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					Date : 16-July-2024
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==========================
What is Spring Framework?
==========================

=> Java Based framework

=> It is free and open source

=> Loosely coupled

=> It is developed modular fashion

=> Spring first version released in 2004 (1.x)

=> The current version of spring is 6.x

=> Spring framework under license of VMWare

=> Below Modules in spring framework

1) Spring Core
2) Spring Context
3) Spring DAO
4) Spring ORM
5) Spring AOP
6) Spring Web MVC
7) Spring REST
8) Spring Security
9) Spring Cloud
10) Spring Batch
11) Spring Schedular...

============
Spring Core
============

=> Base module of spring framework

=> Providing fundamentals of spring

		1) IOC Container
		2) Dependency Injection
		3) Auto wiring

====================
Spring Context
====================

-> Provide support for configurations required for application

==============
Spring DAO
==============

=> DAO stands for Data Access Object

=> It is used to communicate with database

=> Spring DAO module providing predefined classes to simplify dao layer development.


java app ----> spring dao ----> jdbc ---> database

		Ex : jdbcTemplate.execute(sql);

===========
Spring ORM
===========

=> ORM stands for Object Relational Mapping

=> ORM is used to perform DB operations using objects.

		hibernate.save(empObj);

 java app ---> data jpa ---> orm -> hibernate --> jdbc -> db		

Note: Spring DAO & Spring ORM modules are used for database connectivity only

Spring DAO => represents data in text format

Spring ORM => represents data in objects format

===============
Spring Web MVC
===============

=> MVC means Model , View & Controller

=> This module is used to develop web applications

		Customer ----> application (C2B)

=> It supports for JSP and Thymeleaf as presentation technologies.

Note: JSP and Thymeleaf are outdated.

==============
Spring REST
==============

=> It is used to develop REST APIs (webservices)

=> REST API means distributed application.

=> If one application is communicating with another application then it is called as Distributed application.

	Ex: passport ----> aadhar

		gpay ---> bank app

================
Spring Security
================

=> It is used to implement security in our application

=> It provides below functionalities

		1) Authentication ( who can login ? )
		2) Authorization ( what they can access ?)

=============
Spring Cloud
=============

=> It provides resources to develop microservices based applications

Ex: Discovery server, api gateway, circuit breaker, config server....

==============
Spring Batch
==============

-> It is used to implement batch processing (bulk operation)

usecases:

1) Bank account stmt generation
2) Credit card bill generation
3) postpaid mobile bill generation

===========
Spring AOP
===========

=> AOP stands for Aspect oriented programming

=> It is used to seperate cross cutting logics from business logic.

cross cutting logics : security, tx, auditing, logging ...

==================
Spring Schedular
==================

=> It is used to schedule task execution.


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					Date : 17-July-2024
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===================
Spring Core module
===================

=> Base module of Spring Framework

=> Providing fundamentals of spring framework

		1) IOC
		2) DI
		3) Auowiring

=> Spring Core module is used to manage our classes in the project.		


=> In a project we will have several classes

		1) controller classes (req & resp)
		2) service classes (business logic)
		3) Dao classes (db communication)		

=> in project execution process, One java class should call another java class method

=> In 2 ways one java class can call another java class method

		1) Inheritance (IS-A)

		2) Composition (HAS-A)		

===============
IS-A Relation	
===============

=> Extend the properties from one class to another class

=> sub class can access super class method directley

		Engine - super class
		Car - sub class

Note: Car class can acces engine class method		

public class Engine {
	public int start() {
		// logic
		System.out.println("Engine started..");
		return 1;
	}
}

public class Engine {
	public int start() {
		// logic
		System.out.println("Engine started..");
		return 1;
	}
}	


=> In the above approach car is extending properties from Engine class.

=> In future car can't extend props from other classes bcz java doesn't support multiple inheritence.

=> To overcome problem of IS-A relation we can use HAS-A relation.

================
HAS-A relation
================

=> Create object and call the method

=> Inside car class create object for Engine class and call eng class method.


public class Car {

	public void drive() {

		Engine eng = new Engine();
		
		int engstatus = eng.start();
		if (engstatus == 1) {
			System.out.println("Journey started..");
		} else {
			System.out.println("Engine problem...");
		}
	}
}

=> If someone modify Engine class constructor then Car class will fail...

=> with IS-A and HAS-A relation our classes are becoming tightly coupled.

=> To overcome problems of IS-A and HAS-A relation we can use Spring Core module concepts.

		1) IOC Container
		2) Dependency Injection.

Dependency Injection : Create one class object and inject into another class object is called as Dependency Injection.	

IOC : Inversion of control

=> IOC is a principle which is used to manage & colloborate the classes available in our application.

=> IOC will perform Dependency Injection in our application.

=> By using IOC and DI we can achieve Loosely coupling among the classes.

=> We will give our java classes and configuration as input to IOC container.

Note: We can do configuration in 3 ways

		1) xml (outdated -> springboot will not support)

		2) java based

		3) Anntoations

=> IOC will take our normal java classes and it provides Spring Beans.

=====================
What is Spring Bean
=====================

The java class which is managed by IOC is called as Spring bean.

