Java Reflection 으로 인스턴스 생성하는 예시

아래는 테스트 코드

package com.kakao.keyword;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

public class ReflectionTest<T> {

    private Class<T> clazz;

    @BeforeEach
    public void init() {
        clazz = (Class<T>) TestClass.class;
    }

    @Test
    public void test() throws Exception {
        T instance = clazz.getDeclaredConstructor().newInstance();

        Field[] fields = clazz.getDeclaredFields();
        for (int i = 0; i < fields.length; i++) {
            System.out.println(fields[i].getName() + ", " + fields[i].getType());
            injectValue(instance, fields[i]);
            System.out.println(callGetter(instance, fields[i].getName()));
        }
    }

    private void injectValue(Object obj, Field field) {
        Class<?> typeClass = field.getType();
        String fieldName = field.getName();

        if (typeClass == Integer.class) {
            callSetter(obj, fieldName, 10);
        } else if (typeClass == Long.class) {
            callSetter(obj, fieldName, 20L);
        } else {
            callSetter(obj, fieldName, "string");
        }
    }

    private void callSetter(Object obj, String field, Object value) {
        PropertyDescriptor pd;
        try {
            pd = new PropertyDescriptor(field, obj.getClass());
            pd.getWriteMethod().invoke(obj, value);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private Object callGetter(Object obj, String field) {
        PropertyDescriptor pd;
        try {
            pd = new PropertyDescriptor(field, obj.getClass());
            return pd.getReadMethod().invoke(obj);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

	//getter, setter 는 lombok 으로 대체하는게 코드 수가 줄어 좋음.
    static class TestClass {

        private String memberString;
        private Long memberLong;
        private Integer memberInteger;

        public String getMemberString() {
            return this.memberString;
        }

        public void setMemberString(String memberString) {
            this.memberString = memberString;
        }

        public Long getMemberLong() {
            return this.memberLong;
        }

        public void setMemberLong(Long memberLong) {
            this.memberLong = memberLong;
        }

        public Integer getMemberInteger() {
            return this.memberInteger;
        }

        public void setMemberInteger(Integer memberInteger) {
            this.memberInteger = memberInteger;
        }
    }

}

 

결과

memberString, class java.lang.String
string
memberLong, class java.lang.Long
20
memberInteger, class java.lang.Integer
10