db4o Transparent Persistence Not Working - db4o

Question

Using db4o client/server, updates are not working for collection properties of an object. I'm using transparent persistence, but that's not helping. Then, I changed my Collection property to ActivatableCollection, but no luck.
This is the server setup:
private void StartDatabase()
{
IServerConfiguration serverConfiguration = Db4oClientServer.NewServerConfiguration();
serverConfiguration.Networking.MessageRecipient = this;
serverConfiguration.Common.Add(new TransparentActivationSupport());
serverConfiguration.Common.Add(new TransparentPersistenceSupport());
string db4oDatabasePath = AppDomain.CurrentDomain.BaseDirectory;
string db4oDatabaseFileName = ConfigurationManager.AppSettings["db4oDatabaseFileName"];
int databaseServerPort = Convert.ToInt32(ConfigurationManager.AppSettings["databaseServerPort"], CultureInfo.InvariantCulture);
_db4oServer = Db4oClientServer.OpenServer(serverConfiguration, db4oDatabasePath + db4oDatabaseFileName, databaseServerPort);
string databaseUser = ConfigurationManager.AppSettings["databaseUser"];
string databasePassword = ConfigurationManager.AppSettings["databasePassword"];
_db4oServer.GrantAccess(databaseUser, databasePassword);
}
This is the entity that I want to save:
public class Application : ActivatableEntity
And this is the property within the Application entity:
public ActivatableCollection<TaskBase> Tasks { get; private set; }
This is the client code to update each object within the collection:
Application application = (from Application app in db
where app.Name == "Foo"
select app).FirstOrDefault();
foreach (TaskBase task in application.Tasks)
{
task.Description += ".";
}
db.Store(application);
Curiously, db.Commit() didn't work either.
There are two work-arounds, but I'd rather do this the "right" way.
Work-around 1: Call db.Store(task) on each task as the change is made.
Work-around 2: Before calling db.Store(), do this:
db.Ext().Configure().UpdateDepth(5);
Can anyone tell me why the list isn't updating?
If it helps, here is the ActivatableCollection class:
public class ActivatableCollection<T> : Collection<T>, IActivatable
{
[Transient]
private IActivator _activator;
/// <summary>
/// Activates the specified purpose.
/// </summary>
/// <param name="purpose">The purpose.</param>
public void Activate(ActivationPurpose purpose)
{
if (this._activator != null)
{
this._activator.Activate(purpose);
}
}
/// <summary>
/// Binds the specified activator.
/// </summary>
/// <param name="activator">The activator.</param>
public void Bind(IActivator activator)
{
if (_activator == activator) { return; }
if (activator != null && null != _activator) { throw new System.InvalidOperationException(); }
_activator = activator;
}
}

Answer 1

Indeed, transparent persistence needs a call to it's activator before every field access. However the intentions is that you do this with the enhancer-tool instead of implementing manually.
Another note: When you're using CascadeOnUpdate(true) everywhere db4o will end up storing every reachable activated object. If the object-graph is huge, this can be a major performance bottle-neck.

Answer 2

I was able to get transparent activation and persistence to work. I decided not to go with the approach for the reasons mentioned in my comment above. I think the easiest way to handle cascading updates is to simply use a client config like this:
IClientConfiguration clientConfig = Db4oClientServer.NewClientConfiguration();
And then either a bunch of these (this isn't so bad because we can add an attribute to every domain entity, then reflectively do this on each one):
clientConfig.Common.ObjectClass(typeof(Application)).CascadeOnUpdate(true);
Or this:
clientConfig.Common.UpdateDepth = 10;
return Db4oClientServer.OpenClient(clientConfig, databaseServerName, databaseServerPort, databaseUser, databasePassword);
Now, here is the server config that allowed me to get transparent persistence working.
private void StartDatabase()
{
IServerConfiguration serverConfiguration = Db4oClientServer.NewServerConfiguration();
serverConfiguration.Networking.MessageRecipient = this;
serverConfiguration.Common.Add(new TransparentActivationSupport());
serverConfiguration.Common.Add(new TransparentPersistenceSupport());
string db4oDatabasePath = AppDomain.CurrentDomain.BaseDirectory;
string db4oDatabaseFileName = ConfigurationManager.AppSettings["db4oDatabaseFileName"];
int databaseServerPort = Convert.ToInt32(ConfigurationManager.AppSettings["databaseServerPort"], CultureInfo.InvariantCulture);
_db4oServer = Db4oClientServer.OpenServer(serverConfiguration, db4oDatabasePath + db4oDatabaseFileName, databaseServerPort);
string databaseUser = ConfigurationManager.AppSettings["databaseUser"];
string databasePassword = ConfigurationManager.AppSettings["databasePassword"];
_db4oServer.GrantAccess(databaseUser, databasePassword);
}
Hope this helps someone.

