Jakarta EE @ApplicationScoped Anotasyonu

Giriş

Eski kodlarda şu satırı dahil ederiz.

import javax.ejb.ApplicationScoped;

Şu satırı dahil ederiz

import jakarta.enterprise.context.ApplicationScoped;

Normalde Jakarta EE CDI ile herhangi bir anotasyon kullanmaya gerek yok. Açıklaması şöyle

The requirements for a CDI bean are very minimal: a default constructor, implicitly or explicitly defined, and a concrete class is all that is needed. There is no need to use any kind of annotation, to indicate it can be handled through the CDI subsystem.

Ancak bazen CDI bean'lerine kapsam (scope) vermek gerekir. Çünkü bunu yapmazsak, CDI bean her seferinden yeniden yaratılır. Açıklaması şöyle

Most of the time, an annotation is placed on the class to indicate when the bean can be disposed of, and how many copies of the bean can be created. In the absence of such an annotation, the bean is created every time an 'Injection' is requested and disposed of when the other class is disposed of.

Verilebilecek kapsam anotasyonları 3 tane. Açıklaması şöyle

@jakarta.enterprise.context.ApplicationScoped: one instance for the entire application.

@jakarta.enterprise.context.SessionScoped: an instance is typically linked with a user Session like the HTTP Session.

@jakarta.enterprise.context.RequestScoped: an instance for each user request.

Since the ApplicationScoped can't hold any user or request specific information, it is ideal for providing functionality to your application, also known as services.

SessionScoped is typical for holding user information (like logged in user) and RequestScoped can be used to keep information related to the specific user request. 

@Application anotasyonu state tutmayan singleton bir bean yaratır. Açıklaması şöyle

Since the ApplicationScoped can't hold any user or request specific information, it is ideal for providing functionality to your application, also known as services.

SessionScoped is typical for holding user information (like logged in user) and RequestScoped can be used to keep information related to the specific user request. 

Örnek

Şöyle yaparız

@ApplicationScoped
public class GreetingService {
  ...
}