java 如何序列化接口？
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How can I serialize an interface?
提问by Jeff Axelrod
Suppose I have a Serializableclass ShapeHolderthat owns an object that implements a SerializableShapeinterface. I want to make sure the correct concrete shape object is saved (and the correct type is later restored).
假设我有一个拥有实现接口的对象的Serializable类。我想确保保存了正确的具体形状对象（并且稍后恢复了正确的类型）。ShapeHolderSerializableShape
How can I accomplish this?
我怎样才能做到这一点？
interface Shape extends Serializable {}
class Circle implements Shape {
private static final long serialVersionUID = -1306760703066967345L;
}
class ShapeHolder implements Serializable {
private static final long serialVersionUID = 1952358793540268673L;
public Shape shape;
}
采纳答案by Jeff Axelrod
Java's Serializabledoes this for you automatically.
JavaSerializable会自动为您执行此操作。
public class SerializeInterfaceExample {
interface Shape extends Serializable {}
static class Circle implements Shape {
private static final long serialVersionUID = -1306760703066967345L;
}
static class ShapeHolder implements Serializable {
private static final long serialVersionUID = 1952358793540268673L;
public Shape shape;
}
@Test public void canSerializeShape()
throws FileNotFoundException, IOException, ClassNotFoundException {
ShapeHolder circleHolder = new ShapeHolder();
circleHolder.shape = new Circle();
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("test"));
out.writeObject(circleHolder);
out.close();
ObjectInputStream in = new ObjectInputStream(new FileInputStream("test"));
final ShapeHolder restoredCircleHolder = (ShapeHolder) in.readObject();
assertThat(restoredCircleHolder.shape, instanceOf(Circle.class));
in.close();
}
}
回答by Esko Luontola
I want to make sure the correct concrete shape object is saved (and the correct type is later restored).
我想确保保存了正确的具体形状对象（并且稍后恢复了正确的类型）。
Java's default serialization (ObjectInputStream & ObjectOutputStream) does that out-of-the-box. When serializing, Java writes there the name of the concrete class and then uses in when deserializing.
Java 的默认序列化（ObjectInputStream 和 ObjectOutputStream）是开箱即用的。序列化时，Java 在那里写入具体类的名称，然后在反序列化时使用 in。
回答by Alexeyy Alexeyy
import java.io.*;
public class ExampleSerializableClass implements Serializable {
private static final long serialVersionUID = 0L;
transient private Shape shape;
private String shapeClassName;
private void writeObject(ObjectOutputStream out) throws IOException {
shapeClassName = shape.getClass().getCanonicalName();
out.defaultWriteObject();
}
private void readObject(ObjectInputStream in)
throws IOException, ClassNotFoundException,
InstantiationException, IllegalAccessException {
in.defaultReadObject();
Class<?> cls = Class.forName(shapeClassName);
shape = (Shape) cls.newInstance();
}
}
