When and how are beans initialized

Depending on the scope of your @Bean you will have a different behavior in terms of initialization, you can take as default like below:

Escope	Behavior
Singleton	Instance created and initialized during the startup of the application
Prototype	Lazily created every time the bean is requested.
Session	Lazily created once a new http session is created and bean requested
Request	Lazily created once a new http request is created and bean requested
WebSocket	Lazily created once a new web socket is created and bean requested

In case you want to change the default behavior you can do it with the annotation @Lazy or you can also do it in a more general way using the attribute lazyInit from @ComponentScan

As an example you could do like below

    
 @Component
 @Lazy(true)
 public class MySingletonClass {
    
    public MySingletonClass(){
        System.out.println("Lazy creation");
    }
        
 }