JSF2: Passing a method in an EL expression

is it possible to pass a method in an EL expression?

I have one bean and two views. The second view has a button but which method the button triggers should be defined by the first view. So I have to tell the second view the method whe n I link from the first view.

I imagine something like this:

First View:

<h:link outcome="secondView.xhtml" value="Second view with method A">
    <f:param开发者_C百科 name="methodToCall" value="#{bean.methodA}">
</h:link>
<h:link outcome="secondView.xhtml" value="Second view with method B">
    <f:param name="methodToCall" value="#{bean.methodB}">
</h:link>

Second view:

<h:commandButton action="#{methodToCall}" value="Call the method" />

---

No, that's not possible. You can however invoke dynamic bean methods using the brace notation [].

<h:link outcome="secondView.xhtml" value="Second view with method A">
    <f:param name="methodToCall" value="methodA">
</h:link>
<h:link outcome="secondView.xhtml" value="Second view with method B">
    <f:param name="methodToCall" value="methodB">
</h:link>

with

<h:commandButton action="#{bean[param.methodToCall]}" value="Call the method" />

If the bean needs to be dynamic as well, you'll have to pass the bean name along separately and know its scope.

<h:link outcome="secondView.xhtml" value="Second view with method A">
    <f:param name="beanToCall" value="bean">
    <f:param name="methodToCall" value="methodA">
</h:link>
<h:link outcome="secondView.xhtml" value="Second view with method B">
    <f:param name="beanToCall" value="bean">
    <f:param name="methodToCall" value="methodB">
</h:link>

with

<h:commandButton action="#{requestScope[param.beanToCall][param.methodToCall]}" value="Call the method" />

---

I don't think there is a way to do this in JSF. My suggestion would be to have the call from the first view select a delegate in the backing bean which is called when clicking the action from the second view.

Something like this

public class Bean {

    public interface Delegate {
        void doSomething();
    }

    public class MethodADelegate implements Delegate {
        public void doSomething() {

        }
    }

    public class MethodBDelegate implements Delegate {
        public void doSomething() {

        }
    }

    private Delegate delegate;

    public String methodA() {
        this.delegate = new MethodADelegate();
        return "view2";
    }

    public String methodB() {
        this.delegate = new MethodBDelegate();
        return "view2";
    }

    public String view2Call() {
        delegate.doSomething();
        return "done";
    }
}

<h:commandLink action="#{bean.methodA}" value="Second view with method A" />
<h:commandLink action="#{bean.methodB}" value="Second view with method B" />

<h:commandButton action="#{bean.view2Call}" value="Call the method" />

---

Yes, it's possible. Here is the description for action attribute:

MethodExpression representing the application action to invoke when this component is activated by the user. The expression must evaluate to a public method that takes no parameters, and returns an Object (the toString() of which is called to derive the logical outcome) which is passed to the NavigationHandler for this application.