비트 컴퓨터 [Spring] - ②

1. 객체 생성 방식

참고, 참고1, 참고2

1. DI (Dependency Injection, 의존 주입)

• 외부에서 두 객체 간의 관계를 결정해주는 디자인 패턴으로, 인터페이스를 사이에 둬서 클래스 레벨에서는 의존관계가 고정되지 않도록 하고 런타임 시에 관계를 다이나믹하게 주입하여 유연성을 확보하고 결합도를 낮출 수 있게 해준다.

2. AOP (Aspect Oriented Programming, 관점 지향 프로그래밍)

• 기능별로 class를 분리했음에도 불구하고 생기는 중복코드의 단점을 해결하고자 나온 방식, 공통기능과 핵심부분을 분리하여, 필요할 때에만 공통기능을 핵심부위에 넣어주는 방식

3. IoC (Inversion of Control,제어의 역전)

• 제어의 역전은 의존성 주입의 상위 개념

• 스프링 컨테이너가 필요에 따라 개발자 대신 Bean들을 관리(제어)해주는 행위

TDD (Test Driven Development, 테스트 주도 개발)

• 테스트 프로그램을 만드는 것
  • 코드는 볼 수 없다
  • 즉 프로그래머와 테스터는 분리된다.
    

2. DI (Dependency Injection, 의존 주입)

참조

• 주입 방식

  1. 생성자 주입

  2. 필드 주입 (@Autowired)

  3. setter 주입

  4. setter @Autowired 주입

스프링 X - 생성자 주입

//1. 스프링 없이 주입시키는 방법
// - 생성자 주입
class Apple{
	void f1() { System.out.println("test");  }
}

class Orange{
	
	Apple apple;
	
	Orange(Apple apple){
		this.apple = apple;
	}
	
	void f2() {
		apple.f1();
	}
}


public class Hello {

	public static void main(String[] args) {
		Orange orange = new Orange(new Apple());
		orange.f2();
		
	}

}

스프링 X - setter 주입

//2. 스프링 없이 주입시키는 방법
//- setter 주입
class Apple{
	void f1() { System.out.println("test");  }
}

class Orange{
	
	Apple apple;
	void setApple(Apple apple) {
		this.apple = apple;
	}
	
	void f2() {
		apple.f1();
	}
}
public class Hello {

	public static void main(String[] args) {
		Orange orange = new Orange();
		orange.setApple(new Apple());
		orange.f2();
		
	}

}

ex1) 생성자 주입①

package Pack;

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

class Apple{
	void f1() {
		System.out.println("test");

	}
}

class Orange{
	Apple apple;
	Orange(Apple apple){
		this.apple = apple;
	}
	void f2() {
		apple.f1();
	}
}


@Configuration
class AppConfig{
	//Bean객체의 이름을 변경할 수 있다
	//@Bean(name="appleMange")
	@Bean
	Apple apple() {
		return new Apple();
	}
	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);
		//얘네들이 관리하는 객체의 수
		System.out.println(ctx.getBeanDefinitionCount());
		Orange orange = new Orange(new Apple());
		orange.f2();
		ctx.close();
		
	}

}

ex2) 생성자 주입②

package Pack;

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

class Apple{
	void f1() {
		System.out.println("test");

	}
}

class Orange{
	Apple apple;
    //생성자 주입
	Orange(Apple apple){
		this.apple = apple;
	}
	void f2() {
		apple.f1();
	}
}


@Configuration
class AppConfig{
	//Bean객체의 이름을 변경할 수 있다
	//@Bean(name="appleMange")
	@Bean
	Apple apple() {
		return new Apple();
	}
	
	//결국 apple은 싱글톤으로 같은 객체이다
	@Bean
	Orange orange() {
		return new Orange(apple());
	}
	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);
//		//얘네들이 관리하는 객체의 수
//		System.out.println(ctx.getBeanDefinitionCount());
//		Orange orange = new Orange(new Apple());
//		orange.f2();
//		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

ex3) 필드 주입 - @Autowired

1. 사용하지 말라고 권장된다. - 스프링 제작진
   • 서로 호출하면서 의존관계에 빠진다라는 주장
   • 하지만 어차피 처음부터 이렇게 짜면 안된다.
2. 실전에서 사용을 많이 한다.

