1 Component v Prototype

• @Component annotation tells the class that it is used for DI injection. Note annotation is completely diff from decorator in python.
  • by default the class is a auto-initialized singleton, the Alien class will automatically get constructed and call it’s constructor "Alien constructed" only ONCE
  • @Scope(value="prototype") annotation means the class is not an auto-initialized singleton, and constructor behaves more like a regular object.

@Component
public class Alien {
    private int aid;
    private String aname;
    public Alien() {
        super();
        System.out.println("Alien constructed")
    }
    public int getAid() {
        return aid;
    }

@Component
@Scope(value="prototype")
public class Alien {
    private int aid;
    private String aname;
    public Alien() {
        super();
        System.out.println("Alien constructed")
    }

2 IOC

Bean is just a java class with private variable, getters and setters

• ConfigurableApplicationContext context is the IOC container.
  • context.getBean(Alien.class); indicates that context can build the Alien bean meaning context is a bean factory.

3 Proxy pattern

• A proxy wraps around all objects