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Thinking in Java EE (At Least Trying To!)

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Thinking in Java EE (At Least Trying To!)

The CDI programming model isn't self-contained. But injecting the right beans will make it easier to think in Java EE. Here are a few.

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The CDI programming model has prerequisite requirements for beans which are lucky enough to leverage its services (DI, contextual state management etc.). This ranges from typical Java EE Managed Beans, EJB (session) beans etc. (I’ll leave the details for another post).

But the Good Thing is That

...it also provides some freebies i.e. beans which are available for injection by default

  • HttpSession
  • HttpServletRequest
  • ServletContext
  • UserTransaction
  • Principal

To be Noted

  • One can user either @Resource or the more obvious @Inject annotation to trigger injection
  • The @Default qualifier is applicable to injected instances of these beans
public class CDIFreebieResource {

    UserTransaction uTx;
    Principal actor;
    HttpSession httpSession;
    HttpServletRequest httpSR;
    ServletContext sCtx;

    public String get() throws Exception{
        "User Tx status: " + uTx.getStatus() + "\n" +
        "Principal: " + actor.getName() + "\n" +
        "HTTP Session ID: " + httpSession.getId() + "\n" +
        "HTTP Method: " + httpSR.getMethod() + "\n" + 
        "Context Path: " + sCtx.getContextPath();

Where can I Inject These Beans ?

Well, standard rules (defined by the CDI specification) apply here. I would recommend looking into the official Java EE Platform specification document (section EE 5.2.5, Table EE.5-1) which details this clearly. Here is a snapshot – Java EE managed beans, CDI managed beans, EJB, Servlet spec components, Web Socket endpoints, JSF managed beans etc.

Go on, check out the freebies …

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cdi ,java ,javaee

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