What is a CDI bean?

java jakarta-ee cdi
Yashar picture Yashar · Mar 20, 2013 · Viewed 25k times · Source

I am a little bit confused, we call CDI bean to the beans which we inject them using @Inject annotation or the beans which we use @Inject inside them ?

Answer

Mohanraj Balasubramaniam picture Mohanraj Balasubramaniam · May 3, 2017

CDI beans are classes that CDI can instantiate, manage, and inject automatically to satisfy the dependencies of other objects. Almost any Java class can be managed and injected by CDI.

For example, PrintServlet got dependency on a Message instance and have it injected automatically by the CDI runtime.

PrintServlet.java

@WebServlet("/printservlet")
public class PrintServlet extends HttpServlet {
    @Inject private Message message;

    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        response.getWriter().print(message.get());
    }
}

Message.java (This class is a CDI bean)

@RequestScoped
public class Message {
    @Override
    public String get() {
        return "Hello World!";
    }
}

Cheers!

Related questions

Why use @PostConstruct?

In a managed bean, @PostConstruct is called after the regular Java object constructor. Why would I use @PostConstruct to initialize by bean, instead of the regular constructor itself?

Read More
Should I use @EJB or @Inject

I have found this question: What is the difference between @Inject and @EJB but I did not get any wiser. I have not done Java EE before nor do I have experience with dependency injection so I do not understand …

Read More
wildfly: reading properties from configuration directory

I'm trying to read deployment specific information from a properties file in my wildfly configuration folder. I tried this: @Singleton @Startup public class DeploymentConfiguration { protected Properties props; @PostConstruct public void readConfig() { props = new Properties(); try { props.load(getClass().getClassLoader().getResourceAsStream("…

Read More