3-1 Spring DI 흉내내기(1)

Spring DI 흉내내기

1. 변경에 유리한 코드(1) - 다형성, factory method

//변경 포인트 2개
SportsCar car = new SportsCar();
--> Truck car = new Truck();

==>

//다형성 --> 변경에 유리
//변경 포인트 1개
Car car = new SportsCar();
--> Car car = new Truck();

==>

Car car = getCar(); // getCar()메서드 하나만 고치면 됨
static Car getCar() {
	return new SportsCar();
}

2. 변경에 유리한 코드(2) - Map과 외부 파일

Main1.java

package com.fastcampus.ch3.diCopy1;

import java.io.FileReader;
import java.util.Properties;

class Car {}
class Truck extends Car {}
class SportsCar extends Car{}
class Engine {}

public class Main1 {
    public static void main(String[] args) throws Exception {
        Car car = (Car)getObject("car");
        Engine engine = (Engine)getObject("engine");
        System.out.println("car = " + car);
        System.out.println("engine = " + engine);
    }

    static Car getCar() throws Exception {
        Properties p = new Properties();
        p.load(new FileReader("config.txt"));

        Class clazz = Class.forName(p.getProperty("car"));

        return (Car)clazz.newInstance();
    }

    static Object getObject(String key) throws Exception {
        Properties p = new Properties();
        p.load(new FileReader("config.txt"));

        Class clazz = Class.forName(p.getProperty(key));

        return clazz.newInstance();
    }
}

config.txt

car=com.fastcampus.ch3.diCopy1.SportsCar
engine=com.fastcampus.ch3.diCopy1.Engine