package Pack;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

class Apple{
	void f1() {
		System.out.println("test");

	}
}

class Orange{
	@Autowired //아래와 동일한 생성자코드를 만들어준다. + 아래의 Orange(apple())
	Apple apple;
//	Orange(Apple apple){
//		this.apple = apple;
//	}
	
	
	void f2() {
		apple.f1();
	}
}


@Configuration
class AppConfig{
	//Bean객체의 이름을 변경할 수 있다
	//@Bean(name="appleMange")
	@Bean
	Apple apple() {
		return new Apple();
	}
	
	//결국 apple은 싱글톤으로 같은 객체이다
	@Bean
	Orange orange() {
		return new Orange();
	}
	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);
//		//얘네들이 관리하는 객체의 수
//		System.out.println(ctx.getBeanDefinitionCount());
//		Orange orange = new Orange(new Apple());
//		orange.f2();
//		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

ex4) setter 주입 (수정자 주입)

객체 수가 많을 때는 보이기 위해 주로 setter함수를 사용

• 객체가 적으면 생성자 주입을 주로 사용

package Pack;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

class Apple{
	void f1() {
		System.out.println("test");

	}
}

class Orange{
	
	Apple apple;
	
	//setter 주입 - 수정자 주입
	void setApple(Apple apple) {
		this.apple = apple;
	}
	
	void f2() {
		apple.f1();
	}
}


@Configuration
class AppConfig{

	@Bean
	Apple apple() {
		return new Apple();
	}
	
//	//결국 apple은 싱글톤으로 같은 객체이다
//	@Bean
//	Orange orange() {
//		return new Orange();
//	}
	

	//spring용 setter 주입
	@Bean
	Orange orange() {
		Orange o = new Orange();
		o.setApple(apple());
		return o;
	}

	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

//		//setter 주입
//		Orange o = new Orange();
//		o.setApple(new Apple());
//		o.f2();
		
		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

ex5) setter 주입 (수정자 주입) - @Autowired

package Pack;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

class Apple{
	void f1() {
		System.out.println("test");

	}
}

class Orange{
	
	Apple apple;
	
	//setter 주입 - 수정자 주입
	@Autowired
	void setApple(Apple apple) {
		this.apple = apple;
	}
	
	void f2() {
		apple.f1();
	}
}


@Configuration
class AppConfig{

	@Bean
	Apple apple() {
		return new Apple();
	}
	
//	//결국 apple은 싱글톤으로 같은 객체이다
//	@Bean
//	Orange orange() {
//		return new Orange();
//	}
	

	//spring용 setter 주입
	@Bean
	Orange orange() {
//		Orange o = new Orange();
//		o.setApple(apple());
//		return o;
		
		//@Autowired 사용할 시 이렇게만
		return new Orange();
	}

	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

//		//setter 주입
//		Orange o = new Orange();
//		o.setApple(new Apple());
//		o.f2();
		
		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

불변의 원칙

• 생성자 주입

package Pack;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

class Apple{
	void f1() {
		System.out.println("test");

	}
}

class Orange{
	//한번만 받도록
	//한 번 주입이 일어나면 이후는 불변의 원칙
	final Apple apple;
	
	Orange(Apple apple){
		this.apple = apple;
	}
	void f2() {
		apple.f1();
	}
}


@Configuration
class AppConfig{

	@Bean
	Apple apple() {
		return new Apple();
	}

	

	//spring용 setter 주입
	@Bean
	Orange orange() {
		return new Orange(apple());
	}

	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

@Nullable

• 객체가 없을 때, @Nullable은 setter 함수 호출은 시켜준 다음 터진다.

