Java學習之類繼承與Serializable

父類沒有實現Serializable接口時，沒有無參的構造方法，類實現了Serializable接口，這時是可以將子類序列化，但反序列化是會報錯的。

但如果父類有無參的構造方法，這時反序列化可以成功，且父類的成員變量的值為默認值，即便是子類實例化時賦值了。

當父類實現Serializable接口，此時無論寫不寫的構造方法也可以反序列化成功，且變量值為子類實例化時賦的值。

 

package serialize;

import java.io.Serializable;

public class Ser implements Serializable {
    public String ser;

//    public Ser() {
//    }

    public Ser(String ser) {
        this.ser = ser;
    }
}

 

package serialize;

import java.io.*;

public class SerializeDemo extends Ser implements Serializable {

    String serialize;

//    public SerializeDemo() {
//    }

    public SerializeDemo(String ser) {
        super(ser);
    }

    public SerializeDemo(String ser, String serialize) {
        super(ser);
        this.serialize = serialize;
    }

    @Override
    public String toString() {
        return "SerializeDemo{" +
                "serialize='" + serialize + '\'' +
                ", ser='" + ser + '\'' +
                '}';
    }

    public static void main(String[] args) {
        try {
            new ObjectOutputStream(new FileOutputStream("src//serialize//Serialize2.txt")).writeObject(new SerializeDemo("ser","Serializable"));
            SerializeDemo serializeDemo = (SerializeDemo) new ObjectInputStream(new FileInputStream("src//serialize//Serialize2.txt")).readObject();
            /**
             *java.io.InvalidClassException: serialize.SerializeDemo; no valid constructor
             *     at java.io.ObjectStreamClass$ExceptionInfo.newInvalidClassException(ObjectStreamClass.java:150)
             *     at java.io.ObjectStreamClass.checkDeserialize(ObjectStreamClass.java:790)
             *     at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2001)
             *     at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1535)
             *     at java.io.ObjectInputStream.readObject(ObjectInputStream.java:422)
             *     at serialize.SerializeDemo.main(SerializeDemo.java:32)
             *
             *     父類沒有實現Serializable接口
             */
            System.out.println(serializeDemo);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}