"Welcome To Ashok IT"				
			                       "Spring Boot and MicroServices"
                                                Topic : JavaBasedConfiguration
                                                Date  : 21/03/2024
                                                  (Session - 09)                               
_____________________________________________________________________________________________________________________________
Java Based Configuration Development
=====================================
* In addition to XML-based configuration, Spring also supports Java-based configuration and its new style of developing         Spring Application.

* It allows you to configure your Spring beans and dependencies using Java code. 

* Java-based configuration provides a more programmatic and type-safe approach compared to XML configuration. 

Steps for Developing Java Based Configuration Application
=========================================================

1) Enable Java-based configuration: 
===================================
* To enable Java-based configuration in your Spring application, you need to add the @Configuration annotation to a class.    

* This class will serve as your configuration class similarly to xml configuration file.

Example
=======
@Configuration
public class AppConfig {
    // Bean definitions and configuration methods
}

2) Define beans: 
================
* In your configuration class, you can define beans using the @Bean annotation on methods. 

* The return type of the method represents the type of the bean, and the method body contains the logic to create and   configure the bean.

Example
=======
@Configuration
public class AppConfig {
    
    @Bean
    public MyBean myBean() {
        return new MyBean();
    }
    
    @Bean
    public AnotherBean anotherBean() {
        return new AnotherBean();
    }
}

3) Main Program
===============
 * We can create the Main Program by Creating object of ApplicationContext with its implementation Class                  AnnotationConfigApplicationContext.

 * AnnotationConfigApplicationContext implementation class having capability to read the configurations from Java based          configuration class.

 * We need to provide the Configuration class to AnnotationConfigApplicationContext class.

Example
======
  public class MainClient{

     public static void main(String[] args){
        
           ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);

           //Requesting the Spring bean logic
     }

  }

Example Application on Java Based Configuration
===============================================
User.java
=========
package com.ashokit.beans;

public class User {
	
	private String username;
	
	private String password;

	//setter injection
	public void setUsername(String username) {
		this.username = username;
	}

	public void setPassword(String password) {
		this.password = password;
	}
	
	@Override
	public String toString() {
		return String.format("Username %s and password %s",username,password);
	}
}

Student.java
============
package com.ashokit.beans;

public class Student {
	
	//simple properties
	private String id;
	
	private String name;
	
	private String emailId;
	
	//Object
	private Course course;
	
	//setter injection
	public void setId(String id) {
		this.id = id;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
	public void setEmailId(String emailId) {
		this.emailId = emailId;
	}
	
	public void setCourse(Course course) {
		this.course = course;
	}
	
	@Override
	public String toString() {
		return String.format("StudentId %s and StudentName %s and EmailId %s and CourseName %s",id,name,emailId,course.getCourseName());
	}

}

Course.java
===========
package com.ashokit.beans;

public class Course {
	
	private String courseName;
	
	private Integer courseFee;	
	
	public void setCourseName(String courseName) {
		this.courseName = courseName;
	}
	
	public void setCourseFee(Integer courseFee) {
		this.courseFee = courseFee;
	}
	
	public String getCourseName() {
		return courseName;
	}
	
	public Integer getCourseFee() {
		return courseFee;
	}
	
	@Override
	public String toString() {
		return String.format("CourseName %s and CourseFee %s ", courseName,courseFee);
	}
}

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

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

import com.ashokit.beans.Course;
import com.ashokit.beans.Student;
import com.ashokit.beans.User;

//This will acts as Spring Configuration File
@Configuration
public class SpringConfig {
	
	//creating the Java method to represent as Spring bean i.e.,User
	@Bean
	public User getUserObject() {
		
		//return new User();
		User user = new User();
		user.setUsername("Mahesh");
		user.setPassword("Mahesh@123");
		return user;
	}
	
	//creating the Java method to represent as Spring bean i.e.,Address
	@Bean
	public Student getStudentObject() {
		Student st = new Student();
		st.setId("AIT123");
		st.setName("Mahesh");
		st.setEmailId("mahesh.ashokit@gmail.com");
		//Injecting the courseBean into student Bean
		st.setCourse(getCourseBean());
		return st;
	}
	
	@Bean
	public Course getCourseBean() {
		Course course = new Course();
		course.setCourseName("SpringBootMicroservices");
		course.setCourseFee(8000);
		return course;
	}
}


SpringClient.java
=================
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.ashokit.beans.Student;
import com.ashokit.beans.User;
import com.ashokit.config.SpringConfig;

public class SpringClient {
	
	public static void main(String[] args) {
		
		//creating the object for spring container and passing Java Based Configuration class
		ApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
		
		//Requesting the Spring beans
		User user = context.getBean(User.class);
		System.out.println(user.hashCode());
		User user1 = context.getBean(User.class);
		System.out.println(user1.hashCode());
		
		
		Student student = context.getBean(Student.class);
		System.out.println(student.hashCode());
		Student student1 = context.getBean(Student.class);
		System.out.println(student1.hashCode());
	}
}