  • 따라서 제어코드 작성이 가능해진다.

package Pack;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;


class Apple{
	void f1() {
		System.out.println("----헤드라인----");

	}
}

class Orange{
    Apple apple;
    
    @Autowired
	//void setApple(Apple apple) {
    
    //Apple 객체가 없을 때, @Nullable은 호출은 시켜준다음 터진다
    void setApple(@Nullable Apple apple) {   
    	System.out.println("호출");
    	//@Nullable이 있기에 제어코드 작성이 가능해진다.
    	if(apple != null) {
    		this.apple = apple;
    	}
		
	}
	
	void f2() {
		if(apple != null) {
			apple.f1();
    	}
		System.out.println("대선 D-1");
		
	}
}


@Configuration
class AppConfig{

//	@Bean
//	Apple apple() {
//		return new Apple();
//	}

	//spring용 setter 주입
	@Bean
	Orange orange() {
		return new Orange();
	}

	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

• 객체가 있는 경우

package Pack;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;


class Apple{
	void f1() {
		System.out.println("----헤드라인----");

	}
}

class Orange{
    Apple apple;
    
    @Autowired
	//void setApple(Apple apple) {
    
    //Apple 객체가 없을 때, @Nullable은 호출은 시켜준다음 터진다
    void setApple(@Nullable Apple apple) {   
    	System.out.println("호출");
    	//@Nullable이 있기에 제어코드 작성이 가능해진다.
    	if(apple != null) {
    		this.apple = apple;
    	}
		
	}
	
	void f2() {
		if(apple != null) {
			apple.f1();
    	}
		System.out.println("대선 D-1");
		
	}
}


@Configuration
class AppConfig{

	@Bean
	Apple apple() {
		return new Apple();
	}

	//spring용 setter 주입
	@Bean
	Orange orange() {
		return new Orange();
	}

	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

Optional

• 객체가 있는지 없는지를 물어 사용하는 방법

• 객체 존재 X

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;


class Apple{
	void f1() {
		System.out.println("----헤드라인----");

	}
}

class Orange{
    Apple apple;
    
    @Autowired
	//void setApple(Apple apple) {
    
    //Apple 객체가 없을 때, @Nullable은 호출은 시켜준다음 터진다
    //void setApple(@Nullable Apple apple) {   
   	void setApple(Optional<Apple> apple) {   

    	if(apple.isPresent()) {
    		System.out.println("객체가 존재하는 경우");
    		this.apple = apple.get();
    	}else {
    		System.out.println("객체가 존재하지 않는 경우");
    		
    	}
    	System.out.println("호랑이");
		
	}
	
	void f2() {
		if(apple != null) {
			apple.f1();
    	}
		System.out.println("대선 D-1");
		
	}
}


@Configuration
class AppConfig{

//	@Bean
//	Apple apple() {
//		return new Apple();
//	}

	//spring용 setter 주입
	@Bean
	Orange orange() {
		return new Orange();
	}

	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

• 객체 존재 X

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;


class Apple{
	void f1() {
		System.out.println("----헤드라인----");

	}
}

class Orange{
    Apple apple;
    
    @Autowired
	//void setApple(Apple apple) {
    
    //Apple 객체가 없을 때, @Nullable은 호출은 시켜준다음 터진다
    //void setApple(@Nullable Apple apple) {   
   	void setApple(Optional<Apple> apple) {   

    	if(apple.isPresent()) {
    		System.out.println("객체가 존재하는 경우");
    		this.apple = apple.get();
    	}else {
    		System.out.println("객체가 존재하지 않는 경우");
    		
    	}
    	System.out.println("호랑이");
		
	}
	
	void f2() {
		if(apple != null) {
			apple.f1();
    	}
		System.out.println("대선 D-1");
		
	}
}


@Configuration
class AppConfig{

	@Bean
	Apple apple() {
		return new Apple();
	}

	//spring용 setter 주입
	@Bean
	Orange orange() {
		return new Orange();
	}

	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

문제가 발생하는 경우 - @Autowired

• 객체 생성자가 2개가 있는 경우

  • 싱글톤에서는 문제가 발생하지 않는다.

  • 하지만, AutoWired 잡으면 누구를 적용시켜야할지 모른다.

