Question

How do I invoke/access a property of a managed bean when the bean name is known, but is not yet constructed?

For example:

<p:selectOneMenu value="#{eval.evaluateAsBean(bean).text}" >
    <f:selectItems value="#{eval.evaluateAsBean(bean).values}" var="val"
        itemLabel="#{val}" itemValue="#{val}" />
</p:selectOneMenu> 

If there is a managed bean called testBean and in my view bean has the "testBean"value, I want the text or values property of testBean to be called.

EDIT1

The context

An object consists of a list of properties(values). One property is modified with a custom JSF editor, depending on its type.

The list of editors is determined from the object’s type, and displayed in a form using custom:include tags. This custom tag is used to dynamically include the editors <custom:include src="#{editor.component}">. The component property points to the location of the JSF editor.

In my example some editors(rendered as select boxes) will use the same facelet(dynamicDropdown.xhtml). Every editor has a session scoped managed bean. I want to reuse the same facelet with multiple beans and to pass the name of the bean to dynamicDropdown.xhtml using the bean param.

genericAccount.xhtml

<p:dataTable value="#{group.editors}" var="editor">
    <p:column headerText="Key">
        <h:outputText value="#{editor.name}" />
    </p:column>
    <p:column headerText="Value">
        <h:panelGroup rendered="#{not editor.href}">
            <h:outputText value="#{editor.component}" escape="false" />
        </h:panelGroup>
        <h:panelGroup rendered="#{editor.href}">
            <custom:include src="#{editor.component}">
                <ui:param name="bean" value="#{editor.bean}"/>  
            <custom:include>
       </h:panelGroup>
    </p:column>
</p:dataTable>

#{editor.component} refers to a dynamicDropdown.xhtml file.

dynamicDropdown.xhtml

<ui:composition xmlns="http://www.w3.org/1999/xhtml"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:p="http://primefaces.prime.com.tr/ui">
    <p:selectOneMenu value="#{eval.evaluateAsBean(bean).text}" >
    <f:selectItems value="#{eval.evaluateAsBean(bean).values}" var="val"
        itemLabel="#{val}" itemValue="#{val}" />
    </p:selectOneMenu>  
</ui:composition>   

eval is a managed bean:

@ManagedBean(name = "eval")
@ApplicationScoped
public class ELEvaluator {
    ...

    public Object evaluateAsBean(String el) {
        FacesContext context = FacesContext.getCurrentInstance();
        Object bean = context.getELContext()
            .getELResolver().getValue(context.getELContext(), null, el);
        return bean;
    }

    ...

}

Answer 1

I am using servlet-api 2.5

Servlet 2.5 implies EL 2.1. Invoking methods with arguments is not supported in EL 2.1. It’s introduced in EL 2.2 which implies Servlet 3.0.

If you can’t upgrade to a Servlet 3.0 compatible container (Tomcat 7, Glassfish 3, JBoss AS 6, etc), then you need to upgrade the EL 2.1 implementation instead. JBoss EL is an EL 2.1 compatible implementation which supports the same new features as in EL 2.2. To install it, just drop jboss-el.jar in webapp’s /WEB-INF/lib and add the following context parameter to web.xml, assuming that you’re using Mojarra:

<context-param>     
    <param-name>com.sun.faces.expressionFactory</param-name>
    <param-value>org.jboss.el.ExpressionFactoryImpl</param-value>   
</context-param>