IOC and Dependency Injection

• you don't need to create an object for your java class.
• Spring IOC container will automatically create object and inject the dependent values.
• So, here spring is controlling our object creation i.e The control of object creation is not our hands.
• Service Locator Design Pattern.
• Bean Factory and Application Context

Spring Bean LifeCycle

• There are 2 important methods in the bean life cycle

a) init() b) destroy()

• The annotations used are @PostConstruct and @PreDestroy
• Code Explaining these methods:

    public class MyBean {
  
   @PostConstruct
   public void init() {
   // This method will be called after the bean is constructed and its properties are set.
   System.out.println("Bean initialization method called (init()).");
   }
  
   @PreDestroy
   public void destroy() {
   // This method will be called when the bean is being destroyed, typically during application shutdown.
   System.out.println("Bean destruction method called (destroy()).");
   }
  
   // Other methods and properties of the bean go here...
   }
  

Spring Scopes

• In Spring, the scope of a bean defines the lifecycle and visibility of the bean within the application context.
• There are 6 types

a) Singleton Scope

• This is the default scope in Spring.
• Only one instance of the bean is created per Spring container.
• The same instance is returned whenever the bean is requested.
• All subsequent requests for the bean will receive the same object reference.
• It's suitable for stateless beans or beans that share the same state across the application.

b) Prototype Scope

• A new instance of the bean is created each time it is requested.
• It means that the Spring container doesn't manage the lifecycle of the bean, and you are responsible for managing resources and cleanup if needed.
• Prototype-scoped beans are useful when you want a new instance of the bean every time it is injected or looked up.

c) Request Scope

• A new instance of the bean is created for each HTTP request.
• It is specific to web applications that use Spring's DispatcherServlet.
• Each user request receives a separate instance of the bean, isolated from other requests.
• Request-scoped beans are ideal for situations where you need data isolation per user request.

d) Session Scope

• A new instance of the bean is created for each user session.
• It is specific to web applications, and a user session can span multiple HTTP requests.
• Each user session maintains a separate instance of the bean.
• Session-scoped beans are useful when you want to store stateful data specific to a user's session.

e) Global Session Scope

• This scope is similar to the session scope, but it is specific to portlet-based web applications.
• It represents a global session that can span multiple portlets.
• Global session-scoped beans are used when you need data shared across multiple portlets within the same session.

f) Application Scope

• The bean instance is shared across the entire application context.
• It is specific to web applications, and the bean instance is created once for the entire application.
• Application-scoped beans are suitable for data that needs to be shared across multiple parts of the application.