/*
         * 자바 직렬화 : ObjectOutputStream을 이용한다
         */
        Account account = Account.of("jack", "010-7720-7954", 28);
        byte[] serializedAccount;

        try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
            try (ObjectOutputStream oos = new ObjectOutputStream(baos)) {
                oos.writeObject(account);
                serializedAccount = baos.toByteArray();

                // 바이트로 변환된 (직렬화된) 결과를 String으로 인코딩                
                System.out.println(Base64.getEncoder().encodeToString(serializedAccount));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

// seialVersionUID
private static final long serialVersionUID = 1L;

        /*
         * 자바 역직렬화 : ObjectInputStream을 이용한다.
         */
        try (ByteArrayInputStream bais = new ByteArrayInputStream(serializedAccount)) {
            try (ObjectInputStream ois = new ObjectInputStream(bais)) {
                Object objectAccount = ois.readObject();
                Account accountFromSerialized = (Account) objectAccount;
                System.out.println(accountFromSerialized);
            }
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }

@Getter
public class Account implements Serializable {

    private transient String name;
    private String phoneNumber;
    private int age;

public static void main(String[] args) {

        /*
         * 자바 직렬화 : ObjectOutputStream을 이용한다
         */
        Account account = Account.of("jack", "010-7720-7954", 28);
        byte[] serializedAccount = new byte[1000];

        try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
            try (ObjectOutputStream oos = new ObjectOutputStream(baos)) {
                oos.writeObject(account);
                serializedAccount = baos.toByteArray();

                // 바이트로 변환된 (직렬화된) 결과를 String으로 인코딩
                System.out.println(Base64.getEncoder().encodeToString(serializedAccount));
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        /*
         * 자바 역직렬화 : ObjectInputStream을 이용한다.
         */
        try (ByteArrayInputStream bais = new ByteArrayInputStream(serializedAccount)) {
            try (ObjectInputStream ois = new ObjectInputStream(bais)) {
                Object objectAccount = ois.readObject();
                Account accountFromSerialized = (Account) objectAccount;
                System.out.println(accountFromSerialized);
            }
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

public class JackSingleton implements Serializable {
    private static final JackSingleton INSTANCE = new JackSingleton();

    public JackSingleton() {
    }
    
    public static JackSingleton getInstance() {
        return INSTANCE;
    }
}

package com.titanic.javatest.serializable;

import java.io.*;
import java.util.Base64;

public class Serializer {

    public String serialize(Object object) {
        /*
         * 자바 직렬화 : ObjectOutputStream을 이용한다
         */
        byte[] serialized;

        try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
            try (ObjectOutputStream oos = new ObjectOutputStream(baos)) {
                oos.writeObject(object);
                serialized = baos.toByteArray();

                // 바이트로 변환된 (직렬화된) 결과를 String으로 인코딩
                return Base64.getEncoder().encodeToString(serialized);
            }
        } catch (IOException e) {
            e.printStackTrace();
            return "";
        }
    }

    public Object deserialize(String serialized) {
        /*
         * 자바 역직렬화 : ObjectInputStream을 이용한다.
         */
        byte[] serializedSingleton = Base64.getDecoder().decode(serialized);
        try (ByteArrayInputStream bais = new ByteArrayInputStream(serializedSingleton)) {
            try (ObjectInputStream ois = new ObjectInputStream(bais)) {
                Object objectAccount = ois.readObject();
                return objectAccount;
            }
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
            return null;
        }
    }

}

package com.titanic.javatest.serializable;

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import static org.assertj.core.api.Assertions.assertThat;

public class readResolveTest {

    private JackSingleton jackSingleton;
    private Serializer serializer;

    @BeforeEach
    void setUp() {
        this.jackSingleton = JackSingleton.getInstance();
        this.serializer = new Serializer();
    }

    @Test
    void 일반직렬화를_테스트한다() throws Exception {
        // when
        String serialized = serializer.serialize(jackSingleton);
        JackSingleton deserialized = (JackSingleton) serializer.deserialize(serialized);

        // then
        assertThat(deserialized).isSameAs(jackSingleton);
        assertThat(deserialized).isEqualTo(jackSingleton);
    }

    @Test
    void readResolve를_테스트한다() throws Exception {
        // when
        String serialized = serializer.serialize(jackSingleton);
        JackSingleton deserialized = (JackSingleton) serializer.deserialize(serialized);

        // then
        assertThat(deserialized).isSameAs(jackSingleton);
        assertThat(deserialized).isEqualTo(jackSingleton);
    }
}

package com.titanic.javatest.serializable;

import java.io.Serializable;

public class JackSingleton implements Serializable {
    private static final JackSingleton INSTANCE = new JackSingleton();

    public JackSingleton() {
    }

    public static JackSingleton getInstance() {
        return INSTANCE;
    }

    private Object readResolve() {
        return INSTANCE;
    }
}