Inject a FlowScoped bean into a Jersey REST Web Service

Question

I'm developing an application that use a JSF flow to manage a wizard-like activity that can be started by a logged in user.

One page of the flow needs custom JavaScript code written in AngularJS, so I created a small Jersey REST service to exchange data between AngularJS and the bean (obviously the service should be called only when a user is using that flow page).

Inside the service I need the FlowScoped bean, but if I try to do

@Path("rest")
@RequestScoped
public class MyResource {

    @Inject
    MyFlowScopedBean myFlowScopedBean;

    // ...
}

The following exception is thrown:

exception java.lang.NullPointerException at com.sun.faces.flow.FlowCDIContext.getCurrentFlow

So, I'm using a session scoped bean associated to the user to retrieve the bean using the following workaround:

@Named
@FlowScoped("myFlow")
public class MyFlowScopedBean {

    @Inject
    UserDataBean userDataBean;

    @PostConstruct
    public void init() {
        userDataBean.setMyFlowScopedBean(this);
    }

    // ...
}

@Named
@SessionScoped
public class UserDataBean {

    private MyFlowScopedBean myFlowScopedBean;

    public getMyFlowScopedBean() {
        return myFlowScopedBean;
    }
    public setMyFlowScopedBean(MyFlowScopedBean myFlowScopedBean) {
        this.myFlowScopedBean = myFlowScopedBean;
    }

    // ...
}

@Path("rest")
@RequestScoped
public class MyResource {

    @Inject
    UserDataBean userDataBean;

    private MyFlowScopedBean getMyFlowScopedBean() {
        return userDataBean.getMyFlowScopedBean();
    }

    // ...
}

Is there a better way to do this? And, more important, should I do this or am I violating some best practices/conventions?

(I'm deploying on Glassfish 4.1)

Thanks!

Answer 1

Instead using JSF FlowScoped it is possible to obtain something very similar using ConversationScoped .

From the book "JBoss Weld CDI for Java Platform" by Ken Finnigan:

The conversation context implementation within Weld was developed to be used specifically with JSF. [...] In CDI 1.1, the tight coupling with JSF will be removed, enabling the conversation context to be used with other web frameworks.

Here a minimal working example (inspired by this blog post ):

@Named("foo")
@ConversationScoped
public class FooBean implements Serializable {

    @Inject
    Conversation conversation;

    public String getConversationId() {
        return conversation.getId();
    }

    @PostConstruct
    public void init() {
        conversation.begin();
    }

    // ...
}

@Path("foo")
@ConversationScoped
public class FooResource implements Serializable {

    @Inject
    FooBean fooBean;

    @GET
    @Path("myMethod")
    public String myMethod() {
        // ...
    }
}

In .xhtml:

<script>
    var CID = '#{foo.conversationId}'; // <-- EL
    $.get('/myApp/foo/myMethod?cid=' + CID);
</script>

Warning : pay attention using @FormParam : grizzly seems to have problems with it.

If you want a complete example about creating wizard using the conversation scope take a look at this post .