Does Java Serialization work for cyclic references?

Question

For example: Object A contains Object B that contains Object C that contains Object A.

Will Object A serialize properly?

Comment #9 here indicates that it does not work .

In contrast, XStream indicates that it does handle cyclic references.

Answer 1

Yes, the default Java serialization works for cyclic references. When you serialize object C, the field will contain a backreference to the already-serialized object A instead of serializing it again.

Answer 2

Yes, Java serialization works for circular references, read here for more information to help your understanding of what Java serialization can do.

Answer 3

Yes it does.

I did this very, very, simple test, and at least it finish the serialization. I assume it is correct, but you can check that with some extra lines.

import java.io.*;
class A implements Serializable { B b; }
class B implements Serializable { C c; }
class C implements Serializable { A a; }
class Test {
    public static void main( String [] args ) throws IOException {
        A a = new A();
        a.b = new B();
        a.b.c = new C();
        a.b.c.a = a;
        new ObjectOutputStream( new ByteArrayOutputStream( ) ).writeObject( a );
        System.out.println("It works");

    }    
}

Answer 4

You can actually view the referencing firsthand if you serialize your object to XML. The child objects are only serialized once. Any reference (anywhere in the serialized structure) to a child object that has already been serialized will simply point to that object in the file.

Serializing cyclic references can get a little messy, though, so you might want to avoid them if you can.