[Java] 자바 리플렉션, 예제

리플렉션 3줄요약

- 리플렉션은 일종의 API임. 런타임 중에 interface, class들, method들의 행동 과 필드들을 조사하거나 수정할 수 있도록 해줌.

- 리플렉션을 적용할 클래스는 java.lang.reflect pacakge가 제공되어야함.

- 리플렉션을 통해, 런타임에 method를 부를 수 있음, 그것의 접근 지정자와 상관없이.

 

 

 

예제 1. static 필드 접근하기.

import java.lang.reflect.Field;

public class test00 {

    public static void main(String[] args) throws Exception {
        Employee employee = new Employee();
        Object object = employee;
        Field field = object.getClass().getField("salary");
        
        field.set(object, 11221);
        
        System.out.println("Value of salary after "
                + "applying set is "
                + employee.salary);        
    }
}

class Employee {
    public static short uniqueNo = 239;
    public static double salary = 121324.13333;
    
    public int age = 3;
}

 

출력

Value of salary after applying set is 11221.0

 

 

예제 2. 필드 접근하기

import java.lang.reflect.Field;

public class test00 {

    public static void main(String[] args) throws Exception {
        Employee employee = new Employee();
        Object object = employee;
        Field field = object.getClass().getField("age");
        
        field.set(object, 35);
        
        System.out.println("Value of salary after "
                + "applying set is "
                + employee.age);        
    }
}

class Employee {
    public static short uniqueNo = 239;
    public static double salary = 121324.13333;
    
    public int age = 3;
}

 

출력

Value of salary after applying set is 35

 

 

 

예제 3

import java.lang.reflect.Field;

public class test00 {

    public static void main(String[] args) throws Exception {
        Employee employee = new Employee();
        Object object = employee;
        Field field = object.getClass().getField("gender");
        
        field.set(object, false);
        
        System.out.println("Value of salary after "
                + "applying set is "
                + employee.gender);        
    }
}

class Employee {
    public static short uniqueNo = 239;
    public static double salary = 121324.13333;
    
    public int age = 3;
    public boolean gender = true;
}

출력

Value of salary after applying set is false