[JAVA] Spring Bean 사용하기

 

 

Spring 세팅

• maven project 생성
• pom.xml 에 dependency 추가 : https://mvnrepository.com/

 

 

Context.xml 에 Bean 태그 사용해서 객체 생성하기

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context"
	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 
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

	<!-- 
		@Bean
		Fuel makeFuel(){
			return new Water();
			}	
	-->
    
	<bean id="makeFuel" class="Pack01.Water"/>
    
	<bean id="makeGas" class="Pack01.Gas"/>
    
	<!-- 
		@Bean
		Airplane makeAirplane() {
		return new Airplane(makeFuel());
		}
	 -->
     
	<bean id="makeAirplane" class="Pack01.Airplane">
		<constructor-arg ref="makeFuel"/>
	</bean>
	<bean id="makeShip" class="Pack01.Ship">
		<constructor-arg ref="makeGas"/>
	</bean>
	<bean id="makeCar" class="Pack01.Car">
		<constructor-arg ref="makeGas"/>
	</bean>
		 
</beans>

• @Bean : 함수/객체 호출 자체를 Spring 이 하도록 하는 어노테이션
• bean 태그의 id : 만들 함수의 이름
• bean 태그의 class : 함수에서 리턴할 값 정의
• constructor-arg 태그의 ref : 생성자의 인수 전달을 위한 태그

 

 

 

Hello.java 작성 

 

Factory Pattern 사용

package Pack01;
import org.springframework.context.support.GenericXmlApplicationContext;

interface Fuel{
	String getFuel();
}

class Water implements Fuel{
	public String getFuel() {
		return "물";
	}
}

class Gas implements Fuel{
	public String getFuel() {
		return "가스";
	}
}

class Airplane{
	Fuel fuel;
	Airplane(Fuel fuel) { this.fuel = fuel; }
	void fly() {
		System.out.println(fuel.getFuel()+"로 날다.");
	}
}

class Ship{
	Fuel fuel;
	Ship(Fuel fuel) { this.fuel = fuel; }
	void fly() {
		System.out.println(fuel.getFuel()+"로 날다.");
	}
}

class Car{
	Fuel fuel;
	Car(Fuel fuel) { this.fuel = fuel; }
	void fly() {
		System.out.println(fuel.getFuel()+"로 날다.");
	}
}

@Configuration
// Factory 패턴
class Factory{
	@Bean
	Fuel makeFuel() {
		return new Water();
	}
	@Bean
	Airplane makeAirplane() {
		return new Airplane(makeFuel());
	}

	Ship makeShip() {
		return new Ship(makeFuel());
	}

	Car makeCar() {
		return new Car(makeFuel());
	}

}

public class Hello {
	public static void main(String[] args) {
		GenericXmlApplicationContext ctx = new GenericXmlApplicationContext("Context.xml");
		Airplane airplane = ctx.getBean("makeAirplane", Airplane.class);
		airplane.fly();
		Ship ship = ctx.getBean("makeShip", Ship.class);
		ship.fly();
		Car car = ctx.getBean("makeCar", Car.class);
		car.fly();
		}
}

 

Bean 객체 사용

package Pack01;
import org.springframework.context.support.GenericXmlApplicationContext;

interface Fuel{
	String getFuel();
}

class Water implements Fuel{
	public String getFuel() {
		return "물";
	}
}

class Gas implements Fuel{
	public String getFuel() {
		return "가스";
	}
}

class Airplane{
	Fuel fuel;
	Airplane(Fuel fuel) { this.fuel = fuel; }
	void fly() {
		System.out.println(fuel.getFuel()+"로 날다.");
	}
}

class Ship{
	Fuel fuel;
	Ship(Fuel fuel) { this.fuel = fuel; }
	void fly() {
		System.out.println(fuel.getFuel()+"로 날다.");
	}
}

class Car{
	Fuel fuel;
	Car(Fuel fuel) { this.fuel = fuel; }
	void fly() {
		System.out.println(fuel.getFuel()+"로 날다.");
	}
}

public class Hello {
	public static void main(String[] args) {
		GenericXmlApplicationContext ctx = new GenericXmlApplicationContext("Context.xml");
		Airplane airplane = ctx.getBean("makeAirplane", Airplane.class);
		airplane.fly();
		Ship ship = ctx.getBean("makeShip", Ship.class);
		ship.fly();
		Car car = ctx.getBean("makeCar", Car.class);
		car.fly();
		}
}

• Factory 패턴 사용하다가 bean 객체 사용하는 방식으로 변환
• GenericXmlApplicationContext : xml 업로드를 위한 클래스
• getBean("만든 bean 이름", 리턴 객체);

 

 

Factory 패턴이 무엇인지는 다음 포스팅에서 다룰 예정!!