如何在标准序列化中序列化非序列化基类？ [英] How to serialize non-serializable base class in standard serialization?

问题描述

我无法控制基类的源代码，那么，如何在子类上使用标准序列化？

I can't control the source code of the base class, then, how can I use standard serialization on the subclass?

在本例中，字段 a 根本没有序列化，但B是可序列化的：

In this example, field a is not serialized at all, though B is serializable:

// a.jar

class A {
    int a;
}

// b.jar

class B
        extends A
        implements Serializable {
    int b;
}

public class HelloWorldApp {

    public static void main(String[] args)
            throws Exception {
        B b = new B();
        b.a = 10;
        b.b = 20;

        ByteArrayOutputStream buf = new ByteArrayOutputStream();

        ObjectOutputStream out = new ObjectOutputStream(buf);
        out.writeObject(b);
        out.close();

        byte[] bytes = buf.toByteArray();
        ByteArrayInputStream _in = new ByteArrayInputStream(bytes);
        ObjectInputStream in = new ObjectInputStream(_in);
        B x = (B) in.readObject();
        System.out.println(x.a);
        System.out.println(x.b);
    }

}

输出：

0
20

推荐答案

你不能！

字段 a 不会被序列化！

解决方法：实现自定义序列化。您应该实现 Externalizable 接口和 writeExternal，readExternal 方法。
在thess方法中，您可以写入和读取 a 字段的值。

You can't!
field a will not be serialized!
Work around: implement your custom serialization. You should implement Externalizable interface and writeExternal, readExternal methods. In thess methods you can write and read value of your a field.

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