Design strategy of database class

Question

Hello,
I am developing a (XML-)DOM-based database class, storing specific information in trees and providing some public methods modify all database content (add, remove, etc.) All these methods work with path parameter of the type String, to access objects in the DB.
Now I've decided to reimplement the class and do it this way: Add a public method
DatabaseObject getObject(String path)
to the class. This method returns a new-created DatabaseObject. The interface DatabaseObject, provides methods like getName(), getProperty(), ... getChildren(), ... So you can deal with the objects itself and you do not have to ask the database class.
I have planned to create a class DatabaseObjectImpl which implements the DatabaseObject interface. Database.getObject created then a new instance of a DatabaseObjectImpl object.
My question is: What ways are possible to implement the DatabaseObjectImpl transaction with the parent database class. First a thought of implementing it this way. DatabaseObjectImpl is given the Database by its construction (in the constructor). Every time a DatabaseObject does data in-/output, it uses the methods in the parent database. (A database object also "knows" its path in the DB, also given by its construction). But I don't like this design.
Is there a way of letting the DatabaseObjectImpl's do the modification securely by itself? The database uses Xerces-J DOM-Documents. There is one catch, I don't know, how to secure it:
A user of Database fetches a DatabaseObject A to the path "/Java/is/great" via the getObject method in Database. Later, he also fetches a DatabaseObject B of "/Java". Now he calls B.delete(). Right now the object A should be valid, but the subtree /Java does not exist anymore.
What is the professional way, to solve this problem?
Was my first thought (let the database do all modification, called from objects) better than implementing the modification in the database objects?
Is my idea of providing objects to modify the database content bad?
Frank Wefers

Answer 1

I'm using XML via DOM as storage of the data of the database class. But I don't want to let the user of my class work on the DOM document. I want to provide him a database specific interface for modifying the db. The question, who can this be done care securely, if I want to give the user of my class instances of special objects, "DatabaseObject", which handle the modification and so on.
I did not like the way to do all modification directly through the instance of the database class.
An example:
Getting the name of an object in the database at the path
/root/folder/object:
Method A: Via Database-class methods (which I don't want)
String name = db.getObjectName("/root/folder/object");
Method B: Via Objects which handle everything:
DatabaseObject object = db.getObject("/root/folder/object");
String name = object.getName();
Via the second way, it would be also easy to do something like this:
object.getChildren();
object.getParent();
object.appendChild(new DatabaseObject("New Name"));
and so on...
So this DatabaseObject-class must in some way deal with the database class, which covers the database information. The DatabaseObject is only for simplify the handling.
How should the Database and the DatabaseObject be implemented securely (see figured problem in my first posting) regarding their communication?
Greetings,
Frank