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;


class Apple{
	void f1() {
		System.out.println("----헤드라인----");

	}
}

class Orange{
    @Autowired
	Apple apple;

	void f2() {
		if(apple != null) {
			apple.f1();
    	}
		System.out.println("대선 D-1");
		
	}
}


@Configuration
class AppConfig{

	@Bean
	Apple apple01() {
		return new Apple();
	}
	

	@Bean
	Apple apple02() {
		return new Apple();
	}

	//spring용 setter 주입
	@Bean
	Orange orange() {
		return new Orange();
	}

	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

@Qualifier

• 한정자: 사용 범위를 조건이나 제한을 걸 때 사용되는 예약어

  • Default 값이기 때문에 생략이 가능하다

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;


class Apple{
	void f1() {
		System.out.println("----헤드라인----");

	}
}

class Orange{
    @Autowired
	Apple apple;

	void f2() {
		if(apple != null) {
			apple.f1();
    	}
		System.out.println("대선 D-1");
		
	}
}


@Configuration
class AppConfig{

	@Bean
	@Qualifier("apple01")
	Apple apple01() {
		return new Apple();
	}
	

	@Bean
	@Qualifier("apple02")
	Apple apple02() {
		return new Apple();
	}

	//spring용 setter 주입
	@Bean
	Orange orange() {
		return new Orange();
	}

	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		
		Orange orange = ctx.getBean("orange", Orange.class);
		orange.f2();
		
		ctx.close();
		
	}

}

• 상속에서의 Qualifier

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;


class Apple{
	void f1() {
		System.out.println("사과");

	}
}



class Orange extends Apple{
    
	@Override
	void f1() {
		System.out.println("오렌지");

	}
}

class Kiwi{
	Apple a1 = new Apple();
	Apple a2 = new Orange();
	@Autowired
	
	Apple apple; //Apple //Orange
	
	void f2() {
		apple.f1();
	}

}


@Configuration
class AppConfig{

	@Bean
	Apple apple() {
		return new Apple();
	}
	

	@Bean
	Orange orange() {
		return new Orange();
	}
	
	@Bean
	Kiwi kiwi() {
		return new Kiwi();
	}
	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		
		Kiwi kiwi = ctx.getBean("kiwi", Kiwi.class);
		kiwi.f2();
		
		ctx.close();
		
	}

}

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;


class Apple{
	void f1() {
		System.out.println("사과");

	}
}



class Orange extends Apple{
    
	@Override
	void f1() {
		System.out.println("오렌지");

	}
}

class Kiwi{
	Apple a1 = new Apple();
	Apple a2 = new Orange();
	@Autowired
	@Qualifier("orange")
	Apple apple; //Apple //Orange
	
	void f2() {
		apple.f1();
	}

}


@Configuration
class AppConfig{

	@Bean
	Apple apple() {
		return new Apple();
	}
	

	@Bean
	Orange orange() {
		return new Orange();
	}
	
	@Bean
	Kiwi kiwi() {
		return new Kiwi();
	}
	
}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		
		Kiwi kiwi = ctx.getBean("kiwi", Kiwi.class);
		kiwi.f2();
		
		ctx.close();
		
	}

}

예제

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;

//의존 관계 (Airplane-Water)
class Airplane{
	Water water;
	Airplane(Water water){
		this.water = water;
	}
	
	void fly() {
		this.water.use();
		System.out.print(" 날아간다.");
	}
	
}


class Water{
	void use() {
		System.out.print("물을 사용해서");
		
	}
}

@Configuration
class AppConfig{


}

public class Hello {

	public static void main(String[] args) {
		
		Airplane airplane = new Airplane(new Water());
		airplane.fly();

		
	}

}

• 스프링 연결

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;

//의존 관계 (Airplane-Water)
class Airplane{
	Water water;
	Airplane(Water water){
		this.water = water;
	}
	
	void fly() {
		this.water.use();
		System.out.print(" 날아간다.");
	}
	
}


class Water{
	void use() {
		System.out.print("물을 사용해서");
		
	}
}

@Configuration
class AppConfig{
	@Bean
	Water water() {
		return new Water();
	}

}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		Water water = ctx.getBean("water", Water.class);
		Airplane airplane = new Airplane(water);
		airplane.fly();
		ctx.close();
		
	}

}

• 자동 생성

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;

//의존 관계 (Airplane-Water)
class Airplane{
	Water water;
	Airplane(Water water){
		this.water = water;
	}
	
	void fly() {
		this.water.use();
		System.out.print(" 날아간다.");
	}
	
}


class Water{
	void use() {
		System.out.print("물을 사용해서");
		
