">
<h:outputText value="#{criterion.criterionName}" />
<h:commandLink value="Edit"/>
<h:commandLink value="Delete"/>
</c:forEach>
The output text part is working perfectly and displays what it should display so this proves that the lecture object is set. However the for each tag gives a null pointer exception. When I debugged the code, I saw that the lecture object was taken as null when the method getCriteriaForLecture() was called.
How can this behaviour explained?
This can happen if the lecturer variable is in turn been set by a JSF iterating component such as <h:dataTable>, <ui:repeat>, etc or probably a <p:tabView>, based on your previous question.
A more detailed explanation of this behaviour can be found here: JSTL in JSF2 Facelets... makes sense? To the point, JSTL tags runs during building the view, not during rendering the view. The lecturer variable is in your particular case only available during rendering the view and is thus always null during building the view, when JSTL runs.
To solve it, use a normal JSF component like <ui:repeat> instead.
<ui:repeat value="#{criterionController.getCriteriaForLecture(lecture)}" var="criterion">
<h:outputText value="#{criterion.criterionName}" />
<h:commandLink value="Edit"/>
<h:commandLink value="Delete"/>
</ui:repeat>
Much better would be not doing business actions in getters at all. Just make the List<Criterion> a property of Lecture instead.
<ui:repeat value="#{lecture.criterions}" var="criterion">
<h:outputText value="#{criterion.criterionName}" />
<h:commandLink value="Edit"/>
<h:commandLink value="Delete"/>
</ui:repeat>
See also Why JSF calls getters multiple times
Related
I have following code:
<ui:repeat var="class2" value="#{bean.list}" varStatus="status">
<h:form id="#{class2.name}">
<h:outputText value="#{class2.name}" />
</h:form>
</ui:repeat>
However, when I open the page, it errors as follows:
component identifier must not be a zero-length String
But it is properly printed in the <h:outputText>. How is this caused and how can I solve it?
You can use EL in the id attribute of a JSF component, but the EL variable has to be available during view build time, while the JSF component tree is to be built. However, the <ui:repeat> runs during view render time, while the HTML output is to be generated based on JSF component tree. The <ui:repeat var> is not available during view build time and #{class2.name} evaluates to null which totally explains the error you got. That it works in <h:outputText> is because it runs during view render time.
If you replace <ui:repeat> by <c:forEach>, which runs during view build time, then it'll work as you intented. The <c:forEach> will namely generate physically multiple <h:form> components in the JSF component tree which each generate individually their own HTML output (in contrary to <ui:repeat>, wherein the very same <h:form> component is been reused multiple times to generate HTML output).
<c:forEach var="class2" items="#{bean.list}" varStatus="status">
<h:form id="#{class2.name}">
<h:outputText value="#{class2.name}" />
</h:form>
</c:forEach>
However, I really wonder why you need to do that. There's usually no need to dynamically assign component IDs. JSF will already ensure the uniqueness of the ID. The below example,
<ui:repeat var="class2" value="#{bean.list}" varStatus="status">
<h:form id="form">
<h:outputText value="#{class2.name}" />
</h:form>
</ui:repeat>
will end up in multiple forms with each an unique ID, suffixed with iteration index of the <ui:repeat>. If you actually need to use #{class2.name} for some JavaScript/jQuery purposes (you did nowhere state the concrete functional requirement in the question for which you thought that this would be the right solution, so it's merely guessing), then just wrap it in a plain vanilla HTML element:
<ui:repeat var="class2" value="#{bean.list}" varStatus="status">
<div id="#{class2.name}">
<h:form id="form">
<h:outputText value="#{class2.name}" />
</h:form>
</div>
</ui:repeat>
Or set it as style class of a JSF component, which is also just selectable via a CSS selector:
<ui:repeat var="class2" value="#{bean.list}" varStatus="status">
<h:form id="form" styleClass="#{class2.name}">
<h:outputText value="#{class2.name}" />
</h:form>
</ui:repeat>
See also:
JSTL in JSF2 Facelets... makes sense?
