There are multiple tables in my database. Each table has a primary key, and the table that relates to other tables has foreign keys. I have to match the primary key and foreign key to go from one table to another. The specifics are spelled out below:
The first table has login, pwd, and a primary key as fields, the second table contains completely different fields plus a primary key and foreign keys. The fields in the third table are different from those in the first and second tables plus its primary key. Queries to the third table can be made only if the user login and pwd are found in the first table, and through the second table's relation to the first table and the third table�s relation to the second table.
The fields of all those tables may be accessed concurrently, but the fields are "read-only" (for the time being).
I have a
servlet to handle browser interactions. And I have a session bean to handle the workflow and business logic. However, I am confused with the choices between VO and entity beans.
I first thought that I should use value objects to represent the data fields of the specific rows I looked for in those tables. Here is what I read about Value Object:
If a business object merely represents a structure to hold data fields, and the only behavior it provides are get and set method for the fields, then it would be wasteful of system resources to implement it as an enterprise bean. To avoid expensive remote methods calls (system resources and network bandwidth) to get the value of entity object fields, a value object is used to represent the details of the entity object. Only one remote call is required to retrieve the value object and then a client�s request to query the state of the object can then be met via local get methods on this details object.
On my second thought, I think I should use entity beans to represent the specific rows I am looking for in those tables because I must use primary key and foreign key relations to go from one table to another.
I do not use DAO because I am using CMP. The first call is within the session bean. It is a remote call to look for a specific row in the first table in my database. Subsequently, the mapping of the row in the first table to the second table, and the mapping of the row in the second table to the third table are all invoked on the �local interfaces� of those entity beans.
client(browser)-->front controller(servlet)-->session facade(session
ejb)-->entity ejb-->entity ejb -- > entity ejb
Please advise if this is the right design. Am I on the right track? Is there improvement to be made?