	}
}

@Configuration
class AppConfig{
	@Bean
	Water water() {
		return new Water();
	}
	
	@Bean
	Airplane airplane() {
		return new Airplane(water());
	}


}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		//Water water = ctx.getBean("water", Water.class);
		Airplane airplane = ctx.getBean("airplane", Airplane.class);
		airplane.fly();
		ctx.close();
		
	}

}

• @Autowired

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;

//의존 관계 (Airplane-Water)
class Airplane{
	@Autowired
	Water water;
		
	void fly() {
		this.water.use();
		System.out.print(" 날아간다.");
	}
	
}


class Water{
	void use() {
		System.out.print("물을 사용해서");
		
	}
}

@Configuration
class AppConfig{
	@Bean
	Water water() {
		return new Water();
	}
	
	@Bean
	Airplane airplane() {
		return new Airplane(water());
	}


}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		Airplane airplane = ctx.getBean("airplane", Airplane.class);
		airplane.fly();
		ctx.close();
		
	}

}

• setter @Autowired

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;

//의존 관계 (Airplane-Water)
class Airplane{
	
	Water water;
	
	@Autowired
	void setWater(Water water) {
		this.water = water;
	}
	
	void fly() {
		this.water.use();
		System.out.print(" 날아간다.");
	}
	
}


class Water{
	void use() {
		System.out.print("물을 사용해서");
		
	}
}

@Configuration
class AppConfig{
	@Bean
	Water water() {
		return new Water();
	}
	
	@Bean
	Airplane airplane() {
		return new Airplane();
	}


}

public class Hello {

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		Airplane airplane = ctx.getBean("airplane", Airplane.class);
		airplane.fly();
		ctx.close();
		
	}

}

• 객체가 없는 경우

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;



//의존 관계 (Airplane-Water)
class Airplane{
	
	Water water;
	
	@Autowired
	void setWater(Water water) {
		this.water = water;
	}
	
	void fly() {
		this.water.use();
		System.out.print(" 날아간다.");
	}
	
}


class Water{
	void use() {
		System.out.print("물을 사용해서");
		
	}
}

@Configuration
class AppConfig{
	@Bean
	Water water() {
		return new Water();
	}
	
//	@Bean
//	Airplane airplane() {
//		return new Airplane();
//	}


}

public class Hello {
	
	

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		Airplane airplane = ctx.getBean("airplane", Airplane.class);
		airplane.fly();
		ctx.close();
		
	}

}

@Component & @ComponentScan

참고

• 객체가 없는 경우 자동적으로 생성시켜버린다.

  • 클래스 명을 소문자로해서

• @ComponentScan

  • 스프링 3.1부터 도입된 Annotation이며 스캔 위치를 설정하고,

  • 어떤 Annotation을 스캔할지 또는 하지 않을지 결정하는 Filter 기능을 가지고있다.

• @Component

  • 컴포넌트 스캔이 스캐닝하는 기준

  • @Component를 들고있는 클래스들이 스캐닝되고, Bean으로 등록된다.

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;

@Component
//의존 관계 (Airplane-Water)
class Airplane{
	
	Water water;
	
	@Autowired
	void setWater(Water water) {
		this.water = water;
	}
	
	void fly() {
		this.water.use();
		System.out.print(" 날아간다.");
	}
	
}


class Water{
	void use() {
		System.out.print("물을 사용해서");
		
	}
}

@Configuration
@ComponentScan
class AppConfig{
	@Bean
	Water water() {
		return new Water();
	}



}

public class Hello {
	
	

	public static void main(String[] args) {

		AnnotationConfigApplicationContext ctx = 
				new AnnotationConfigApplicationContext(AppConfig.class);

		Airplane airplane = ctx.getBean("airplane", Airplane.class);
		airplane.fly();
		ctx.close();
		
	}

}

3. XML

참조

스프링 컨테이너는 다양한 형식의 설정 정보(Config)를 받을 수 있다.
ex) 자바코드, XML, Groovy 등

• 권장사항: 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">

</beans>

<button></button>
//컴파일시
Button button = new Button();

4. DAO, DTO, VO, Entity

DAO (Data Access Object), DTO(Data Transfer Object), VO(Value Object), Entity

• https://velog.io/@corone_hi/DAO-Data-Access-Object-DTOData-Transfer-Object-VOValue-Object
  
  

• 클래스 구성

  • Member: Entity 클래스의 역할

  • MemberDao: CRUD 담당

    CRUD는 CRUD만 해야한다. 즉 다른 예외처리 등을 해서는 안된다.

