Java 序列化

1. Java 原生序列化

• 序列化：把内存中数据写入文件中
• 反序列化：从文件中读取数据到内存中
• 使用流传输对象的过程称为序列化、反序列化

2. 序列化使用

// 必须实现 Serializable 接口，否则会报错 java.io.NotSerializableException
public class Student implements Serializable {
    // 序列化版本号，保证序列化和反序列化的是同一个类
    private static final long serialVersionUID = -3881208742057626511L;
}

    // 序列化
    ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("src/main/resources/student.bin"));
    Student student = new Student("tinyspot", 20);
    out.writeObject(student);
    out.close();

    // 反序列化
    ObjectInputStream ois = new ObjectInputStream(new FileInputStream("src/main/resources/student.bin"));
    Student student = (Student) ois.readObject();
    ois.close();
    System.out.println(JSON.toJSONString(student));

2.1 绕过 transient

会通过反射调用 readObject(java.io.ObjectInputStream s) 和 writeObject(java.io.ObjectOutputStream s)

public class User implements Serializable {
    private static final long serialVersionUID = -5324601100478775753L;
    private transient String name;
    private Integer age;

    private void readObject(java.io.ObjectInputStream s) throws IOException, ClassNotFoundException {
        s.defaultReadObject();
        s.readObject();
    }

    private void writeObject(java.io.ObjectOutputStream s) throws IOException {
        s.defaultWriteObject();
        s.writeObject(name);
    }
}

3. 示例

public static void main(String[] args) {
    ISerializer serializer = new FileSerializer();
    User user = new User("Tinyspot", 20);
    serializer.serializer(user);

    User result = serializer.deSerializer(null, null);
    System.out.println(result);
}

public interface ISerializer {
    
    <T> byte[] serializer(T obj);

    <T> T deSerializer(byte[] data, Class<T> clazz);
}

public class JavaSerialier implements ISerializer {

    @Override
    public <T> byte[] serializer(T obj) {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        try {
            ObjectOutputStream outputStream = new ObjectOutputStream(byteArrayOutputStream);
            outputStream.writeObject(obj);
            return byteArrayOutputStream.toByteArray();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return new byte[0];
    }

    @Override
    public <T> T deSerializer(byte[] data, Class<T> clazz) {
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(data);
        try {
            ObjectInputStream inputStream = new ObjectInputStream(byteArrayInputStream);
            return (T) inputStream.readObject();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return null;
    }
}

public class FileSerializer implements ISerializer {
    @Override
    public <T> byte[] serializer(T obj) {
        try {
            ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream(new File("src/main/resources/user")));
            outputStream.writeObject(obj);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return new byte[0];
    }

    @Override
    public <T> T deSerializer(byte[] data, Class<T> clazz) {
        try {
            ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream(new File("src/main/resources/user")));
            return (T) inputStream.readObject();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return null;
    }
}