Answer 3

I had the same problem with Transparent Activation and Persistence in java. I managed to get it to work cleaning the database and starting from scratch. However, no works by calling commit() after changing the object graph. You must call store() on the root object.
This is a simple example:
/*************** Item.java ******************************************/
import com.db4o.activation.ActivationPurpose;
import com.db4o.activation.Activator;
import com.db4o.collections.ActivatableSupport;
import com.db4o.ta.Activatable;
public class Item implements Activatable {
private String name;
private transient Activator activator;
public Item(String name) {
this.name = name;
}
public String getName() {
activate(ActivationPurpose.READ);
return name;
}
public void setName(String name) {
activate(ActivationPurpose.WRITE);
this.name = name;
}
#Override
public String toString() {
activate(ActivationPurpose.READ);
return "Item [name=" + name + "]";
}
public void activate(ActivationPurpose purpose) {
ActivatableSupport.activate(this.activator, purpose);
}
public void bind(Activator activator) {
this.activator = ActivatableSupport.validateForBind(this.activator, activator);
}
}
/******************* Container.java *********************************/
import java.util.Set;
import com.db4o.activation.ActivationPurpose;
import com.db4o.activation.Activator;
import com.db4o.collections.ActivatableHashSet;
import com.db4o.collections.ActivatableSupport;
import com.db4o.ta.Activatable;
public class Container implements Activatable {
private String name;
private Set<Item> items;
private transient Activator activator;
public Container() {
items = new ActivatableHashSet<Item>();
}
public String getName() {
activate(ActivationPurpose.READ);
return name;
}
public void setName(String name) {
activate(ActivationPurpose.WRITE);
this.name = name;
}
public void addItem(Item item) {
activate(ActivationPurpose.WRITE);
items.add(item);
}
public Set<Item> getItems() {
activate(ActivationPurpose.READ);
return items;
}
#Override
public String toString() {
activate(ActivationPurpose.READ);
return "Container [items=" + items + "]";
}
public void activate(ActivationPurpose purpose) {
ActivatableSupport.activate(this.activator, purpose);
}
public void bind(Activator activator) {
this.activator = ctivatableSupport.validateForBind(this.activator, activator);
}
}
/************* Main.java ********************************************/
import com.db4o.Db4oEmbedded;
import com.db4o.ObjectContainer;
import com.db4o.ObjectSet;
import com.db4o.config.EmbeddedConfiguration;
import com.db4o.ta.TransparentActivationSupport;
import com.db4o.ta.TransparentPersistenceSupport;
public class Main {
public static void main() {
EmbeddedConfiguration config = Db4oEmbedded.newConfiguration();
config.common().add(new TransparentActivationSupport());
config.common().add(new TransparentPersistenceSupport());
ObjectContainer db = Db4oEmbedded.openFile(config, System.getProperty("user.home") + "/testTP.db4o");
Container c = new Container();
c.setName("Container0");
ObjectSet<Container> result = db.queryByExample(c);
if(result.hasNext()) {
c = result.next();
System.out.println(c);
}
c.addItem(new Item("Item" + c.getItems().size()));
db.store(c);
System.out.println(c);
db.close();
}
}