Programming language: Java
Tags: Database    
Latest version: v8.1.9

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The Basic Principle of db4o

db4o is a non-intrusive persistence system that stores any complex object with one single line of code. The class schema of your application classes is analysed and adjusted in real time when objects are stored. Object-oriented querying functionality is provided through Native Queries (NQ), the ability to query the database using .NET syntax and semantics (similar in concept to LINQ/DLINQ), Query by Example (QBE) which uses prototype objects for querying and other APIs. High performance is achieved with indexed fields and by reducing database-file-internal redirections to the absolute minimum. db4o features ACID transactions, fast embedded single-user mode and multi-transactional Client/Server access, locally and through TCP, object-oriented replication, and the ObjectManager to browse database files.

Download Object Manager Binaries to TRY

Db4o-GPL .NetStandard2.0 & Java7+ Version

Not as complexity as big SQL database server, not as simplicity as iBoxDB,

Db4o is the best database project to help you to learn how to write a database.

This adventurous oop-database project, has no news in a long time. here update it to .NetStandard2 & Java7. some users maybe need it.

DotNet Core

Use MonoDevelop to Open Db4o-2010.sln or run

Db4objects.Db4o.Optional/dotnet publish -c Release
test/dotnet run

/test includes a dotnet core example.


Use IDE NetBeans 11 to Open db4o.j/db4o-core project

 Build Project will output a jar to ../db4o-gpl/db4o.j/db4o-core/dist/db4o-core.jar
 or Run File, db4o.j/db4o-core/tutorial/src/com/db4odoc/f1/Main.java 


Db4o-Projects/*/dotnet publish -c Release //like above
Add 4 DLLs in /Output to xamarin-project

var path = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
string dbpath = Path.Combine(path, "x.db");
db = Db4oEmbedded.OpenFile(dbpath);

Project Properities->Android Options->Linking->"Sdk Assemblies Only" (not "Sdk and User Assemblies").
Permission: Read/Write_External_Storage, INTERNET

Android Java

// <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
// <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
// <uses-permission android:name="android.permission.INTERNET"/>

private class Async extends android.os.AsyncTask{
  protected Object doInBackground(Object... arg) {
    //      + "/data/" + "com.example.fapp" + ""
    //DB4O Code here 
    return null;

new Async().execute(null);

Download Assemblies Directly



Nuget db4o-core

.NET Tutorials

Getting Started With db4o


Object-oriented database programming with db4o


.NET Docs Db4oEmbedded
JAVA Docs Db4oEmbedded
About UpdateDepth


.NET Example
JAVA Example


One Local Share Connection

ObjectContainer db = Db4oEmbedded.openFile(Db4oEmbedded
                .newConfiguration(), DB4OFILENAME);

See Session Object Container

Multiple Local Connections

ServerConfiguration config = Db4oClientServer.newServerConfiguration();
//Set Port = 0
ObjectServer server = Db4oClientServer.openServer(config, DB4OFILENAME, 0);
try {
  ObjectContainer client = server.openClient();
  // Do something with this clients
} finally {
//Open new Client for every request. Concurrent
public static void queryLocalServer(ObjectServer server) {
  ObjectContainer client = server.openClient();
  listResult(client.queryByExample(new Car("885588")));

Multiple Remote Connections

//set PORT > 0
ObjectServer server = Db4oClientServer.openServer(Db4oClientServer
                .newServerConfiguration(), DB4OFILENAME, PORT);
server.grantAccess(USER, PASSWORD);
try {
  ObjectContainer client = Db4oClientServer.openClient(
    Db4oClientServer.newClientConfiguration(), "localhost",PORT, USER, PASSWORD);
  // Do something with this client, or open more clients
} finally {

Java Lambda Index

var rs = see.query((Record r) -> r.indexField == dv);

Lambda index. FieldName on the left, enable index; on the right, disable index.

Getting Started

public class Node
  public String Name;
  public Node Left;
  public Node Right;

StringBuilder sb = new StringBuilder();
var path = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
path = Path.Combine(path, "t.db");

var cf = Db4oEmbedded.NewConfiguration();
cf.Common.Add(new TransparentActivationSupport());
cf.Common.Add(new TransparentPersistenceSupport());
using (var oc = Db4oEmbedded.OpenFile(cf, path))
    using (var ss = oc.Ext().OpenSession())
        Node root = new Node();
        root.Name = "Root";
        root.Left = new Node();
        root.Left.Name = "LEFT";
        root.Left.Left = new Node();
        root.Left.Left.Name = "LEFT.LEFT";
    using (var ss = oc.Ext().OpenSession())
        sb.AppendLine(ss.QueryByExample(new Node { Name = "Root" }).First().Left.Left.Name);

Object Management

Use NetBeans-11 with Java on Linux

build 'db4o.j/db4o-core' project, get db4o-core.jar
use NetBeans open db4o-gpl/admins/om.j/ObjectManager/ 
build and run

Use MonoDevelop-7.8.4+ with Mono-6 on Linux

Db4o-Projects/*/dotnet publish -c Release, get db4o DLLs
use MonoDevelop open  db4o-gpl/admins/om.net/OMAddin-2010.sln 
build and run

See the result, images/db4o_gpl.png

See the result, images/db4o_java_gpl.png

License: GPL , as MySQL.

The info from the author. http://supportservices.actian.com/versant/default.html


With regret we have to announce that Actian decided not to actively pursue and promote the commercial db4o product offering for new customers any longer.

Since the db4o dual licensing model allows for the free usage of the community edition of db4o for non-commercial purposes, 
you have the opportunity to continue to use it for your non-commercial applications or
even fork it to provide support for the community.
You can find the latest installer packages including the source tarball here for Java, .NET35, .NET40

Actian will continue to provide commercial licenses and support for existing customers with active support contract.

*Note that all licence references and agreements mentioned in the Db4o-gpl README section above are relevant to that project's source code only.