<f:viewParam> not being set during <h:form> submit

Question

I would like to create a form to simply modify the fields of some project entity.

To do so I created a request scoped bean and a view that uses together with a converter to tell the bean which entity is being edited.

Bean

@Named
@RequestScoped
public class Bean {

    private Project selectedProject;

    public void setSelectedProject(Project project) {
        selectedProject= project;
    }

    public Project getSelectedProject() {
        return selectedProject;
    }

    public String save() {
        // Persist selectedProject...
        return null;
    }
}

View

<ui:composition template="/templates/layout.xhtml"
    xmlns="http://www.w3.org/1999/xhtml"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:p="http://primefaces.org/ui">

<ui:define name="metadata">
    <f:metadata>
        <f:viewParam id="projectParam" name="project"
            value="#{bean.selectedProject}" converter="#{projectConverter}" />
    </f:metadata>
</ui:define>

<ui:define name="content">
    <h:form id="projectForm">

        <p:panel header="Project details">
            <h:panelGrid columns="2">

                <p:outputLabel for="title" value="Title" />
                <h:inputText id="title" value="#{bean.selectedProject.title}" />

                <p:outputLabel for="desc" value="Description" />
                <h:inputTextarea id="desc" value="#{bean.selectedProject.description}" />

            </h:panelGrid>

            <p:commandButton id="submitButton" type="submit"
                value="Save" action="#{bean.save}">
                    <f:param name="project" value="#{bean.selectedProject.id}" />
            </p:commandButton>

        </p:panel>

    </h:form>

</ui:define>
</ui:composition>

Loading the view initially works fine, the chosen project is loaded and the form fields are filled with the project's properties. However when saving the form I receive the following stack trace:

11:00:58,837 WARNING [javax.enterprise.resource.webcontainer.jsf.lifecycle] (http--0.0.0.0-8080-3) /user/project.xhtml @42,70 value="#{bean.selectedProject.title}": Target Unreachable, 'selectedProject' returned null: javax.el.PropertyNotFoundException: /user/project.xhtml @42,70 value="#{bean.selectedProject.title}": Target Unreachable, 'selectedProject' returned null
    at com.sun.faces.facelets.el.TagValueExpression.getType(TagValueExpression.java:100) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getConvertedValue(HtmlBasicInputRenderer.java:95) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at javax.faces.component.UIInput.getConvertedValue(UIInput.java:1030) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIInput.validate(UIInput.java:960) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIInput.executeValidate(UIInput.java:1233) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIInput.processValidators(UIInput.java:698) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at org.primefaces.component.panel.Panel.processValidators(Panel.java:297) [primefaces-3.5.jar:]
    at javax.faces.component.UIForm.processValidators(UIForm.java:253) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at org.primefaces.component.layout.Layout.processValidators(Layout.java:246) [primefaces-3.5.jar:]
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1172) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) [jsf-impl-2.1.7-jbossorg-2.jar:]
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
    at org.jboss.weld.servlet.ConversationPropagationFilter.doFilter(ConversationPropagationFilter.java:62) [weld-core-1.1.5.AS71.Final.jar:2012-02-10 15:31]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:489) [jbossweb-7.0.13.Final.jar:]
    at org.jboss.as.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
    at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:153) [jboss-as-web-7.1.1.Final.jar:7.1.1.Final]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [jbossweb-7.0.13.Final.jar:]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368) [jbossweb-7.0.13.Final.jar:]
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877) [jbossweb-7.0.13.Final.jar:]
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:671) [jbossweb-7.0.13.Final.jar:]
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:930) [jbossweb-7.0.13.Final.jar:]
    at java.lang.Thread.run(Thread.java:680) [classes.jar:1.6.0_51]

While debugging the problem I found out that the converter is indeed called, but the returned project is not set on the bean before the above lifecycle occurs. If I return a dummy project in the bean, everything works fine, the selected project is eventually set I can be persisted with the updated values.

Is this expected behaviour? Can I get this running without returning a dummy project?

I've seen approaches with view scoped beans. Since we're using CDI I'd prefer to stick to javax.enterprise annotations. If you think the rest of the code (template, converter) are of any relevance I'm happy to add them.

Answer 1

It is an expected behaviour. With <f:viewParam /> you're setting the value in the bean during GET request. Value is set, that's why your page is rendered properly, however your bean is @RequestScoped, so its state is lost from one request to the other one. When you perform the POST request with your p:commandButton, its value is actually null. To solve it, you should use @ViewScoped bean.