How to inject a http session attribute to a bean using CDI - jsf

Question

I have some legacy code that put objects as http session attributes using code like this:
MyObject object = new MyObject();
Map<String, Object> sessionMap = FacesContext.getCurrentInstance().getExternalContext().getSessionMap();
sessionMap.put("attrname", object);
The old facelets accessed the code using
#ManagedProperty("#{attrname}")
private MyObject object;
Is there any way using CDI (#Inject) to inject this session attribute to a Bean?
In new code that uses CDI what's the better way to create and inject objects that need to be created in a controlled way.

Answer 1

Get hold of it in a session scoped managed bean with a #Produces#Named on the getter.
#SessionScoped
public class MyObjectProducer implements Serializable {
private MyObject myObject;
#Produces
#Named("attrname")
public MyObject getMyObject() {
return myObject;
}
public void setMyObject(MyObject myObject) {
this.myObject = myObject;
}
}
When you set it somehow via e.g. myObjectProducer.setMyObject(myObject) elsewhere (or perhaps a CDI #Observes event), then you can inject it anywhere using #Inject #Named.
#Inject
#Named("attrname")
private MyObject myObject;
And yes, it's still available via #{attrname} in EL the usual way. And no, it won't be auto-created when not set, it'll remain null until you actually set it as a property of the producer class.
Alternatively, if you really intend to keep the legacy way of setting the instance via ExternalContext#getSessionMap() (e.g. because it's third party and you can thus not change it), then you can alternatively also let the producer return it directly from the session map:
#SessionScoped
public class MyObjectProducer implements Serializable {
#Produces
#Named("attrname")
public MyObject getMyObject() {
return (MyObject) FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get("attrname");
}
}
This however isn't guaranteed to work when injected in a non-JSF artifact, such as an arbitrary #WebServlet, as the FacesContext#getCurrentInstance() would obviously return null.

Answer 2

This is the way to go, for both non-jsf and jsf artifacts.
#Qualifier
#Retention(RUNTIME)
#Target({TYPE,METHOD,FIELD,PARAMETER});
public #interface SessionAttribute {
#NonBinding
String value() default "";
}
#ApplicationScope
public class SessionAttributeService {
//Dont worry, this is a proxy, and CDI will ensure that the right one called at the right time.
#Inject
private HttpServletRequest servletRequest;
#Produces
#SessionAttribute
#RequestScope
public String sessionAttribute(final InjectionPoint ip){
final SessionAttribute sa = ip.getAnnotated().getAnnotation(SessionAttribute.class);
final HttpSession session = servletRequest.getSession();
return session.getAttribute(sa.value());
}
}
And use case:
#RequestScope
public class MyServiceBean {
#Inject
#SessionAttribute("theAttribute")
private String attribute;
}