Java 직렬화 기초

Java 직렬화란 무엇인가

Serializable 마커 인터페이스

import java.io.Serializable;
public class User implements Serializable {
    private String name;
    private int age;
    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }
    @Override public String toString() { return name + " / " + age; }
}

ObjectOutputStream으로 객체 쓰기

import java.io.*;
try (ObjectOutputStream oos = new ObjectOutputStream(
        new FileOutputStream("user.ser"))) {
    oos.writeObject(new User("Alice", 30));
    System.out.println("Serialized successfully");
}

ObjectInputStream으로 객체 읽기

import java.io.*;
try (ObjectInputStream ois = new ObjectInputStream(
        new FileInputStream("user.ser"))) {
    User u = (User) ois.readObject();
    System.out.println("Deserialized: " + u);
}

객체 그래프 직렬화

public class Order implements Serializable {
    private User customer;   // User must be Serializable
    private List<String> items;
    public Order(User customer, List<String> items) {
        this.customer = customer;
        this.items = items;
    }
}

NotSerializableException

// Thread is NOT Serializable
public class Task implements Serializable {
    private Thread worker; // throws NotSerializableException!
    // Fix: mark as transient
    private transient Thread worker2;
}

객체 그래프와 공유 참조

컬렉션 직렬화

List<String> names = new ArrayList<>(List.of("Alice", "Bob"));
try (ObjectOutputStream oos = new ObjectOutputStream(
        new FileOutputStream("names.ser"))) {
    oos.writeObject(names);
}

상속과 직렬화

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