不可序列化父类的可序列化子类

Question

我在android / java中对Location的子类进行序列化遇到了麻烦

位置不可序列化。我有一个名为FALocation的第一个子类，它没有任何实例变量。我已经宣布它可序列化。

然后，我有一个名为Waypoint的第二个类，看起来像这样：

public class Waypoint extends FALocation implements Serializable {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    /* Class variables *******************************************************/
    private static int CLASS_VERSION=1; //Used to version parcels

    /* Instance variables ****************************************************/
    private transient String type=DataHelper.PT_TYPE_US;
    private transient String country; 
    private transient String name=null;
    private transient String description=null;
    private transient int elevation = 0;
    private transient int population = 0; // Afterthought, added to match the DB structure

    /* Constructors **********************************************************/    
    public Waypoint() {
        super();
    }

    public Waypoint(double lat, double lon, String name, String description) {
        super(lat, lon);
        this.setName(name);
        this.setDescription(description);
    }

    public Waypoint(Location l) {
        super(l);
    }

    public Waypoint(String provider) {
        super(provider);
    }


    /* Implementing serializable */
    private void writeObject(java.io.ObjectOutputStream out) throws IOException {
        Log.v("DroidFA", "Serialising \"%s\" (v%d).", Waypoint.class.getSimpleName(), CLASS_VERSION);
        out.writeInt(CLASS_VERSION);

        out.writeObject(type);
        out.writeObject(country);
        out.writeObject(name);
        out.writeObject(description);
        out.writeInt(elevation);
        out.writeInt(population);
    }

    private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException {

        int serialClassVersion = in.readInt();
        Log.v("DroidFA", "Deserialising \"%s\" (v%d).", Waypoint.class.getSimpleName(),serialClassVersion);

        type = (String) in.readObject();
        country = (String) in.readObject();
        name = (String) in.readObject();
        description = (String) in.readObject();
        elevation = in.readInt();
        population = in.readInt();
    }
}

序列化工作正常。

反序列化会产生跟随翼异常（腿对象包含一个航路点）：

10-05 13:50:35.259: WARN/System.err(7867): java.io.InvalidClassException: android.location.Location; IllegalAccessException
10-05 13:50:35.267: WARN/System.err(7867):     at java.io.ObjectInputStream.resolveConstructorClass(ObjectInputStream.java:2010)
10-05 13:50:35.267: WARN/System.err(7867):     at java.io.ObjectInputStream.readNewObject(ObjectInputStream.java:2095)
10-05 13:50:35.267: WARN/System.err(7867):     at java.io.ObjectInputStream.readNonPrimitiveContent(ObjectInputStream.java:929)
10-05 13:50:35.267: WARN/System.err(7867):     at java.io.ObjectInputStream.readObject(ObjectInputStream.java:2285)
10-05 13:50:35.278: WARN/System.err(7867):     at java.io.ObjectInputStream.readObject(ObjectInputStream.java:2240)
10-05 13:50:35.278: WARN/System.err(7867):     at com.droidfa.navigation.Leg.readObject(Leg.java:262)
.../...

Answer 1

序列化位置绝对必要吗？也许您可以将其标记为瞬态，并在反序列化对象后动态获取它。（无论如何，从文档开始）：

问：如果A类没有实现Serializable，但是子类B实现了Serializable，那么在B进行序列化时，是否会对A类的字段进行序列化？

答：仅可序列化对象的字段被写出并还原。仅当对象具有可初始化不可序列化超类型的字段的无参数构造函数时，才可以还原该对象。如果子类可以访问超类的状态，则可以实现writeObject和readObject来保存和恢复该状态。

因此，如果子类可以访问其不可序列化的超类的字段，则可以使用writeObject和readObject协议来实现序列化。否则，将存在无法序列化的字段。