Spring Part 09 - @Bean

 Spring - @Bean

package com.ah.di;

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

@Configuration
@ComponentScan
public class AppConf {

    @Bean("car")
    public Car carBean(){
        Car car = new Car();
        return car;
    }
}

package com.ah.di;

import org.springframework.beans.factory.annotation.Autowired;

public class Car {

    @Autowired
    private Engine engine;

    public void displayCarInfo(){
        System.out.println("car class display method\n");

        if(engine==null){
            System.out.println("No engine object");
        }else{
            engine.testEngine();
        }
    }

}

package com.ah.di;

import org.springframework.stereotype.Component;

@Component
public class Engine {

    public void testEngine(){
        System.out.println("testEngine() method of 

Engine class")
    }
}

package com.ah.di;

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

public class Test {

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

(AppConf.class);

    var carObj = context.getBean("car",Car.class);
     carObj.displayCarInfo();

     //displyAppContextBeanInfo(context);
    }

    public static void displyAppContextBeanInfo(ApplicationContext context ){
         for(String bean : 

context.getBeanDefinitionNames()){
            System.out.println(bean);
        }
    }

}

                                                                   Watch Demo

Spring Part 08 - @ComponentScan & @Configuration

 Spring - @ComponentScan & @Configuration

In this Part of Spring Framework  we will avoid using Spring configuration xml file, instead we will maintain configuration at java side by using the '@Configuration' annotation.

package com.ah.di.samp;

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

@Configuration
@ComponentScan(basePackages = "com.ah.di")
public class AppConf {
}

package com.ah.di;

import org.springframework.stereotype.Component;

@Component
public class Car {

    public void displayCarInfo(){
        System.out.println("car class display method");
    }
}

package com.ah.di;

import com.ah.di.samp.AppConf;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.

AnnotationConfigApplicationContext;

public class Test {

    public static void main(String[] args) {

        ApplicationContext context =

    new AnnotationConfigApplicationContext

(AppConf.class);

    var carObj = context.getBean("car",Car.class);
     carObj.displayCarInfo();

     //displyAppContextBeanInfo(context);

    }

    public static void displyAppContextBeanInfo

(ApplicationContext context ){

         for(String bean : context.

getBeanDefinitionNames()){

            System.out.println(bean);

        }
    }
}

                                                                        Watch Demo

Spring Part 07 - @Component

  Spring - @Component

Maven Dependency:

<dependency>

  <groupId>org.springframework</groupId>

  <artifactId>spring-context</artifactId>

  <version>5.3.16</version>

</dependency>

Sample Program for @Component using 'Spring Framework' 

beans_di.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">

<context:component-scan base-package="com.ah.di"/>

</beans>

<context:component-scan base-package="com.ah.di"/>

package com.ah.di;



import org.springframework.context.ApplicationContext;

import org.springframework.context.support.

ClassPathXmlApplicationContext;



public class Test {

    public static void main(String[] args) {

        ApplicationContext context =

    new ClassPathXmlApplicationContext("beans_di.xml");

        /*for(String bean : 

context.getBeanDefinitionNames()){

            System.out.println(bean);

        }*/
       
        var carObj = context.getBean("car",Car.class);
         carObj.displayCarInfo();
    }
}

package com.ah.di;

import org.springframework.stereotype.Component;

@Component
public class Car {

    public void displayCarInfo(){
        System.out.println("car class display method

");
    }
}

package com.ah.di;

import org.springframework.stereotype.Component;

@Component
public class Engine {

    public void testEngine(){
        System.out.println("Engine is working");
    }
}

                                                                      Watch Demo

Spring Part 06 - @Qualifier

  Spring - Qualifier

Maven Dependency:

<dependency>

  <groupId>org.springframework</groupId>

  <artifactId>spring-context</artifactId>

  <version>5.3.16</version>

</dependency>

Sample Program for @Qualifier using 'Spring Framework' 

beans_di.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">

    <context:annotation-config/>

    <bean id="engineModel1" class="com.ah.di.Engine">
        <property name="engineModel" value="Model-1"/>
    </bean>

    <bean id="engineModel2" class="com.ah.di.Engine">
        <property name="engineModel" value="Model-2"/>
    </bean>

    <bean id="car" class="com.ah.di.Car" />

</beans>

package com.ah.di;

