CODEWITHSUNDEEP
javaserialization
Geek
Geek

Reputation: 27203

What will be the impact if there is a non serializable field in a Serializable class?

I am doing some code review and came across serializable class that contains a non serializable field. That field is neither declared as transient. Can this kind of code be termed as a code smell. If yes then why?

public class A implements Serializable{

 private B field ; // B is non serializable

}

Upvotes: 1

Views: 488

Answers (4)

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 136042

It's not the field but the object this field points to may cause NotSerializableException. E.g. if field is null there will be no exception. Or if field points to an instance of C which is a Serializable subclass of B there will be no exception.

Upvotes: 0

Thilo
Thilo

Reputation: 262584

This will make an exception when you try to serialize the object (unless the field is null, or the actual object is of a serializable subclass of B).

You have to make it either transient or serializable (or implement your own serialization method).

Upvotes: 1

shazin
shazin

Reputation: 21883

This will result in an error if you try to serialize A. Because B is not Serializable. It is code smell.

Upvotes: -1

Jon Skeet
Jon Skeet

Reputation: 1501133

It will throw an exception when you try to serialize it, if the execution time type of the object isn't serializable.

For example, this does serialize:

import java.io.*;

public class Test implements Serializable {
    private Object object;

    public static void main(String[] args) throws Exception {
        Test test = new Test();
        test.object = "";
        // Now serialize test
    }
}

That will create an appropriate file - but if test.object is set to new Object() instead, then it will throw the exception.

It's not just a code smell - it's a bug, unless B is an abstract class and all concrete subclasses are serializable... or if you know some other way that it will never be serialized unless the value of field is serializable or null.

Upvotes: 5

Related Questions