db4o Developer Community

good morning, I have an interface IMorning : public interface IMorning { enum Mood {GOOD,BAD};   Mood getMood(); }    And I have the class Morning   public class Morning implements IMorning, Serializable { private static final long serialVersionUID = 5386061933351709956L;  private Mood mood;  Mood ...

I was going thru some of this stuff, but I'd found no answer for auto-increment on db4o-tutorial, so here's what I came up with, I'd really enjoy if you guys would give your points of view about it... Simple OO stuff, let's make a SuperEntity abstract class..I'm using C# for it.  using Db4o; public abstract class SuperEntity { } ...

Actually I think the decision is quite easy and it has been taken a long time ago for db4o. The Java Language Specification is explicit what the *same* object is:object1 == object2 We never store *the same* object twice in a database. What you are asking for is special treatment for objects that are *equivalent*.object1.equals(object2) The ...

This is a repost from the user forum: When you store a graph of objects to db4o and retrieve it afterwards, db4o assembles the graph in exactly the same way as it was stored. In doing so db4o makes sure that every object is instantiated only once, no matter which access path you choose. You can run hundreds of queries, navigate through hundreds ...

WolfBenz: What could be greater and more natural, for an Object Database, than that Objects themselves could define their equality? Well, that's exactly what equals() does. :-) Hi Wolf, we have had many discussions about this theme in the past. Let me explain why db4o behaves as it does. When you store a graph of objects to db4o and ...

I am newbie in db4o, programming C# and db4o version 7.1 with transparent persistency by code instrumentation (db4otool –tp –nq). Could you help me to better understand object identity issues?I have a server-client scenario. The client creates an object, stores it in the server and closes the OC. Then in two parallel threads I open two separate ...

i'd like to use UniqueFieldValueConstraint to check object uniqueness in project. But i need to check identity of some objects by 2 fields. For example: configuration.objectClass(Pilot.class).objectField(''name'').indexed(true); configuration.objectClass(Pilot.class).objectField(''points'').indexed(true); configuration.add(new ...

I've a problem with the database file size limitation (254 GB). Yes it is quite big however depending of nature of the stored objects (images, sound, etc) this can pose a problem. What's come in mind in this case is to use multiple ObjectContainers; but what happens if stored objects in one container must reference objects in another container ...

Hi.  I am using GWT to make a simple web application. The initial simplicity of db4o was really impressive and compelling. But I have one problem now: I'd really like to define my object model only one place, using no annotations or exotic (at least to the client side of GWT) classes. But when previously stored objects are serialized to the ...

Hello! Can somebody tell me how SODA behaves for querying Lists? Assumed that Foo is a class which got a field (List _bars) which holds Bar-Objects and I want to get all Foos which got a special Bar. Does this Query Query q = _objectContainer.query();q.constrain(Foo.class);q.descend(''_bars'').constrain(special_bar); // special_bar is a ...