  • RegisterRequest: VO 클래스의 역할

  • MemberRegisterService: MemberDao를 서포트해주는 역할

    • 즉 DAO에서 일어난 CRUD에 대해 예외처리와 return 값을 이용하는 곳

ex1) VO class

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;

class FormDTO{
	String name;
	FormDTO(){
		
	}
}

//VO class
class RegisterRequest{
	String name;
	RegisterRequest(String name){
		this.name = name;
	}
}

public class Hello {
	
	

	public static void main(String[] args) {

		//1. 클라이언트에서 데이터를 전송
		//2. 서버에서는 DTO 클래스로 값을 얻게 된다.
		//3. String name = DTO객체.name;
		//4. 키보드에서 input을 받는다. (input이 DTO 데이터이다.)
		String inputName = "홍길동";
		RegisterRequest rr = new RegisterRequest(inputName);
		
//		GenericXmlApplicationContext ctx = new GenericXmlApplicationContext("classpath:Context.xml");		
//		ctx.close();
		
	}

}

ex2) Entity class

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;

class FormDTO{
	String name;
	FormDTO(){
		
	}
}

//VO class
class RegisterRequest{
	String name;
	RegisterRequest(String name){
		//데이터 검증 코드가 상당부분 생략되었다.
		this.name = name + "독수리"; //가공
	}
}


//Entity class
//class Entity{
//	int id;
//}

//class Member extends Entity{
class Member{
	int id;
	String name;
}



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

		//1. 클라이언트에서 데이터를 전송
		//2. 서버에서는 DTO 클래스로 값을 얻게 된다.
		//3. String name = DTO객체.name;
		//4. 키보드에서 input을 받는다. (input이 DTO 데이터이다.)
		String inputName = "홍길동";
		RegisterRequest rr = new RegisterRequest(inputName);
		
		//Entitiy에 정보 입력
		Member member = new Member();
		member.id = 1000;
		member.name = rr.name;
		
		//member -> DB에 저장(Map Collection 사용)
		
		
//		GenericXmlApplicationContext ctx = new GenericXmlApplicationContext("classpath:Context.xml");		
//		ctx.close();
		
	}

}

ex3) DAO class

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;

class FormDTO{
	String name;
	FormDTO(){
		
	}
}

//VO class
class RegisterRequest{
	String name;
	RegisterRequest(String name){
		//데이터 검증 코드가 상당부분 생략되었다.
		this.name = name + "독수리"; //가공
	}
}


//Entity class
//class Entity{
//	int id;
//}

//class Member extends Entity{
class Member{
	int id;
	String name;
}



//DAO class
class MemberDao{
	void insert(Member member) {
		//쿼리 문장을 사용하는 코드이지만 
		System.out.println(member.name + "DB에 저장하였습니다.");
	}
	
}

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

		//1. 클라이언트에서 데이터를 전송
		//2. 서버에서는 DTO 클래스로 값을 얻게 된다.
		//3. String name = DTO객체.name;
		//4. 키보드에서 input을 받는다. (input이 DTO 데이터이다.)
		String inputName = "홍길동";
		RegisterRequest rr = new RegisterRequest(inputName);
		
		//Entitiy에 정보 입력
		Member member = new Member();
		member.id = 1000;
		member.name = rr.name;
		
		//member -> DB에 저장(Map Collection 사용)
		MemberDao memberDao = new MemberDao();
		memberDao.insert(member);
		
//		GenericXmlApplicationContext ctx = new GenericXmlApplicationContext("classpath:Context.xml");		
//		ctx.close();
		
	}

}

ex4) Service 클래스

Dao와의 차이점은 리턴값을 받아서 어떠한 판단을하게 된다.