I have following code:
<ui:repeat var="class2" value="#{bean.list}" varStatus="status">
<h:form id="#{class2.name}">
<h:outputText value="#{class2.name}" />
</h:form>
</ui:repeat>
However, when I open the page, it errors as follows:
component identifier must not be a zero-length String
But it is properly printed in the <h:outputText>. How is this caused and how can I solve it?
You can use EL in the id attribute of a JSF component, but the EL variable has to be available during view build time, while the JSF component tree is to be built. However, the <ui:repeat> runs during view render time, while the HTML output is to be generated based on JSF component tree. The <ui:repeat var> is not available during view build time and #{class2.name} evaluates to null which totally explains the error you got. That it works in <h:outputText> is because it runs during view render time.
If you replace <ui:repeat> by <c:forEach>, which runs during view build time, then it'll work as you intented. The <c:forEach> will namely generate physically multiple <h:form> components in the JSF component tree which each generate individually their own HTML output (in contrary to <ui:repeat>, wherein the very same <h:form> component is been reused multiple times to generate HTML output).
<c:forEach var="class2" items="#{bean.list}" varStatus="status">
<h:form id="#{class2.name}">
<h:outputText value="#{class2.name}" />
</h:form>
</c:forEach>
However, I really wonder why you need to do that. There's usually no need to dynamically assign component IDs. JSF will already ensure the uniqueness of the ID. The below example,
<ui:repeat var="class2" value="#{bean.list}" varStatus="status">
<h:form id="form">
<h:outputText value="#{class2.name}" />
</h:form>
</ui:repeat>
will end up in multiple forms with each an unique ID, suffixed with iteration index of the <ui:repeat>. If you actually need to use #{class2.name} for some JavaScript/jQuery purposes (you did nowhere state the concrete functional requirement in the question for which you thought that this would be the right solution, so it's merely guessing), then just wrap it in a plain vanilla HTML element:
<ui:repeat var="class2" value="#{bean.list}" varStatus="status">
<div id="#{class2.name}">
<h:form id="form">
<h:outputText value="#{class2.name}" />
</h:form>
</div>
</ui:repeat>
Or set it as style class of a JSF component, which is also just selectable via a CSS selector:
<ui:repeat var="class2" value="#{bean.list}" varStatus="status">
<h:form id="form" styleClass="#{class2.name}">
<h:outputText value="#{class2.name}" />
</h:form>
</ui:repeat>
See also:
JSTL in JSF2 Facelets... makes sense?
In my JSF page I use <c:choose><c:when> tag to conditionally display content. However, it does not work as it seems to always evaluate false.
E.g.
<h:outputText value="#{pollInfo.active} -" />
<c:choose>
<c:when test="#{pollInfo.active}">
<h:outputText value="Active" />
</c:when>
<c:otherwise>
<h:outputText value="Deactive" />
</c:otherwise>
</c:choose>
There are for sure a few items with active=true, which is confirmed by <h:outputText>, but it just prints Deactive for all items. You can see the actual output in the following picture:
How is this caused and how can I solve it?
The symptoms and the screenshot suggests that the #{pollInfo} represents the currently iterated item of an iterating UI component such as <ui:repeat>, <h:dataTable>, <p:tabView>, <p:dataTable>, etc.
JSTL tags run during view build time, that moment when JSF component tree is built based on XHTML source code. The var attribute of such an iterating UI component is only available during view render time, that moment when HTML output is produced based on JSF component tree.
In other words, they don't run "in sync". The #{pollInfo} is always null during view build time.
In this particular case, you need the JSF component's rendered attribute instead.
