As mentioned earlier, the Managed Beans specification was introduced in Java EE 6 to provide a common definition of a Managed Bean. All that's required to create a Managed Bean is to annotate it with @ManagedBean, though CDI doesn't require us to do so.

Earlier in this chapter, we covered the requirements for constructors of a Java class to be a Managed Bean, but the CDI specification states that it must also meet the following conditions:

According to the preceding conditions, Java Persistence API (JPA) entities are also Managed Beans! Trying to use entities as Managed Beans will cause runtime issues when attempting to persist Managed Beans that have been proxied by CDI.

Session Beans can take advantage of CDI just like any other bean, though there are a few restrictions due to Session Beans having their lifecycle managed separate to CDI.

Message-driven and entity beans are not contextual objects in the CDI sense, so they are not able to be injected into other beans. It is possible to inject beans into a message-driven bean, and use interceptors and decorators to utilize some of the CDI functionalities that are available.

As the EJB container controls the lifecycle of a stateless Session Bean and a singleton Session Bean, there is no need to specify any CDI scope for these, but a stateful Session Bean may use any scope it requires.

In these final two sections, we will introduce producers, both method and field, which can be used to provide a CDI bean that isn't a Java class, per se. Producers are often useful in a situation where it is not known during development which particular qualified bean instance needs to be used, and producers allow us to create a bean that depends on runtime information for its creation.

Producers provide a source for new bean instances. A producer will be invoked by Weld when there is no instance of that bean in the required context.

We will cover producers in detail in Chapter 5, Producers.

public class AccountManager {
  @Produces
  @User
  Account getUserAccount() {
    ...
  }
}

@Inject
@User
Account userAccount;

public class AccountManager {
  @Produces
  @User
  Account userAccount = ...;
}