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Spring Boot
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=> Spring Boot is an extension for existing spring framework.

=> SpringBoot is an approach to develop Spring Based applications with less configurations.

=> Spring Boot came into market in 2015 (SpringBoot 1.x version)

=> The current version of Spring Boot is 3.x

=> What type of projects we can build using spring, same type of projects we can build using springboot also with very less configuration.

Note: In spring framework programmers are responsible for configuration management. Those configurations are common in every project.

=> Spring Boot supports rapid application development.

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Advantages with Spring Boot
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1) POM starters

2) Auto configuration

3) Embedded Servers

4) Actuators

======================
What is POM Starter ?
======================

=> POM starters are used to simplify maven dependencies configuration in project pom.xml. We have several springboot starters like below

			a) spring-boot-starter

			b) spring-boot-starter-web

			c) spring-boot-starter-data-jpa

			d) spring-boot-starter-mail

			e) spring-boot-starter-security

			f) spring-boot-starter-actuator

Note: For all these starters we have a parent starter 'spring-boot-starter-parent'.	

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What is Auto Configuration ?
==============================

=> Auto Configuration is one of the most popular functionality in springboot.

=> It is used to identify what configuration required for the application and provide that configuration in the application runtime.	

Note: Auto Configuration works based on pom starters.


=> if we add 'web-starter' : It provides tomcat server for deployment

=> If we add 'security-starter' : It provides login page for authentication

=> If we add 'jpa-starter' : It provides DB connections

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What is Embedded Server ?
============================ 

=> Embedded Server nothing but in built server provided by springboot to run our application.

=> When we add 'web-starter' then springboot will provide tomcat server by default to run our web application.

Note: We no need to download and install external servers from now..

=> SpringBoot supports 3 Embedded Servers

		1) Tomcat (default)

		2) Jetty

		3) Netty

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What is Actuator ?
=====================

=> Actuators are used to monitor and manage our springboot application.

=> Using Actuators we can get below details

		1) how many beans loaded by our application

		2) how many url patterns available in our application

		3) What config props loaded by our application

		4) App Env Details

		5) Threads Details of our application

		6) Heap details of our application


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How to create SpringBoot application
=======================================

=> To create spring boot application, spring team provided 'spring intializr website'.

		Website URL : https://start.spring.io/

=> When we use intializr website we have to download project as zip file then extract it and import that project into our IDE (eclipse/intellij/STS).		

Note-1 : In Eclipse IDE we can't create Spring Boot Application directley.

Note-2 : In IntelliJ Community IDE we can't create Spring Boot application directly. IntelliJ Enterprise edition having direct support to create boot app.

Note-3 : Spring Team provided STS IDE to create Spring Boot application directley. STS IDE also internally uses 'start.spring.io' website to create the project.

		STS IDE URL : https://spring.io/tools


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What is start class in Spring Boot ?
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=> When we create springboot application by default one java class will be created that is called as Start class of spring Boot Application.

=> It is entry point for springboot application execution. Application execution starts from here only.

--------------------------------------------------------------------
@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}
}		
---------------------------------------------------------------------

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What is happening inside start class run ( ) method ?
=========================================================

=> run ( ) method contains bootstrapping(getting started) logic for springboot application.

=> Below logics are implemented inside run ( ) method

		1) create bootstrap context

		2) Run listeners

		3) prepareEnvironment

		4) print banner

		5) createApplicationContext (IOC)

		6) call Runners

		7) Return IOC container obj 

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What is @SpringBootApplication annotation?
============================================

=> This annotation is used at start class of the Spring Boot.

=> This one annotation is equal to below 3 annotations

		1) @SpringBootConfiguration

		2) @EnableAutoConfiguration

		3) @ComponentScan

Note: In springboot application, by default start-class package will be considered as base package for Component Scanning.		


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What is Banner ?
=================

=> Banner is a logo that is printing on the console when we start our Springboot application.

=> We can customize springboot banner by creating "banner.txt" file under "src/main/resources" folder.

=> Spring Boot Banner works on Modes. We have below 3 modes

			1) CONSOLE (default)

			2) LOG

			4) OFF

=> We can set banner mode like below in application.properties file

		spring.main.banner-mode=off

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What is Runner in Spring Boot ?	
=================================

=> If we have any requirement to the execute the logic only once when the spring boot application got started then we can use Runners in Spring Boot.

Ex:

Usecase-1 : Load static tables data into cache memory when app starts.

Usecase-2 : remove data from temp tables (staging tables) in our database when application starts.

Usecase-3 : Send an email when application got started.

=> We have 2 types of Runners in Springboot

		1) ApplicationRunner (FI)

		2) CommandlineRunner (FI)

-------------------------------------------------------------------------
@Component
public class MyAppRunner implements ApplicationRunner {

	@Override
	public void run(ApplicationArguments args) throws Exception {
		System.out.println("MyAppRunner - run() method called");
	}

}
-------------------------------------------------------------------------

Note: Our Runners will be called as part of SpringApplication.run ( ) method.		

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Summary
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1) Spring Vs SpringBoot

2) What is Spring Boot & Why

3) Spring Boot Advantages

4) What is POM Starter

5) What is Auto Configuration

6) What is Embedded Server

7) What is Actuator

8) What is start class in Spring Boot ?

9) What is happening inside SpringApplication.run ( ) method ?

10) What is @SpringBootApplication annotation ?

11) What is Banner in SpringBoot and how to customize ?

12) What is Runner in springboot & usecases


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By using Spring Boot with Spring Core concepts we have to develop applications

1) Web Applications

2) ReST APIs

3) Microservices