title: "javax.servlet.ServletException: Cannot find component" for <p:growl> component?
body: <p>I have the following Facelets code with an update on the <code>&lt;p:growl&gt;</code> component after the saving action.
  But I have the following exception while rendering the page :</p>
  
  <blockquote>
    <p>javax.servlet.ServletException: Cannot find component with expression ":principal:display" referenced from "mainForm:form1:j_idt27".</p>
  </blockquote>
  
  <pre><code>&lt;ui:define id="principal" name="content"&gt;
      &lt;p:growl id="display" showDetail="true" sticky="false" /&gt;
  
      &lt;p:panel header="Gestion de projets"&gt;
  
          &lt;h:form id="form1"&gt;
              &lt;h:panelGrid columns="3"&gt;
                  &lt;h:outputText value="Nom du projet: *" /&gt;
                  &lt;p:inputText value="#{gestionProjetBean.nomProjet}"
                      required="true" label="Nom du projet" /&gt;
                  &lt;p:commandButton value="Save"
                      actionListener="#{gestionProjetBean.creerProjet(gestionProjetBean.nomProjet)}"
                      update=":principal:display" /&gt;
              &lt;/h:panelGrid&gt;
          &lt;/h:form&gt;
  </code></pre>