Passing parameters between two jsf pages with parameter conversion

Question

I am a newbie on jsf i want to display the details of a question when i click on a h:link and to do so i need to pass the question id between two jsf pages (i have a detail page and another page that display a list of questions to display their details) but this id is of type Long so i need to convert it in order to be able to look for it in the database but i don't know how to do so.

I google it but the code i wrote after the search don't work. Here's the code

               <p:dataList value="#{questionBean.questionsForums}" var="quests"
                        itemType="none">
                        <p:panel >
                            <f:facet name="header">
                            <h:outputText value="#{quests.nbupvote}"
                                style="margin-right:30px;color:#cdcdcd" class="voteBox" />
                                <h:outputText class="font-custom" value="#{quests.titre}" />
                            </f:facet>
                            <h:link value="Consulter Détails" outcome="question">
                             <f:param name="quesId" value="#{quests.quesPk}"  >
                            </f:param> 
                            </h:link>
                            </p:panel>
                    </p:dataList>

and this the code of the managedBean

                  private String quesPk;
           private Question detailQuestion;

public Question getDetailQuestion() {
    return detailQuestion=qDao.selectDetail(Long.valueOf(quesPk));
}

public void setDetailQuestion(Question detailQuestion) {
    this.detailQuestion = detailQuestion;
}

And this in the log with the exception

                    2014-01-16T21:11:22.145+0100|Grave: Error Rendering View[/question.xhtml]
                    javax.el.ELException: /question.xhtml @52,24 value="#{questionBean.detailQuestion}": java.lang.NumberFormatException: null
at  com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:114)
at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:194)
at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:182)
at javax.faces.component.UIData.getValue(UIData.java:732)
                    Caused by: javax.el.ELException: java.lang.NumberFormatException: null
at javax.el.BeanELResolver.getValue(BeanELResolver.java:368)
at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176)
at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203)
at com.sun.el.parser.AstValue.getValue(AstValue.java:140)
at com.sun.el.parser.AstValue.getValue(AstValue.java:204)
at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:226)
at org.jboss.weld.el.WeldValueExpression.getValue(WeldValueExpression.java:50)
at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109)
... 53 more
                     Caused by: java.lang.NumberFormatException: null
at java.lang.Long.parseLong(Long.java:404)
at java.lang.Long.valueOf(Long.java:540)
at com.portail.managedBeans.QuestionBean.getDetailQuestion(QuestionBean.java:33)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606) 
                   2014-01-16T21:11:22.220+0100|Avertissement: StandardWrapperValve[Faces Servlet]: Servlet.service() for servlet Faces Servlet threw exception
                   java.lang.NumberFormatException: null
at java.lang.Long.parseLong(Long.java:404)
at java.lang.Long.valueOf(Long.java:540)
at com.portail.managedBeans.QuestionBean.getDetailQuestion(QuestionBean.java:33)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at javax.el.BeanELResolver.getValue(BeanELResolver.java:363)  

And this is the code of the details of the question

                         <h:head>
                         <f:metadata>
                        <f:viewParam name="quesId" value="#{questionBean.quesPk}" converter="javax.faces.Long" />
                          </f:metadata>
                           </h:head>

                         <h:form>

                    <p:dataList value="#{questionBean.detailQuestion}" var="quests"
                        itemType="none">
                    <h:outputText value="1" style="margin-right:30px;color:#cdcdcd"
                        class="voteBox" />
                    <h3><h:outputText class="font-custom"
                        value="#{quests.titre}" /></h3><br/><p:separator></p:separator>
                    <h:outputText class="font-custom"
                        value="#{quests.contenu}" />
                        <div class="navfooter" style="margin-left: 20%">
            <ul>
                <li><a href="profil.xhtml">Modifier</a></li>

                <li style="margin-left: 40%">Auteur</li>
            </ul>

        </div>
        </p:dataList>

I am using eclipse kepler and jsf2 and primefaces. If you know how it can be done please tell me

Answer 1

@ManagedProperty is not the right tool for the job of converting a submitted value and setting it as a bean property. HTTP request parameters are inherently strings. Better use <f:viewParam>, you can attach a converter to it like as you would do to <h:inputText>.

Source page:

<h:link value="Consulter Détails" outcome="question">
    <f:param name="quesId" value="#{quests.quesPk}" />
</h:link>

Target page (question.xhtml):

<f:metadata>
    <f:viewParam name="quesId" value="#{questionBean.quesPk}" converter="javax.faces.Long" />
</f:metadata>

With

private Long quesPk; // +setter

See also:

• ViewParam vs @ManagedProperty(value = "#{param.id}")
• What can <f:metadata>, <f:viewParam> and <f:viewAction> be used for?

---

Unrelated to the concrete problem, doing business logic in getter methods is a bad idea. Don't do that. Use <f:event type="preRenderView"> or <f:viewAction> listener method.

See also:

• Why JSF calls getters multiple times