serializable interface

[S Majumder]

Serializable interface is a "marker" interface .We know that marker interface has method , but when we impliment the serializable interface we use the readObject and writeObject methods.So from where these methods come ?

Thanks,
S

[Shanky Sohar]

The writeObject and ReadObject are the part of ObjectOutputStream class

[Shanky Sohar]

s begri wrote:We know that marker interface has method

No the marker interface doesn't contains any methods

[Rob Spoor]

Shanky Sohar wrote:The writeObject and ReadObject are the part of ObjectOutputStream class

These are also private methods that a serializable class can optionally implement to have a bit more control over their serialization / deserialization.

s beqri, these methods are just there, as part of the serialization mechanism specification. They aren't defined by any interface or base class. They get special treatment because Sun said they should.

[S Majumder]

Thank you all
If the serializable interface has no method at all , so why should we implement it when we try to serialize an object ? We can use only the ObjectOutputStream class.

regards,
S

[Shanky Sohar]

Rob Spoor wrote:

Shanky Sohar wrote:The writeObject and ReadObject are the part of ObjectOutputStream class

These are also private methods that a serializable class can optionally implement to have a bit more control over their serialization / deserialization.

Yes you are right,but the methods are the part of ObjectOutputStream class,we are implementing them just to have a little more control over the serialization or deserilization.These methods are not within the serialization interface.
Please correct me if i am wrong

[Mike Simmons]

Shanky Sohar wrote:Yes you are right,but the methods are the part of ObjectOutputStream class,we are implementing them just to have a little more control over the serialization or deserilization.These methods are not within the serialization interface.
Please correct me if i am wrong

We are NOT implementing the methods in ObjectOutputStream and ObjectInputStream. Those are different methods, with different signatures.

Method in ObjectOutputStream:

public final void writeObject(Object obj) throws IOException

Method in ObjectInputStream:

public final Object readObject() throws IOException, ClassNotFoundException

Optional methods in the object to be serialized:

private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException;
private void writeObject(ObjectOutputStream stream) throws IOException
private void readObjectNoData() throws ObjectStreamException;

Not the same methods. Same names, but different arguments, different classes, not inherited, overridden, or overloaded.

[Shanky Sohar]

Oops...

got it.

[S Majumder]

Thanks again ,
actually am little confused then what actually this marker interface is doing ?


regards,
S

[Wouter Oet]

It is just to inform the serialization process that that kind of object is serializable. The decision was made that not all objects can be serialized but only if the developer declares so.

So you can do something like

if(object instanceof Serializable) {
   // serialize
} else {
   throw new RuntimeException("Not serializable");
}