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

public class Test {

    public static void main(String[] args) {

        ApplicationContext context =

                new ClassPathXmlApplicationContext("beans_di.xml");

        Car car = context.getBean("car",Car.class);
        car.checkCarEngine();
    }

}

package com.ah.di;

import org.springframework.beans.factory.annotation.Autowired
import or.springframework.beans.factory.annotation.Qualifier;

public class Car {

    @Autowired
    @Qualifier("engineModel2")
    private Engine engine;

    public void checkCarEngine(){
        if(engine!=null){
            engine.testEngine();
        }else{
            System.out.println("Engine is dead");
        }
    }
}

package com.ah.di;

public class Engine {

    public void testEngine(){
        System.out.println("engine is working" );
    }
}

                                                                           Watch Demo

Spring Part 05 - Autowiring

Spring - Autowiring

Maven Dependency:

<dependency>

  <groupId>org.springframework</groupId>

  <artifactId>spring-context</artifactId>

  <version>5.3.16</version>

</dependency>

Sample Program for Autowiring using 'Spring Framework' 

beans_di.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
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="engineObj" class="com.ah.di.Engine"/>

    <bean id="car" class="com.ah.di.Car" autowire="byType"/>

</beans>

package com.ah.di;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

    public static void main(String[] args) {

        ApplicationContext context =

                new ClassPathXmlApplicationContext("beans_di.xml");

        Car car = context.getBean("car",Car.class);

        car.checkCarEngine();

    }

}

package com.ah.di;

public class Car {

    private Engine engine;

    public void setEngine(Engine engine) {
        this.engine = engine;
    }

    public void checkCarEngine(){

        if(engine!=null){
            engine.testEngine();
        }else{
            System.out.println("Engine is dead");
        }

    }

}

package com.ah.di;

public class Engine {

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

    public void testEngine(){
        System.out.println("engine is working" );
    }

}

beans_di.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">

    <context:annotation-config/>

    <bean id="engine" class="com.ah.di.Engine">
        <property name="engineModel" value="Model-1"/>
    </bean>

    <bean id="carBattery" class="com.ah.di.Battery"/>

    <bean id="car" class="com.ah.di.Car" />

</beans>

package com.ah.di;

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

public class Test {

    public static void main(String[] args) {
        ApplicationContext context =
                new ClassPathXmlApplicationContext("beans_di.xml");

        Car car = context.getBean("car",Car.class);
        car.checkCarEngine();
    }
}

package com.ah.di;

import org.springframework.beans.factory.annotation.Autowired;

public class Car {

    @Autowired
    private Engine engine;

    @Autowired
    private Battery battery;

    public void checkCarEngine(){
        if(engine!=null){
            engine.testEngine();
        }else{
            System.out.println("Engine is dead");
        }

        if(battery!=null){
            battery.displayBatteryStatus();
        }else{
            System.out.println("Battery is dead");
        }
    }

}

package com.ah.di;

public class Engine {

    private String engineModel;

    public void setEngineModel(String engineModel) {
        this.engineModel = engineModel;
    }

    public void testEngine(){
        System.out.println("engine is working" );
        System.out.println("engineModel :: "+engineModel );
    }

}

                                                                 Watch Demo

Spring Part 04 - Setter Injection (Class)

Spring - Dependency Injection

Dependency Injection using class

Sample Program for Dependency Injection using 'Spring Framework'

beans_di.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
        https://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="car" class="com.ah.di.Car">
        <property name="engine">
            <bean class="com.ah.di.Engine"/>
        </property>
    </bean>

</beans>

package com.ah.di;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

    public static void main(String[] args) {

        ApplicationContext context = new ClassPathXmlApplicationContext("beans_di.xml");

        Car car = context.getBean("car",Car.class);

        car.checkCarEngine();

    }

}

package com.ah.di;



public class Car {

    private Engine engine;



    public void setEngine(Engine engine) {

        this.engine = engine;

    }

    public void checkCarEngine(){

        if(engine!=null){

            engine.testEngine();

        }else{

            System.out.println("Engine is dead");

        }

    }

}

package com.ah.di;

public class Engine {

    public void testEngine(){

        System.out.println("engine is working" );

    }

}

                                                                         Watch Demo