What happens when a Serializable object is created via Singleton Pattern?
java, object, serializable, singleton
Solution
Unfortunately, what happens by default is you get a second (or third, or thirty-seventh) instance of your singleton -- not good. Luckily there's a way around this: by implementing the readResolve() method, which can return a replacement object -- the proper singleton object, in your case -- instead of the one returned by default serialization. The link describes the particulars, but it's pretty simple -- you just implement this parameterless instance method to return the singleton object.
Problem
Question says everything. Is there any special event occurs? I have a class which needs to implement Serializable interface. I am developing an application using Wicket. I have implemented a Factory class which will provide some links (to remove the redundancy of same code block written over and over): ``` public class NavigationLinkFactory implements Serializable { private static final long serialVersionUID = 7836960726965363785L; private NavigationLinkFactory() { } private static class SingletonHolder { public static final NavigationLinkFactory instance = new NavigationLinkFactory(); } public static NavigationLinkFactory getFactory() { return SingletonHolder.instance; } private Object readResolve() throws ObjectStreamException { return SingletonHolder.instance; } public Link<Serializable> getUserHomeLink() { return new Link<Serializable>("home", new Model<Serializable>()) { private static final long serialVersionUID = -8282608926361995521L; @Override public void onClick() { EMSSession session = (EMSSession) getSession(); session.setActiveHorizonalMenu(1); setResponsePage(HomePage.class); } }; } public Link<Serializable> getProfileLink() { return getProfileViewLink(); } public Link<Serializable> getProfileViewLink() { return new Link<Serializable>("profileView", new Model<Serializable>()) { private static final long serialVersionUID = 232185489384306999L; @Override public void onClick() { EMSSession session = (EMSSession) getSession(); session.setActiveHorizonalMenu(2); setResponsePage(ProfileViewPage.class); } }; } } ``` If I doesn't implement Serializable then I am getting exception at `java.io.ObjectOutputStream.writeObject`, which is thrown by the runtime environment of the wicket framework. If I implement it then it is gone. So what really happens when one calls `ObjectInputStream#readobject()` method for some object created by Singleton pattern? I am not adding wicket tag because I don't think this question is related to the Wicket.