Deserializing Singleton

Question

    //Singleton
    public class MainList implements Serializable {
            private static MainList instance = new MainList();
            private MainList() {}

            public static MainList getInstance() {
                return instance;
            }
        }

    //Trying to deserialize..
    public MainWindow() {
        //Importing the latest version if it exists in path
        MainList mainListObj = MainList.getInstance();
        try {
            FileInputStream fis = new FileInputStream(path);
            ObjectInputStream oin = new ObjectInputStream(fis);
            mainListObj = (MainList) oin.readObject(); //HERE//////
        }
        catch (Exception exc) {
            return;
        }
    }

Singleton-Object of class MainList is serialized & can be found by path.

On the line //HERE/// object successfully deserializing to mainListObj, BUT it's local..

How can I make it global? I think it could be solved by chanching getInstance method..somehow..

If you can deserialize and replace the instance then it's **not** a singleton. Therefore the answer is "_you cannot deserialize a singleton_". — Boris the Spider, Mar 18 '18 at 10:58
I don't want to replace it, I want to create a new one(first one), using the obj I deserialized.. — Nick Kulese, Mar 18 '18 at 11:07
You need to understand what "Java passes references by value" means before you can solve this problem. All you've done in your code is reassigned a reference. Also: you may want to investigate how to close external resources. — Boris the Spider, Mar 18 '18 at 11:44

score 0 · Answer 1 · answered Mar 21 '18 at 06:06

0

Your case is not singleton.

In your case, you can simply provide a setter.

static void setInstance(MainList newInstance) {
 instance = newInstance;
}

MainList.setInstance(mainListObj);

answered Mar 21 '18 at 06:06

Dean Xu

4,438
1
17
44

Deserializing Singleton

1 Answers1