리플렉션 - 활용 예제

- 필드 값이 null 이 되면 안된다는 가정을 하자

package reflection.data;

public class Team {

    private String id;
    private String name;

    public Team() {
    }

    public Team(String id, String name) {
        this.id = id;
        this.name = name;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Team{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                '}';
    }
}

package reflection.data;

public class User {
    private String id;
    private String name;
    private Integer age;

    public User() {
    }

    public User(String id, String name, Integer age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

 

 

- FieldUtil 생성

package reflection;

import java.lang.reflect.Field;

public class FieldUtil {

    public static void nullFieldToDefault(Object target) throws IllegalAccessException {
        Class<?> aClass = target.getClass();
        Field[] declaredFields = aClass.getDeclaredFields();
        for (Field field : declaredFields) {
            field.setAccessible(true);
            if (field.get(target) != null) {
                continue;
            }

            if (field.getType() == String.class) {
                field.set(target, "");
            } else if (field.getType() == Integer.class) {
                field.set(target, 0);
            }
        }
    }
}

package reflection;

import reflection.data.Team;
import reflection.data.User;

public class FieldV4 {

    public static void main(String[] args) throws IllegalAccessException {
        User user = new User("id1", null, null);
        Team team = new Team("team1", null);
        System.out.println("===== before =====");
        System.out.println("user = " + user);
        System.out.println("team = " + team);

        FieldUtil.nullFieldToDefault(user);
        FieldUtil.nullFieldToDefault(team);
        System.out.println("===== after =====");
        System.out.println("user = " + user);
        System.out.println("team = " + team);
    }
}