OUTPUT
======
Username Mahesh and password Mahesh@123
StudentId AIT123 and StudentName Mahesh and EmailId mahesh.ashokit@gmail.com and CourseName SpringBootMicroservices

Inheriting configuration classes
================================
package com.ashokit.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;

import com.ashokit.beans.Course;
import com.ashokit.beans.Student;
import com.ashokit.beans.User;

//This will acts as Spring Configuration File
@Configuration
@Import(value = {DatabaseConfig.class,EmailConfig.class}) //Inheriting the configuration from DatabaseConfig class
public class SpringConfig {
	
	//creating the Java method to represent as Spring bean i.e.,User
	@Bean
	public User getUserObject() {
		
		//return new User();
		User user = new User();
		user.setUsername("Mahesh");
		user.setPassword("Mahesh@123");
		return user;
	}
	
	//creating the Java method to represent as Spring bean i.e.,Address
	@Bean
	public Student getStudentObject() {
		Student st = new Student();
		st.setId("AIT123");
		st.setName("Mahesh");
		st.setEmailId("mahesh.ashokit@gmail.com");
		//Injecting the courseBean into student Bean
		st.setCourse(getCourseBean());
		return st;
	}
	
	@Bean
	public Course getCourseBean() {
		Course course = new Course();
		course.setCourseName("SpringBootMicroservices");
		course.setCourseFee(8000);
		return course;
	}
}

NOTE
====
* @Import Annotation is used to import the spring bean definitions from another Spring Configuration classes.

* @ImportResource annotation is used to import the Spring bean definitions from XML file.

* @PropertySource is used to load the properties file into Spring container.

* @Value is used to extract the value from properties file based on supplied key.


SpringConfig.java
=================
package com.ashokit.spring.config;

import java.util.Date;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.ImportResource;
import org.springframework.context.annotation.PropertySource;

import com.ashokit.spring.beans.Demo;
import com.ashokit.spring.beans.User;

//Representating the Java class as spring configuration class
@Configuration

//Recognizing the Reading properties file by the spring container
@PropertySource(value = "applicationConfig.properties")

//Importing the one configuration class bean definition into another configuration class
@Import(value = {DatabaseConfig.class,EmailConfig.class})

//Importing the spring bean definitions from xml configuration file
@ImportResource(value = "spring.xml")

public class SpringConfig {
	
	//Reading property value from properties file
	@Value("${user.username}")
	private String username;
	
	@Value("${user.password}")
	private String password;

	//User class as spring Bean
	@Bean
	public User getUserObject() {
		User user = new User();
		user.setUsername(username);
		user.setPassword(password);
		return user;
	}
	
	@Bean
	public Demo getDemoObject() {		
		//return new Demo("Mahesh","Mahesh@123");
		return new Demo();
	}
	
	@Bean
	public Date getDateObject() {
		return new java.util.Date();
	}
}


applicationConfig.properties
============================
#Defining the some application specific configuration
user.username=Mahesh
user.password=Mahesh@12311111


spring.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"
	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">

		     <!-- Configuring the Address Bean -->
      <bean id="address1" class="com.ashokit.spring.beans.Address">
          <property name="doorNo" value="1-2-3"/>
          <property name="cityName" value="Chennai"/>
          <property name="pincode" value="12324"/>
     </bean>
</beans>


SpringClient.java
=================
package com.ashokit.spring.client;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.ashokit.spring.beans.Address;
import com.ashokit.spring.beans.Course;
import com.ashokit.spring.beans.Demo;
import com.ashokit.spring.beans.Student;
import com.ashokit.spring.beans.User;
import com.ashokit.spring.config.DatabaseConfig;
import com.ashokit.spring.config.EmailConfig;
import com.ashokit.spring.config.SpringConfig;

public class SpringClient {

	public static void main(String[] args) {
		
		//Creating container object and passing java based configuration class
		ApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
		
		//Request spring bean object based on object type
		User user = context.getBean(User.class);
		System.out.println(user);
		System.out.println(user.hashCode());
		User user1 = context.getBean(User.class);
		System.out.println(user1.hashCode());
		User user2 = context.getBean(User.class);
		System.out.println(user2.hashCode());
		
		Demo demo = context.getBean(Demo.class);
		System.out.println(demo);
		
		Student st = context.getBean(Student.class);
		System.out.println(st);
		
		Course ct = context.getBean(Course.class);
		System.out.println(ct);
		
		Address address = context.getBean(Address.class);
		System.out.println(address);
		
	}
}


Output
======
Student Class....
Course Class...
User [username=Mahesh, password=Mahesh@12311111]
1740223770
1740223770
1740223770
Demo [username=null, password=null]
com.ashokit.spring.beans.Student@1205bd62
com.ashokit.spring.beans.Course@7ef27d7f
Address [doorNo=1-2-3, cityName=Chennai, pincode=12324]