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;

class FormDTO{
	String name;
	FormDTO(){
		
	}
}

//VO class
class RegisterRequest{
	String name;
	RegisterRequest(String name){
		//데이터 검증 코드가 상당부분 생략되었다.
		this.name = name + "독수리"; //가공
	}
}


//Entity class
//class Entity{
//	int id;
//}

//class Member extends Entity{
class Member{
	int id;
	String name;
}



//DAO class
class MemberDao{
	void insert(Member member) {
		//쿼리 문장을 사용하는 코드이지만 
		System.out.println(member.name + "DB에 저장하였습니다.");
	}
	
}

class MemberRegisterService{
	MemberDao memberDao;
	MemberRegisterService(MemberDao memberDao){
		this.memberDao = memberDao;
	}
	
	void register(Member member) {
		memberDao.insert(member);
	}
}

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

		//1. 클라이언트에서 데이터를 전송
		//2. 서버에서는 DTO 클래스로 값을 얻게 된다.
		//3. String name = DTO객체.name;
		//4. 키보드에서 input을 받는다. (input이 DTO 데이터이다.)
		String inputName = "홍길동";
		RegisterRequest rr = new RegisterRequest(inputName);
		
		//Entitiy에 정보 입력
		Member member = new Member();
		member.id = 1000;
		member.name = rr.name;
		
		MemberRegisterService mrs = new MemberRegisterService(new MemberDao());
		
		//member -> DB에 저장(Map Collection 사용)
		MemberDao memberDao = new MemberDao();
		memberDao.insert(member);
		
//		GenericXmlApplicationContext ctx = new GenericXmlApplicationContext("classpath:Context.xml");		
//		ctx.close();
		
	}

}

ex5) register 함수 변경

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;

class FormDTO{
	String name;
	FormDTO(){
		
	}
}

//VO class
class RegisterRequest{
	String name;
	RegisterRequest(String name){
		//데이터 검증 코드가 상당부분 생략되었다.
		this.name = name + "독수리"; //가공
	}
}


//Entity class
//class Entity{
//	int id;
//}

//class Member extends Entity{
class Member{
	int id;
	String name;
}



//DAO class
class MemberDao{
	boolean insert(Member member) {
		//쿼리 문장을 사용하는 코드이지만 
		System.out.println(member.name + "DB에 저장하였습니다.");
		return true;
	}
	
}

class MemberRegisterService{
	MemberDao memberDao;
	public MemberRegisterService(MemberDao memberDao){
		this.memberDao = memberDao;
	}
	
	void register(RegisterRequest rr) {
		
		
		//Entitiy에 정보 입력
		Member member = new Member();
		member.id = 1000;
		member.name = rr.name;
		
		if(memberDao.insert(member) == true) {
			System.out.println("모든 작업이 정상입니다.");
		}
		
	}
}

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

		//1. 클라이언트에서 데이터를 전송
		//2. 서버에서는 DTO 클래스로 값을 얻게 된다.
		//3. String name = DTO객체.name;
		//4. 키보드에서 input을 받는다. (input이 DTO 데이터이다.)
		String inputName = "홍길동";
		RegisterRequest rr = new RegisterRequest(inputName);
		MemberRegisterService mrs = new MemberRegisterService(new MemberDao());
		
		mrs.register(rr);
		
		//member -> DB에 저장(Map Collection 사용)
//		MemberDao memberDao = new MemberDao();
//		memberDao.insert(rr);
		
//		GenericXmlApplicationContext ctx = new GenericXmlApplicationContext("classpath:Context.xml");		
//		ctx.close();
		
	}

}

ex6) Spring으로 변경

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;

class FormDTO{
	String name;
	FormDTO(){
		
	}
}

//VO class
class RegisterRequest{
	String name;
	RegisterRequest(String name){
		//데이터 검증 코드가 상당부분 생략되었다.
		this.name = name + "독수리"; //가공
	}
}


//Entity class
//class Entity{
//	int id;
//}

//class Member extends Entity{
class Member{
	int id;
	String name;
}



//DAO class
class MemberDao{
	boolean insert(Member member) {
		//쿼리 문장을 사용하는 코드이지만 
		System.out.println(member.name + "DB에 저장하였습니다.");
		return true;
	}
	
}

class MemberRegisterService{
	@Autowired
	MemberDao memberDao;
//	public MemberRegisterService(MemberDao memberDao){
//		this.memberDao = memberDao;
//	}
//	
	void register(RegisterRequest rr) {
		
		
		//Entitiy에 정보 입력
		Member member = new Member();
		member.id = 1000;
		member.name = rr.name;
		
		if(memberDao.insert(member) == true) {
			System.out.println("모든 작업이 정상입니다.");
		}
		
