JSF/CDI dependency injection into ActionListener

Question

Why CDI don't inject my backing bean (session scope) in this ActionListener? The loginBean instance is always null. I have the impression that CDI does not manage the listener instances : it's right?

import javax.faces.event.AbortProcessingException;
import javax.faces.event.ActionEvent;
import javax.inject.Inject;

public class CancelListener implements javax.faces.event.ActionListener {

    private LoginBean loginBean; 

    @Inject
    public void setLoginBean(LoginBean loginBean) {
        this.loginBean = loginBean;
    }

    @Override
    public void processAction( ActionEvent event ) throws AbortProcessingException {
        loginBean.setLogin( "" );
        loginBean.setPassword( "" );
    }

}

Here the definition of my LoginBean class.

import java.io.Serializable;

import javax.enterprise.context.SessionScoped;
import javax.faces.event.ActionEvent;
import javax.inject.Named;


@Named
@SessionScoped 
public class LoginBean implements Serializable {

    private static final long serialVersionUID = -5433850275008415405L;

    private String login = "james@mi6.uk";
    private String password = "007";

    public String getLogin() {
        return login;
    }

    public void setLogin(String login) {
        this.login = login;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

}

And my listener is connected to the button with this code :

<h:commandButton value="Cancel" immediate="true">
    <f:actionListener type="mypackage.CancelListener" />
</h:commandButton>

I know that i can use a method directly on the backing bean (connected with actionListener tag attribute), but I would like to understand how to make my class compatible with CDI and how to force the injection in this case. Thanks in advance.

Normally, the setter is not mandatory and CDI can directly inject into a private attribute (using reflexion). I have added the setter but the result is the same. — Koor.fr, Dec 28 '18 at 14:30
Why do you need to implement `ActionListener` interface? Usually you can define a bean method as `actionListener` in a UIComponent as explained in any JSF basic tutorial — perissf, Dec 28 '18 at 14:55
Because CancelListener is not a CDI or JSF managed bean. It's just a class that implements `ActionListener` interface. Not a bean. — perissf, Dec 28 '18 at 15:06
Ok. But how can i said to CDI to manage event listeners (CancelListener instances)? — Koor.fr, Dec 28 '18 at 15:18
Which jsf/cdi tutorial are you using? There us no indication your 'bean' is a managed bean at all, not is the scope visible/declared and you rarely need to implement the `ActionListener` interface. In normal applications not at all even. [mcve] please... — Kukeltje, Dec 28 '18 at 15:54

perissf · Accepted Answer · 2018-12-28T19:27:04.997

You haven't explained why you need to use a bean that implements the ActionListener interface, instead of using a method qualifier as actionListener attribute inside the UIComponent.

As you seem to have already tried, making CancelListener a CDI bean is not enough for having it instantiated correctly: LoginBean will be null.

However, using the binding attribute will force JSF to dynamically instantiate the bean, and this will make the trick:

<h:commandButton value="Cancel" immediate="true">
    <f:actionListener binding="#{cancelListener}" type="mypackage.CancelListener" />
</h:commandButton>

As mentioned above, the class implementing ActionListener must be a CDI bean as well:

@Named
@SessionScoped
public class CancelListener implements Serializable, javax.faces.event.ActionListener {

    @Inject
    private LoginBean loginBean;

    @Override
    public void processAction(ActionEvent event) throws AbortProcessingException {
        System.out.println(this.toString());
        System.out.println(loginBean.toString());
    }        
}

See also:

How does the 'binding' attribute work in JSF? When and how should it be used?

JSF/CDI dependency injection into ActionListener

1 Answers1