DI 생성자 주입

https://blog.naver.com/drv982/222900664820

[DI] 생성자 주입

Dependency Injection 의존성 주입

A객체를 만들려고 하는데 B객체가 필요할경우 

스프링 프레임워크에서는 B객체를 자동으로 만들어줌 

 

이런거를 의존성 주입이라고 함. 

 

 

 

 

---

 

DI 생성

 

 

 

 

 

 

pom.xml 복사 붙여넣기

 

 

maven 업데이트

 

 

패키지도 3개 다 복사함

 

안의 내용 다 지우기

 

 

 

TestBean

 

 

package com.demo.beans;

public class TestBean {
	private int data1;
	private double data2;
	private String data3;

	// 기본 생성자 
	public TestBean() {
		System.out.println("TestBean의 기본 생성자");
		this.data1 = 0;
		this.data2 = 0.0;
		this.data3 = null;
	}
	
	public TestBean(int data1) {
		System.out.println("TestBean의 생성자 : int 변수 1");
		this.data1 = data1;
		this.data2 = 0.0;
		this.data3 = null;
	}
	
	public TestBean(double data2) {
		System.out.println("TestBean의 생성자 : double 변수 1");
		this.data1 = 0;
		this.data2 = data2;
		this.data3 = null;
	}
	
	public TestBean(String data3) {
		System.out.println("TestBean의 생성자 : String 변수 1");
		this.data1 = 0;
		this.data2 = 0.0;
		this.data3 = data3;
	}
	

	public TestBean(int data1, double data2, String data3) {
		System.out.println("TestBean의 생성자 : 변수 3개");
		this.data1 = data1;
		this.data2 = data2;
		this.data3 = data3;
	}

	

	// 출력 메소드
	public void printData() {
		System.out.printf("data1 : %d\n", data1);
		System.out.printf("data2 : %f\n", data2);
		System.out.printf("data3 : %s\n", data3);
	}
	


}

 

 

 

모든 생성자 사용 

 

 

 

 

 

 

beans.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">


	<!-- 기본 생성자  : 매개변수 없음 -->
	<bean id='obj1' class='com.demo.beans.TestBean' lazy-init='true' />


	<!--시작 태그와 종료 태그 사이에 생성자 -->
	<!-- 생성자 입력변수로 정수(int) 100이 입력됨.  -->
	<bean id='obj2' class='com.demo.beans.TestBean' lazy-init='true'>
		<constructor-arg value='100' type='int' />
	</bean>
	
	<!-- 생성자 입력변수로 실수(double) 11.11이 입력됨.  -->
	<bean id='obj3' class='com.demo.beans.TestBean' lazy-init='true'>
		<constructor-arg value='11.11' type='double' />
	</bean>

	<!-- 생성자 입력변수로 문자열(String)이 입력됨.  -->
	<bean id='obj4' class='com.demo.beans.TestBean' lazy-init='true'>
		<constructor-arg value='문자열' />
	</bean>


	<!-- 생성자 입력변수로 정수,실수,문자열 모두 입력됨.  -->
	<bean id='obj5' class='com.demo.beans.TestBean' lazy-init='true'>
		<constructor-arg value='200' type='int' />
		<constructor-arg value='22.22' type='double' />
		<constructor-arg value='안녕하세요' type='java.lang.String' />
	</bean>
</beans>

 

 

 

 

 

 

main 

package com.demo.main;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.demo.beans.TestBean;

public class MainClass {

	public static void main(String[] args) {
		// beans.xml 파일을 로딩한다
		ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("com/demo/config/beans.xml");

		TestBean obj1 = ctx.getBean("obj1", TestBean.class);
		obj1.printData();

		System.out.println("--------------------------");

		TestBean obj2 = ctx.getBean("obj2", TestBean.class);
		obj2.printData();

		System.out.println("--------------------------");

		TestBean obj3 = ctx.getBean("obj3", TestBean.class);
		obj3.printData();

