JSF2: How to initiate services at deployment

Question

For university project I am developing a webapplication with JSF. My excercise is to do the frontend. A fellow studend is supposed to do backend stuff. Both parts are designed to be seerate applications. Both communicate through RMI. I want to open the connection once at deployment.

I am at the point to settle up the connection now. I tried to do that with a @ApplicationScoped ManagedBean:

//Constructor of ApplicationScoped ManagedBean  
public Communication() {
    this.connect();
}

Is that way possible? I tried it but the managedBean seems not to be called..

Can you advice a Best Practice?

@Brian: Unfortunately I don't use EJB at all -.-

@BalusC's pot: I created a communicationbean:

@ManagedBean(name="communication")
@ApplicationScoped
public class Communication {

    public static FrontendCommInterface server;

    public Communication() {
        this.connect();
    }

Then I created the LoginBean:

@ManagedBean
@ViewScoped
public class Login {

@ManagedProperty(value="#{communication}")
private Communication communicationBean;

public FrontendCommInterface server;

private String username;
private String password;

public Login() {
    server = communicationBean.getConnection();
}

public String login(){
    HttpSession session = (HttpSession) FacesContext.getCurrentInstance().getExternalContext().getSession(true);
    String sessionId = session.getId();

    try {
        server.login(getUsername(), getPassword(), sessionId);
        return "start.xhtml";

    } catch (RemoteException e) {
        e.printStackTrace();
        FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_ERROR,"Anmeldung nicht erfolgreich: ", getUsername()+", "+getPassword()+", "+sessionId));
        return "login.xhtml";
    }
}

But unfortunately it throws exceptions:

com.sun.faces.mgbean.ManagedBeanCreationException: Klasse org.dhbw.stg.wwi2008c.mopro.ui.managedBeans.Login can not be instanciated.

java.lang.NullPointerException
    org.dhbw.stg.wwi2008c.mopro.ui.managedBeans.Login.<init>(Login.java:28)

After debuging I found out that my ManagedProperty is Null ! It hasn't been created! How to do that? I thought referencing via managedproperty would create it -.-

score 2 · Accepted Answer · answered Jan 05 '11 at 16:38

The managed bean is only auto-created whenever it's been referenced by EL #{managedBeanName}, which can happen by either accessing as-is in view, or by being injected as managed property of another bean, or being manually EL-resolved by e.g. Application#evaluateExpressionGet().

In your particular case, you actually want to intialize some stuff during webapp's startup. You rather want to use ServletContextListener for this.

@WebListener
public class Config implements ServletContextListener {

    public void contextInitialized(ServletContextEvent event) {
        // Do stuff during webapp's startup.
    }

    public void contextDestroyed(ServletContextEvent event) {
        // Do stuff during webapp's shutdown.
    }

}

You could even pre-create an application scoped managed bean there whenever necessary (if your intent is to be able to access it from other beans by @ManagedProperty).

    public void contextInitialized(ServletContextEvent event) {
        event.getServletContext().setAttribute("bean", new Bean());
    }

JSF stores application scoped beans as an attribute of the ServletContext and JSF won't auto-create another one when one is already present, so the one and the same as created by the above code example will be used by JSF as well.

tried the easy way and put a managedProperty in there but that didn 't work -.- — Sven, Jan 09 '11 at 11:22
Managed properties are set *after* bean's construction, not *before*. You need `@PostConstruct` to access them. Replace `public Login()` by `@PostConstruct public void init()`. — BalusC, Jan 09 '11 at 12:05

score 0 · Answer 2 · answered Jan 09 '11 at 05:19

If you can use EJB 3.1 lite {1} in your web app, then you can use a Singleton Session Bean, annotated with @Startup, and a @PostConstruct method. I have one that looks like:

@Singleton
@Startup
public class CachePrimer {

    @PostConstruct
    public void loadOpenRequests() {
         ...
    }
}

{1}: EJB 3.1 lite is included in the Web Profile of JavEE 6, and is provided by web profile servers like Glassfish, JBoss 6, and Resin. When using such a web profile server, you simply include your EJBs in your .war file, no additional work is required.

JSF2: How to initiate services at deployment

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