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								Date : 18-July-2024
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===============================================
First App development using Spring framework
===============================================

1) Create Maven Project
	
	- select simple project (standalone)
	- groupId : in.ashokit
	- artifactId : 01-Spring-App

2) Configure Spring Framework as a dependency in pom.xml

		URL : www.mvnrepository.com

-------------------------------------------
<dependencies>
	<dependency>
		<groupId>org.springframework</groupId>
		<artifactId>spring-context</artifactId>
		<version>6.1.11</version>
	</dependency>
</dependencies>
------------------------------------------

3) Create Java classes

4) Create Spring Bean Configuration file

	Location : src/main/resources/spring-beans.xml

--------------------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="eng" class="in.ashokit.Engine"/>
    
    <bean id="car" class="in.ashokit.Car"/>

</beans>
---------------------------------------------------------	

5) Create Test class to run the application.

public class Test {
	public static void main(String[] args) {

		// starting IOC by giving xml as input
		ApplicationContext ctxt = new ClassPathXmlApplicationContext("spring-beans.xml");

		Engine engine = ctxt.getBean(Engine.class);
		engine.start();
	}
}

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								Date : 19-July-2024
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-> creating one cls obj and inject into another clas obj is called as dependency injection.

1) What is depedency injection ?

2) How many ways we can perform dependency injection ?

3) What is constructor injection ?

4) What is setter injection >


-----------------

public class Car {

	private Engine eng; // default value is null

	public Car() {
		System.out.println("Car - Constructor...");
	}

	public void setEng(Engine eng) {
		System.out.println("setEng() - caled..");
		this.eng = eng;
	}

	public void drive() {
		int status = eng.start();
		if (status == 1) {
			System.out.println("journey started..");
		} else {
			System.out.println("engine problem..");
		}
	}

}

-------------------------------------

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">


	<bean id="e" class="in.ashokit.Engine" />

	<bean id="c" class="in.ashokit.Car">
		<property name="eng" ref="e" />
	</bean>

</beans>

--------------------------------------------------

public class Test {

	public static void main(String[] args) {

		ApplicationContext ctxt = new ClassPathXmlApplicationContext("spring-beans.xml");

		Car c = ctxt.getBean(Car.class);
		c.drive();

	}
}

-----------------------------------------------------

######################################################
			Date : 22-July-2024
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---------------------
Setter injection :
--------------------
inject dependent bean obj into target bean obj using target class setter method.

	ex: <property name="" ref=""/>

-------------------------
Constructor injection : 
-------------------------

Inject dependent bean obj into target bean obj using target class parameterized constructor.

	ex: <constructor-arg name="" ref=""/>

-----------------------------------------------------
Q) If perform both CI and SI then what will happen ?
-----------------------------------------------------

CI will happen at the time of obj creation

SI will happen after object creation

Hence SI will override CI value


----------------------------------

public class Printer {
	
	public Printer() {
		System.out.println("Printer - Constructor...");
	}
	
	public void print() {
		System.out.println("Receipt printing....");
	}

}

---------------------------------
public class ATM {

	private Printer printer;// null

	public ATM() {
		System.out.println("ATM : 0-param Constructor");
	}

	public ATM(Printer printer) {
		System.out.println("ATM : 1-param Constructor");
		this.printer = printer;
	}
	
	public void setPrinter(Printer printer) {
		System.out.println("setter - method called..F");
		this.printer = printer;
	}

	public void withdraw(int amt) {
		System.out.println("amt deducted...");
		printer.print();
	}

}
------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

	<bean id="p" class="in.ashokit.beans.Printer" />

	<bean id="atm" class="in.ashokit.beans.ATM">
		<property name="printer" ref="p" />
		<constructor-arg name="printer" ref="p" />
	</bean>

</beans>
--------------------------------------------------

public class Test {

	public static void main(String[] args) {

		ApplicationContext ctxt = 
				new ClassPathXmlApplicationContext("beans.xml");

		ATM bean = ctxt.getBean(ATM.class);
		bean.withdraw(1000);
	}

}

######################################################
			Date : 23-July-2024
######################################################

=> Please watch below videos before coming to next session

Debugging : https://youtu.be/2WxsClYhreE?si=E7X-0Qk4So4Ib65K

Eclipse Shortcuts : https://youtu.be/TvYMey5SYa8?si=YV0mo9XH1leym6j0

Self Introduction : https://youtu.be/xvSO8cIOmlE?si=2Q6svRaolvEY7yAU

Roles & responsibilities : https://youtu.be/72tbMvbXAq4?si=DUWDHLkt7cTSwj4r

Strings Coding Challenges: https://youtu.be/RMRkK3rF1OU?si=EKkyDz2j4SE7zO2R

######################################################
			Date : 24-July-2024
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1) Programming Languages Vs Technologies Vs Framework

2) What is Framework

3) Struts Vs Hibernate Vs Spring

4) Spring framework introduction

5) Spring Architecture

6) Spring Modules Overview

7) Spring Core Module

8) IOC & DI

9) Setter Injection (SI)

10) Constructor Injection (CI)