Doubt on Serialization?

[Ashok Pradhan]

My program is compiles but throws the following exception at runtime:-
java.io.NotActiveException: not in call to writeObject
at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:413)
at Test.writeObject(Test.java:10)
at Test.main(Test.java:23)

please explain me why it throws NotActiveException,I am confused....

import java.io.*;
class Test implements Serializable
{
Cat c = new Cat();
transient Dog d = new Dog();
private  void writeObject(ObjectOutputStream os)
{
try
{
os.defaultWriteObject();
os.writeInt(d.getDogLegs());
}
catch(Exception ex)
{
ex.printStackTrace();
}
}
public static void main(String[] args)
{
try
{
ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream("ser.tx"));
new Test().writeObject(os);
}
catch(Exception ex)
{
ex.printStackTrace();
}
 
}
}
class Cat implements Serializable
{
int legs=10;
public void go()
{
System.out.println("Cat.........");
}
}
class Dog
{
private int doglegs =1000;
 
public int getDogLegs()
{
return doglegs;
}
}

[ August 10, 2008: Message edited by: Ashok Pradhan ]

[ August 10, 2008: Message edited by: Ashok Pradhan ]
[ August 10, 2008: Message edited by: Ashok Pradhan ]

[Ulf Dittmer]

The javadocs of the defaultWriteObject method explain why you're getting this exception - you're not serializing the current object.

I think what you may mean to call is "os.writeObject(new Test())". Then you need to implement the writeObject method as explained in the javadocs for Serializable.

[Ashok Pradhan]

In my program the class Dog does not implements Serializable interface:-

class Dog
{
private int doglegs =1000;
 
public int getDogLegs()
{
return doglegs;
}
}

but I want manually write doglegs by serialization as well as all the members of Test class(e.g Cat c=new Cat()) :-

transient Dog d = new Dog();
private  void writeObject(ObjectOutputStream os)
{
try
{
os.defaultWriteObject();
os.writeInt(d.getDogLegs());
}
catch(Exception ex)
{
ex.printStackTrace();
}
}

but how can I invoke the writeObject() it throws NotActiveException and what are the changes needed to fulfill my program's requirement.

[Henry Wong]

but how can I invoke the writeObject() it throws NotActiveException and what are the changes needed to fulfill my program's requirement.

Basically, you are *not* supposed to call the writeObject() method directly. It is a method used to support Serialization. See Ulf explanation on how to serialize an object. The serialization will indirectly call the writeObject() method.

Henry

[Ashok Pradhan]

Now I got it.invoking readObject(ObjectOutputStream os) directly is the wrong process and it is automatically called in the serialization process.am I correct !!!.and my program now compiles and run successfully..

import java.io.*;
class Test implements Serializable
{
Cat c = new Cat();
transient Dog d = new Dog();
private  void writeObject(ObjectOutputStream os)
{
try
{
os.defaultWriteObject();
os.writeInt(d.getDogLegs());
}
catch(Exception ex)
{
ex.printStackTrace();
}
}
public static void main(String[] args)
{
Test t = new Test();
try
{
ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream("ser.tx"));
[B]os.writeObject(t);[/B]
}
catch(Exception ex)
{
ex.printStackTrace();
}
 
}
}
class Cat implements Serializable
{
int legs=10;
public void go()
{
System.out.println("Cat.........");
}
}
class Dog
{
private int doglegs =1000;
 
public int getDogLegs()
{
return doglegs;
}
}
 
 

Thanks Ulf Dittmer and Henry !!!
[ August 10, 2008: Message edited by: Ashok Pradhan ]