db4o « Database Product « Java Database Q&A

1. db4o experiences?    stackoverflow.com

I'm currently trying out db4o (the java version) and I pretty much like what I see. But I cannot help wondering how it does perform in a real live (web-)environment. Does ...

2. db4o and OSGi - empty database after restart    stackoverflow.com

I'm using db4o 6.4.54 in OSGi environment as a model storage. Every time I restart OSGi framework, the database appears to be empty, although the file is there and not empty ...

3. How to disable Java security manager?    stackoverflow.com

Is there any way to completely disable Java security manager?
I'm experimenting with source code of db4o. It uses reflection to persist objects and it seems that security manager doesn't allow ...

4. How does db4o instantiate objects?    stackoverflow.com

What mechanism does db4o use to instatniate stored objects ? My class isn't Serializable and doesn't provide zero argument constructor and the only constructor throws NullPointerException when it's argument is null. In spite ...

5. db4o to preserve identity of objects    stackoverflow.com

Is there a way to preserve an objest identity in db4o. Suppose I store a BigDecimal in embedded db4o. When I read it twice I get two distict objects with the same value ...

6. Can/should I use WeakReference in my complex object structure with db4o?    stackoverflow.com

I'm considering to port an application to db4o. The data model consists of lots of small objects with a lot of references between each other. For example, I have a book ...

7. Caching big children in data model with db4o    stackoverflow.com

I have a data model with a skeleton (metadata) and large data objects. I'd like to keep the skeleton in memory and hold weak references to the data objects. I understand ...

8. Handling data maintenance in Object Databases like db4o    stackoverflow.com

One thing I have continually found very confusing about using an object database like db4o is how you are supposed to handle complex migrations that would normally be handled ...

9. Is db4o object manager enterprise free? Where can I download it? Is it a standalone application?    stackoverflow.com

As per the title I have three parts to this question... Is db4o object manager enterprise free?
-I saw a blog post about it being free. Where can I download it? -the website is rather ...

10. How to use an OSGi service from a web application?    stackoverflow.com

I'm trying to develop a web application that is going to be launched from a HTTP OSGi service, this application needs to use other OSGi service (db4o OSGi), for what ...

11. How to use the distinct on databases DB4O in Java?    stackoverflow.com

Who can tell me how to use Distinct operation on db4o in Java code. I couldn't find any example in Java. Thanks!

12. Is there a tool that will create Java or .NET classes from a db4o database file?    stackoverflow.com

I have a db4o database file. Is there a tool that will generate Java or .NET classes (source) from this database?

13. db4o viewer - Java / Linux    stackoverflow.com

I need a db4o viewer for a Linux box running Java. I noticed this post was for a .net client, but I don't have Windows and don't intend to. Is there ...

14. Best practise for adding a bidirectional relation in OO model    stackoverflow.com

I'm struggling to come up with a good way of adding a bidirectional relation in OO model. Let's say there is a Customer who can place many Orders, that is to ...

15. ClassCastException in DataNucleus DAO object when persisting/retreiving an Object using JDO    stackoverflow.com

I've created a simple webapp using Spring & Jetty, and am creating a hello world JDO test using DataNucleus & DB4O. I can persist a class no problem, but when I go ...

16. JDO not retrieving/persisting a collection    stackoverflow.com

I have the following data model class defined:

@PersistenceCapable
public class TestSerializableModelObj {
    @Persistent(serialized="true", defaultFetchGroup="true")
    private MyPOJO myField;

    @Persistent(serialized="true", defaultFetchGroup="true")
    private ...

17. JDO: Is the PersistenceManager a singleton?    stackoverflow.com

Just the basics: I'm using DataNucleus backed with an embedded DB4O database. If I do this simple test:

    PersistenceManager pm1 = persistenceManagerFactory.getPersistenceManager();
    PersistenceManager pm2 = persistenceManagerFactory.getPersistenceManager();

 ...

18. Serializable[] attribute in Object not stored in db4o    stackoverflow.com

I ran in a strange behavior of db4o. When I persist an Object (implementing Serializable) with an attribute of Serializable[], the Array is only returned once from the store correctly then ...

19. db4o - count number of total records in database?    stackoverflow.com

I am using db4o and was wondering, how can I get the total number of objects in the database? There isn't an explicit way using the API; however, I can ...

20. DB4o HashMap toString()    stackoverflow.com

As a learning tool for DB4o and Java I have started to create a Telephone Directory. To do this I create an instance of a TelephoneDirectory which contains a year and ...

21. Db4o is extremely slow in Eclipse debug mode    stackoverflow.com

I'm working with a db4o database and have a database of approximately 1000-5000 objects on Mac OS X, developing in Eclipse Helios. Currently, I'm retrieving all objects of a certain class:

ObjectSet<Task> query ...

22. hierarchical nested data structure in db4o (or any other oodb)    stackoverflow.com

Really my question is, if I were to use a nested data structure in oodb would I be placing instance of classes within other instances in the db, or is there ...

23. db4o - DatabaseClosedException    stackoverflow.com

I am trying to store an entity with db4o through an arquillian test case and am getting a DatabaseClosedException:

Test set: com.walterjwhite.address.api.datastore.TestAddressDatastore

24. com.db4o.ext.DatabaseClosedException    stackoverflow.com

I'm working with db4o embedded for Java (JSE6) running a Servlet app under Tomcat. Lately I started getting weird exceptions. When trying to save a new object to the DB I get ...

25. db4o: Same class, different java projects    stackoverflow.com

I have two different Java Applications A and B. They should use the same Database for user management (If the User has an account in Application A, he also has an ...

26. Store a list of objects in db4o    stackoverflow.com

I wonder if there's a more beautiful way to store a list of objects then:

ArrayList<Item> itemsList = new ArrayList<Item>;
itemsList.add(new Item(1));
itemsList.add(new Item(2));

ItemDBProvider dbProvider = new ItemDBProvider();

for (int i = 0; i < ...

27. db4o : ActivationDepth seems to have no effect (?)    stackoverflow.com

Can someone please explain to me why setting the Activation Depth seems to have no effect in the code-sample below ? This sample creates 'Block'-objects which all have a number and a child-block. Since the ActivationDepth ...

28. DB4O performance retrieving a large number of objects    stackoverflow.com

I'm interesting in using DB4O to store the training data for a learning algorithm. This will consist of (potentially) hundreds of millions of objects. Each object is on average ...

29. Java: can db4o store org.w3c.dom.Node?    stackoverflow.com

Is it possible to store org.w3c.dom.Node and org.w3c.dom.NodeList as well?

public DocumentElement {
private String name;
private Node thisNode;
private NodeList thisList;
}

30. db4o: set and get method not available?    stackoverflow.com

ObjectContainer db=Db4o.openFile(Util.DB4OFILENAME);
db.get(); //doesn't exist

31. Problem with Eclipse and Db4o    java-forums.org

32. Storing objects directly with db4o    java-forums.org

33. DB4o HashMap toString()    java-forums.org

I'm not really familiar with databases, however; it seems that you are printing a telephone directory, if you can get access to the map you can find the name of the person in the map, correct? I apologize if I am being a bit unclear. You gave yourself the ability to access the year and map in the directory, your result.next ...

34. need help in compiling a object database (DB4O) program    forums.oracle.com

i know i am not good at programming, but i am trying to learn, but also have to submit some projects , that's why i have ask in forums, because there is no body to help me, i am stuck at this error since from last 2 hrs, so dont want to waste more time, that's why i posted it forum, ...