		System.out.println("--------------------------");

		TestBean obj4 = ctx.getBean("obj4", TestBean.class);
		obj4.printData();

		System.out.println("--------------------------");

		TestBean obj5 = ctx.getBean("obj5", TestBean.class);
		obj5.printData();

		System.out.println("--------------------------");

	}

}

 

 

출력

15:18:39.645 [main] DEBUG org.springframework.context.support.ClassPathXmlApplicationContext - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@32d2fa64
15:18:39.791 [main] DEBUG org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loaded 5 bean definitions from class path resource [com/demo/config/beans.xml]
15:18:39.830 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'obj1'
TestBean의 기본 생성자
data1 : 0
data2 : 0.000000
data3 : null
--------------------------
15:18:39.843 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'obj2'
TestBean의 생성자 : int 변수 1
data1 : 100
data2 : 0.000000
data3 : null
--------------------------
15:18:39.862 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'obj3'
TestBean의 생성자 : double 변수 1
data1 : 0
data2 : 11.110000
data3 : null
--------------------------
15:18:39.864 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'obj4'
TestBean의 생성자 : String 변수 1
data1 : 0
data2 : 0.000000
data3 : 문자열
--------------------------
15:18:39.866 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'obj5'
TestBean의 생성자 : 변수 3개
data1 : 200
data2 : 22.220000
data3 : 안녕하세요
--------------------------

 

 

 

 

 

beans.xml 추가

obj8~9

	<!-- 테스트빈2는 객체를 입력받음. -->
	<bean id='obj8' class='com.demo.beans.TestBean2' lazy-init='true'>
		<constructor-arg>
			<bean class='com.demo.beans.DataBean' />
		</constructor-arg>
		<constructor-arg>
			<bean class='com.demo.beans.DataBean' />
		</constructor-arg>
	</bean>

	<bean id='data_bean' class='com.demo.beans.DataBean'
		scope='prototype' />
	<!-- 위의 data_bean 객체를 자동 주입받는다. 객체 두 번 생성  -->
	<bean id='obj9' class='com.demo.beans.TestBean2' lazy-init='true'>
		<constructor-arg ref='data_bean' />
		<constructor-arg ref='data_bean' />
	</bean>

 

 

DataBean

package com.demo.beans;

public class DataBean {

}

TestBean2

package com.demo.beans;

public class TestBean2 {
	
	//DataBean 객체를 변수를 선언함 
	private DataBean data1;
	private DataBean data2;
	
	//생성 시 DataBean 객체를 입력 받는다. 
	public TestBean2(DataBean data1, DataBean data2) {
		super();
		this.data1 = data1;
		this.data2 = data2;
	}
	
	// 출력 메소드
	public void printData() {
		System.out.printf("data1 : %s\n", data1);
		System.out.printf("data2 : %s\n", data2);
	}
	

}

 

 

빈 설정으로 값을 주입하는 방법이 생성자 변수로 

obj8-9 객체를 주입받음

생성자 주입으로 객체를 주입받음 

 

 

 

main에서 테스트

 

		TestBean2 obj8 = ctx.getBean("obj8", TestBean2.class);
		obj8.printData();

		System.out.println("-------------------------------");

		TestBean2 obj9 = ctx.getBean("obj9", TestBean2.class);
		obj9.printData();

		ctx.close();

--------------------------
15:40:10.031 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'obj8'
data1 : com.demo.beans.DataBean@1ed6388a
data2 : com.demo.beans.DataBean@5a45133e
-------------------------------
15:40:10.033 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'obj9'
data1 : com.demo.beans.DataBean@60bd273d
data2 : com.demo.beans.DataBean@121314f7
15:40:10.038 [main] DEBUG org.springframework.context.support.ClassPathXmlApplicationContext - Closing org.springframework.context.support.ClassPathXmlApplicationContext@32d2fa64, started on Wed Oct 18 15:40:09 KST 2023