	}
}


@Configuration
class AppConfig{
	@Bean
	MemberDao memberDao() {
		return new MemberDao();
	}
	@Bean
	MemberRegisterService memberRegisterService() {
		//return new MemberRegisterService(memberDao());
		return new MemberRegisterService();
	}
	
}

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

		//1. 클라이언트에서 데이터를 전송
		//2. 서버에서는 DTO 클래스로 값을 얻게 된다.
		//3. String name = DTO객체.name;
		//4. 키보드에서 input을 받는다. (input이 DTO 데이터이다.)
//		String inputName = "홍길동";
//		RegisterRequest rr = new RegisterRequest(inputName);
//		
		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
		MemberRegisterService mrs = ctx.getBean("memberRegisterService", MemberRegisterService.class);
		mrs.register(new RegisterRequest("홍길동"));
		ctx.close();
		
//		MemberRegisterService mrs = new MemberRegisterService(new MemberDao());
//		mrs.register(rr);
		
		//member -> DB에 저장(Map Collection 사용)
//		MemberDao memberDao = new MemberDao();
//		memberDao.insert(rr);

	}

}

ex6) Spring 아닐 때 Config

package Pack;

import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.GenericXmlApplicationContext;
import org.springframework.lang.Nullable;
import org.springframework.stereotype.Component;

class FormDTO{
	String name;
	FormDTO(){
		
	}
}

//VO class
class RegisterRequest{
	String name;
	RegisterRequest(String name){
		//데이터 검증 코드가 상당부분 생략되었다.
		this.name = name + "독수리"; //가공
	}
}


//Entity class
//class Entity{
//	int id;
//}

//class Member extends Entity{
class Member{
	int id;
	String name;
}



//DAO class
class MemberDao{
	boolean insert(Member member) {
		//쿼리 문장을 사용하는 코드이지만 
		System.out.println(member.name + "DB에 저장하였습니다.");
		return true;
	}
	
}

class MemberRegisterService{
	MemberRegisterService(MemberDao memberDao){
		this.memberDao = memberDao;
	}
	MemberDao memberDao;
//	public MemberRegisterService(MemberDao memberDao){
//		this.memberDao = memberDao;
//	}
//	
	void register(RegisterRequest rr) {
		
		
		//Entitiy에 정보 입력
		Member member = new Member();
		member.id = 1000;
		member.name = rr.name;
		
		if(memberDao.insert(member) == true) {
			System.out.println("모든 작업이 정상입니다.");
		}
		
	}
}


//config
class Assemble{
	MemberRegisterService f1() {
		MemberRegisterService mrs = new MemberRegisterService(new MemberDao());
		mrs.register(new RegisterRequest("홍길동"));
		return mrs;
	}
}

//@Configuration
//class AppConfig{
//	@Bean
//	MemberDao memberDao() {
//		return new MemberDao();
//	}
//	@Bean
//	MemberRegisterService memberRegisterService() {
//		//return new MemberRegisterService(memberDao());
//		return new MemberRegisterService(new MemberDao());
//	}
//	
//}

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

		//1. 클라이언트에서 데이터를 전송
		//2. 서버에서는 DTO 클래스로 값을 얻게 된다.
		//3. String name = DTO객체.name;
		//4. 키보드에서 input을 받는다. (input이 DTO 데이터이다.)

		Assemble a = new Assemble();
		MemberRegisterService msr = a.f1();
		msr.register(new RegisterRequest("홍길동"));
		
//		String inputName = "홍길동";
//		RegisterRequest rr = new RegisterRequest(inputName);
//		MemberRegisterService mrs = new MemberRegisterService(new MemberDao());
//		mrs.register(rr);

//		
//		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfig.class);
//		MemberRegisterService mrs = ctx.getBean("memberRegisterService", MemberRegisterService.class);
//		mrs.register(new RegisterRequest("홍길동"));
//		ctx.close();
		
		
		//member -> DB에 저장(Map Collection 사용)
//		MemberDao memberDao = new MemberDao();
//		memberDao.insert(rr);

	}

}

이제는 선택

• CRUD를 클래스로 분리시키기
• 현재코드에 구현하기