Question

I am starting in JSF2, comming from spring mvc, so I have some doubts that I cannot find answers on Core JavaServer Faces v3

Like this one…

How can the tag h:commandButton know which bean I am talking about ? I can only have one Bean per JSF page, is that it ? I am only giving it a msg.next which is a text from a i18n file.(quizbean is my bean)

<h:body>
<h:form>
    <h3>#{msgs.heading}</h3>
        <p>
            <h:outputFormat value="#{msgs.currentScore}">
                <f:param value="#{quizBean.score}"/>
            </h:outputFormat>
        </p>
        <p>#{msgs.guessNext}</p>
        <p>#{quizBean.current.sequence}</p>
        <p>
            #{msgs.answer}
            <h:inputText value="#{quizBean.answer}"/>
        </p>
        <p><h:commandButton value="#{msgs.next}"/></p>
</h:form>

Answer 1

The command button does not need to know this. All it generates is a HTML <input type="submit"> element. This is embedded in a HTML <form> with an action URL pointing to the same URL as the page. There’s further also the <input type="hidden" name="javax.faces.ViewState">. Thanks to this field, JSF knows exactly what view you’re submitting to. This view holds information about all inputs. This view knows that there’s an <h:inputText value="#{quizBean.answer}" />. The view knows the field name of the generated HTML <input type="text"> element. JSF will get the submitted request parameter value by request.getParameter() using this name and then update the answer property of the current instance of quizBean with this value.

Rightclick the page in your browser and choose View Source to see the JSF-generated HTML output. Put a breakpoint on ApplyRequestValuesPhase#execute() and HtmlBasicRenderer#decode() methods (assuming that you’re using Mojarra not MyFaces) to track the gathering of submitted values for every UIComponent in the view.