What is an injection point?

An injection point is identified by the @Inject annotation. Previously, we covered a nondefault constructor for a bean that was annotated with @Inject, as shown in the following code:

public class PaymentProcessor {
  private final Payment payment;

  @Inject
  public PaymentProcessor(Payment payment) {
    this.payment = payment;
  }
}

This is known as bean constructor parameter injection and there can only be one constructor annotated with @Inject in a bean.

If a single constructor that defines every bean that we need to use, and thus needs to be injected, is not favored, there are two other ways to inject into our bean:

The major advantage of field over method injection is that it doesn't require any getter or setter methods to be present on the bean to perform the injection.

The first time that a bean is instantiated by the container is the point when beans that match the injection points are injected ready for use.

The order in which a bean is constructed by the container is as follows:

There are three types of injection points that don't require the presence of @Inject: producer, observer, and disposer methods.

@Produces
PaymentProcessor createProcessor(Payment payment) {
  return new PaymentProcessor(payment);
}

We'll cover observer methods as part of Chapter 7, Events.