"Welcome To Ashok IT"				
			                         "Spring Boot and MicroServices"
                                                Topic : Spring Core - Component Scan
                                                  Date  : 22/03/2025
                                                    (Session - 10)                               
_____________________________________________________________________________________________________________________________
Yesterday Session
=================
* different annotations have been used for Java Based Configuration

  1) @configuration

  2) @Bean

  3) @Import

  4) @ImportResource

  5) @PropertySource
  
  6) @Value

  7) @Autowired

  8) @Qualifier

Today session : Component Scan
==============================
> Automatically IOC Container will recognize the Spring Beans from packages of Project

> In the Component Scan Feature as programmer we no need to configure any Java Class as Spring Bean in spring configuration     file (or) Java based configuration class

> To Activate the Component Scan feature for Spring Application for below tag.

     xml configuration        ----> <context:component-scan base-package="base package names"/>

     Java Based Configuration ----> @Componentscan

> To Make Java class as spring bean we need to use either any one of stero type annotations as below

      1) @Controller

      2) @Service
 
      3) @Repository

      4) @Component

* The above annotations are used in the application development according to layered component

     @Service    >> To Mark Java class as Spring Bean Class and it can be used for only Business classes.

     @Controller >> To Mark Java Class as Spring Bean class and it can be used for only Handling the Requests in                                   webapplication.

     @Repoistory >> To Mark Java Class as spring bean class and it can be used only for DAO Classes.
 
     @Component  >> To Mark Java Class as spring bean class and it can be used for both Helper and Utilities classes in                           Application.
+++++++
Example
+++++++
     com
      |-> ashokit
            |-> controller ------------------------------>We can have the classes which annotated @Controller Annotation
                    |-> *.java
            |-> services -------------------------------->We can have the classes which annotated @Service Annotation
                    |-> *.java
            |-> dao-------------------------------------->We can have the classes which annotated @Repoistory Annotation
                  |-> *.java
            |-> helper----------------------------------->We can have the classes which annotated @Component Annotation
                  |-> *.java
            |-> util------------------------------------->We can have the classes which annotated @Component Annotation
                  |-> *.java

 NOTE
 ====
 Here base package will be "com.ashokit" the IOC Container will scan the packages from this package and its sub packages as
 well.

Example Application
===================

UserController.java
===================
package com.ashokit.controller;

import org.springframework.stereotype.Controller;

@Controller
public class UserController {
	
	public UserController() {
		System.out.println("Constructor From UserController....");
	}
}

CustomerController.java
=======================
package com.ashokit.controller;

import org.springframework.stereotype.Controller;

@Controller
public class CustomerController {

	public CustomerController() {
		System.out.println("Constructor From CustomerController....");
	}
}

CustomerDaoImpl.java
====================
package com.ashokit.dao;

import org.springframework.stereotype.Repository;

@Repository
public class CustomerDaoImpl {

	public CustomerDaoImpl() {
		System.out.println("Constructor From CustomerDaoImpl....");
	}
}

UserDaoImpl.java
================
package com.ashokit.dao;

import org.springframework.stereotype.Repository;

@Repository
public class UserDaoImpl {

	public UserDaoImpl() {
		System.out.println("Constructor From UserDaoImpl....");
	}
}

CustomerHelper.java
===================
package com.ashokit.helper;

import org.springframework.stereotype.Component;

@Component
public class CustomerHelper {
	
	 public CustomerHelper() {
		System.out.println("Constructor From CustomerHelper....");
	}
}

UserHelper.java
================
package com.ashokit.helper;

import org.springframework.stereotype.Component;

@Component
public class UserHelper {
	
	public UserHelper() {
		System.out.println("Constructor From UserHelper");
	}

}

CustomerService.java
====================
package com.ashokit.service;

import org.springframework.stereotype.Service;

@Service
public class CustomerService {

	public CustomerService() {
		System.out.println("Constructor From Customer Service....");
	}
}

UserService.java
================
package com.ashokit.service;

import org.springframework.stereotype.Service;

@Service
public class UserService {
	
	public UserService() {
		System.out.println("Constrcutor from userservice....");
	}

}

DateUtils.java
==============
package com.ashokit.utils;

import org.springframework.stereotype.Component;

@Component
public class DateUtils {
	
	public DateUtils() {
		System.out.println("Constructor From DateUtils...");
	}

}

StringUtils.java
================
package com.ashokit.utils;

import org.springframework.stereotype.Component;

@Component
public class StringUtils {
	
	public StringUtils() {
		System.out.println("Constructor From StringUtils");
	}
}

spring.xml
==========
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       https://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       https://www.springframework.org/schema/context/spring-context.xsd">
       
       <!--Enabling the Component Scan Feature in Spring IOC-->
       <context:component-scan base-package="com.ashokit"/>
  
</beans>       

App.java
========
package com.ashokit;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.ashokit.controller.UserController;
import com.ashokit.dao.UserDaoImpl;
import com.ashokit.service.UserService;
import com.ashokit.utils.DateUtils;

public class App 
{
    public static void main( String[] args ){
    	
    	//Activate the Container
    	ApplicationContext context = new ClassPathXmlApplicationContext("com/ashokit/spring/config/spring.xml");
    	
    	UserController userController = context.getBean(UserController.class);
    	System.out.println(userController);
    	
    	UserService userService = context.getBean(UserService.class);
    	System.out.println(userService);
    	
    	UserDaoImpl UserDaoImpl = context.getBean(UserDaoImpl.class);
    	System.out.println(UserDaoImpl);
    	
    	DateUtils dateUtils = context.getBean(DateUtils.class);
    	System.out.println(dateUtils);
    	
    	/*String[] beanNames = context.getBeanDefinitionNames();
    	Arrays.stream(beanNames).forEach(beanName -> System.out.println(beanName));*/
    	
    }
}

ApplicationConfig.java
======================
package com.ashokit.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
//Enabling the component scan for java based configuration
@ComponentScan(basePackages = "com.ashokit")
public class ApplicationConfig {

}


OUTPUT
======
Constructor From CustomerController....
Constructor From UserController....
Constructor From CustomerDaoImpl....
Constructor From UserDaoImpl....
Constructor From CustomerHelper....
Constructor From UserHelper
Constructor From Customer Service....
Constrcutor from userservice....
Constructor From DateUtils...
Constructor From StringUtils
com.ashokit.controller.UserController@740cae06
com.ashokit.service.UserService@26d9b808
com.ashokit.dao.UserDaoImpl@f78a47e
com.ashokit.utils.DateUtils@644baf4a