[Spring] DI 기본예제 1 - BMI 계산기

- DI란?

 

DI는 Dependency Injection의 줄임말, 의존관계 주입이라고 한다.

 

여기서 의존관계 주입이란, 어떠한 대상이 변하면 그것에 의존하는 대상 또한 영향을 미친다는 의미이다.

 

예를 들어, A라는 친구가 B에 의존하는데, B가 바뀌면 A 친구 또한 영향이 미친다는 뜻이다.

 

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- BMI 계산기 구현하기

 

< MyInfo.java >

package com.javalec.ex;
 
import java.util.ArrayList;
 
public class MyInfo {
    private  String name;
    private double height;
    private double weight;
    private ArrayList<String> hobby;
    private BMICal bmiclass;
   
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public double getHeight() {
        return height;
    }
    public void setHeight(double height) {
        this.height = height;
    }
    public double getWeight() {
        return weight;
    }
    public void setWeight(double weight) {
        this.weight = weight;
    }
    public ArrayList<String> getHobby() {
        return hobby;
    }
    public void setHobby(ArrayList<String> hobby) {
        this.hobby = hobby;
    }
    public BMICal getBmiclass() {
        return bmiclass;
    }
    public void setBmiclass(BMICal bmiclass) {
        this.bmiclass = bmiclass;
    }
    
    public void bmiCalculation() {
        bmiclass.bmicalculation(weight, height);
    }
 
    public void getInfo() {
        System.out.println("이름 : " + name);
        System.out.println("키 : " + height);
        System.out.println("몸무게 : " + weight);
        System.out.println("취미 : " + hobby);
        bmiCalculation();
    } 
}

 

< BMICal.java >

package com.javalec.ex;
 
import java.util.ArrayList;
 
public class BMICal {
        private double lowWeight;
        private double nomal;
        private double overWeight;
        private double obesty;
 
        public void bmicalculation(double weight, double height) {
            double h = height * 0.01 ;
            double result = weight / (h*h);
           
            System.out.println("BMI 지수 :  " + (int)result);
       
            if(result > obesty) {
                    System.out.println("비만입니다.");
            } else if (result > overWeight) {
                System.out.println("과체중입니다");
            }else if (result > nomal) {
                    System.out.println("정상입니다");
            } else {
                System.out.println("저체중입니다");
            }
       
        }
 
        public double getLowWeight() {
            return lowWeight;
        }
 
        public void setLowWeight(double lowWeight) {
            this.lowWeight = lowWeight;
        }
 
        public double getNomal() {
            return nomal;
        }
 
        public void setNomal(double nomal) {
            this.nomal = nomal;
        }
 
        public double getOverWeight() {
            return overWeight;
        }
 
        public void setOverWeight(double overWeight) {
            this.overWeight = overWeight;
        }
 
        public double getObesty() {
            return obesty;
        }
 
        public void setObesty(double obesty) {
            this.obesty = obesty;
        }
}

 

< applicationCTX.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">
 
    <bean id = "bmiCal" class="com.javalec.ex.BMICal">
        <property name="lowWeight">
            <value>18.5 </value>
        </property>
        <property name="nomal">
            <value>23</value>
        </property>
        <property name="overWeight">
            <value>25</value>
        </property>
        <property name="obesty">
            <value>330</value>
        </property>
    </bean>
   
    <bean id="myInfo" class="com.javalec.ex.MyInfo">
        <property name="name">
            <value>홍길동</value>
        </property>
        <property name="height">
            <value>178</value>
        </property>
        <property name="weight">
            <value>68</value>
        </property>
        <property name="hobby">
            <list>
                <value>운동</value>
                <value>낮잠</value>
            </list>
        </property>
        <property name="bmiclass">
            <ref bean="bmiCal"/>
        </property>
    </bean>
</beans>

 

list 타입은 <property> 선언 한 후, <list>로 묶어 <value>를 통해 작성한다.

 

< MainClass.java >

package com.javalec.ex;
 
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.GenericXmlApplicationContext;
 
public class MainClass {
    public static void main(String[] args) {
       
        String configLocation = "classpath:applicationCTX.xml";
        AbstractApplicationContext ctx = new GenericXmlApplicationContext(configLocation);
        MyInfo myinfo = ctx.getBean("myInfo", MyInfo.class);
        
        myinfo.getInfo();
 
        ctx.close();
    }
}

 

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- 결과물