<h:outputText value="Active" rendered="#{pollInfo.active}" />
<h:outputText value="Deactive" rendered="#{not pollInfo.active}" />
Or if you intend to conditionally render larger pieces of code, wrap all in a <ui:fragment>:
<ui:fragment rendered="#{pollInfo.active}">
<h:outputText value="Active" />
<!-- Some more components here if necessary. -->
</ui:fragment>
<ui:fragment rendered="#{not pollInfo.active}">
<h:outputText value="Deactive" />
<!-- Some more components here if necessary. -->
</ui:fragment>
Again another alternative, given that you've a pure if-else, is using the conditional operator in EL:
<h:outputText value="#{pollInfo.active ? 'Active' : 'Deactive'}" />
Additional bonus is, you end up with much less code.
See also:
JSTL in JSF2 Facelets... makes sense?
This is the general structure of the jsf page:
<ui:repeat id="repeater" varStatus="stat" >
<h:form id="the-form">
<h:panelGroup id="renderme">
<ui:repeat id="inner-repeater">
<h:commandButton>
<f:ajax render=":repeater:#{stat.index}:the-form:renderme">
</h:commandButton>
</ui:repeat>
</h:panelGroup>
</h:form>
</ui:repeat>
So.. the button here, when clicked, should cause the element renderme to be re-rendered.
In practice, I get "component with id ... not found" although when I look at the html page, the generated id is correct.
Moreover, I tried to use #{component.parent.parent.clientId} which produced the same id and still got the same error message from JSF.
Any idea on why this is failing?
Thanks!
This doesn't work for the simple reason because viewRoot.findComponent("repeater:0:the-form:renderme") as requested by <f:ajax render> doesn't return anything. Such a component does not exist in the component tree. This ID only exists in the generated HTML output. Instead, it's viewRoot.findComponent("repeater:the-form:renderme") which would return something, but this does in turn not exist in HTML DOM tree where JavaScript needs to do the update based on ajax response. Even then, this is not exactly what you need.
This is where JSTL can come to rescue. It's capable of dynamically building the JSF component tree and of dynamically assigning IDs to components generated in a loop:
<c:forEach ... varStatus="stat">
<h:form id="the-form_#{stat.index}">
<h:panelGroup id="renderme">
<ui:repeat id="inner-repeater" ...>
<h:commandButton ...>
<f:ajax render=":the-form_#{stat.index}:renderme">
</h:commandButton>
</ui:repeat>
</h:panelGroup>
</h:form>
</c:forEach>
This will only cause problems when you bind <c:forEach> value to a view scoped bean and you use Mojarra version older than 2.1.18. You'd need to upgrade to at least Mojarra 2.1.18 then.
See also:
JSTL in JSF2 Facelets... makes sense?
I have a JSF 2 application with the following code:
<c:set var="number" value="0" scope="view" />
<ui:repeat value="${items}" var="item" varStatus="itemIndex">
<c:if test="${item.boolProperty == true}">
<c:set var="number" value="${number + 1}" scope="view" />
</c:if>
<h:outputText value="#{item.name}" />: <h:outputText value="#{number}" />
</ui:repeat>
I want to increase the number depending on the property of the item in the loop. However, the condition seems not to work, since the value of number always stays 0. If I remove the condition, the number is incremented only once, or it is always 0 before incrementing, therefore it outputs 1. Could it be possible the number var changes not to affect the number var that is outside the loop? I believe the scope attribute takes care of that.
JSTL tags and JSF components doesn't run in sync as you'd expect from the coding. JSTL tags runs during building of the JSF view, while JSF components runs during rendering of the JSF view. See for a detailed explanation also JSTL in JSF2 Facelets... makes sense?
What you want to achieve is unfortunately not possible with JSF components. The <ui:param> comes close, but it functions merely as an alias for a more complex EL expression, while the <c:set> actually sets something in the desired scope (the view scope which you've there is by the way wrong).
Your best bet is to change the model or wrap the model in another model so that you end up as
<ui:repeat value="${items}" var="item" varStatus="itemIndex">
<h:outputText value="#{item.name}" />: <h:outputText value="#{item.number}" />
</ui:repeat>