Serializable 和 Externalizable区别？

Serializable接口

java.io.Serializable 接口没有方法或字段，仅用于标识可序列化的语义。

public interface Serializable {
}

可序列化类的所有子类型本身都是可序列化的。在进行序列化操作时，会判断要被序列化的类是否是Enum、Array和 Serializable类型，如果都不是则直接抛出NotSerializableException。

@Data
public class A1_User implements Serializable {private String name;private int age;
}

A1_User user = new A1_User();
user.setName("xiaoming");
user.setAge(18);序列化
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("tempFile"));
oos.writeObject(user);反序列化
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File("tempFile")));
A1_User newUser = (A1_User) ois.readObject();

Externalizable接口

public interface Externalizable extends java.io.Serializable {void writeExternal(ObjectOutput out) throws IOException;void readExternal(ObjectInput in) throws IOException, ClassNotFoundException;
}

需要重写writeExternal()与readExternal()方法。否则所有变量的值都会变成默认值。
重写就会很灵活，可以随意加减属性

@Data
public class B1_User implements Externalizable {private String name;private int age;public void writeExternal(ObjectOutput out) throws IOException {out.writeObject(name);out.writeInt(age);}public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {name = (String) in.readObject();age = in.readInt();}
}

B1_User user = new B1_User();
user.setName("xiaoming");
user.setAge(18);ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("tempFile"));
oos.writeObject(user);ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File("tempFile")));
B1_User newUser = (B1_User) ois.readObject();

两种序列化的对比