Java 如何解决UniqueFieldConstraintViolationException db4o

代码运行正常，但给我一个我无法控制的异常，这是控制台消息：

The person with this DNI es already exists
Exception in thread "main" com.db4o.constraints.UniqueFieldValueConstraintViolationException: class: Vehiculo field: matricula
    at com.db4o.constraints.UniqueFieldValueConstraint$1.ensureSingleOccurence(UniqueFieldValueConstraint.java:66)
    at com.db4o.constraints.UniqueFieldValueConstraint$1.onEvent(UniqueFieldValueConstraint.java:97)
    at com.db4o.internal.events.Event4Impl.trigger(Event4Impl.java:78)
    at com.db4o.internal.events.EventRegistryImpl$4.run(EventRegistryImpl.java:123)
    at com.db4o.foundation.DynamicVariable.with(DynamicVariable.java:54)
    at com.db4o.internal.InCallback.run(InCallback.java:24)
    at com.db4o.internal.events.EventRegistryImpl.withExceptionHandlingInCallback(EventRegistryImpl.java:279)
    at com.db4o.internal.events.EventRegistryImpl.commitOnStarted(EventRegistryImpl.java:121)
    at com.db4o.internal.LocalTransaction.dispatchCommittingCallback(LocalTransaction.java:89)
    at com.db4o.internal.LocalTransaction.commit(LocalTransaction.java:66)
    at com.db4o.internal.LocalTransaction.commit(LocalTransaction.java:59)
    at com.db4o.internal.LocalObjectContainer.commitTransaction(LocalObjectContainer.java:689)
    at com.db4o.internal.LocalObjectContainer.close2(LocalObjectContainer.java:94)
    at com.db4o.internal.ObjectContainerBase.close1(ObjectContainerBase.java:361)
    at com.db4o.internal.ObjectContainerBase.close(ObjectContainerBase.java:344)
    at Principal.main(Principal.java:38)


import com.db4o.Db4oEmbedded;
import com.db4o.ObjectContainer;
import com.db4o.ObjectSet;
import com.db4o.config.EmbeddedConfiguration;
import com.db4o.constraints.UniqueFieldValueConstraint;
import com.db4o.constraints.UniqueFieldValueConstraintViolationException;
import com.db4o.query.Query;


public class Principal {

    public static void main(String[] args) {

        EmbeddedConfiguration config = Db4oEmbedded.newConfiguration();
        config.common().objectClass(Persona.class).objectField("dni").indexed(true);
        config.common().add(new UniqueFieldValueConstraint(Persona.class, "dni"));


        ObjectContainer bbdd = Db4oEmbedded.openFile(config, "databaserrr.db4o");

        Persona p = new Persona("Pepe2", 25, "50667847L");

        try{
        bbdd.store(p);
        bbdd.commit();
        System.out.println("Se ha guardado correctamente");
        Query q = bbdd.query();
        q.constrain(Persona.class);
        ObjectSet<Persona> res = q.execute();
        }catch (UniqueFieldValueConstraintViolationException e) {
        System.out.println("The person with this DNI es already exists");
        }finally{
            bbdd.close();
        }
    }
}

---

我找到了捕获异常的解决方案：

catch (UniqueFieldValueConstraintViolationException e) {
        System.out.println("The person with this DNI es already exists");
bbdd.rollback();
}

catch (UniqueFieldValueConstraintViolationException e) {
        System.out.println("The person with this DNI es already exists");
bbdd.rollback();
}