Business Object, Overview - Advanced Java Fat-Client-Development

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Last revision of this document:
2006-07-14

This document gives an overview of the different classes belonging to a Business-Object.

Using Business Objects to handle data-storage and retrieval is a general introduction of the general architecture for persistent data (in simpler words: writing to / reading from database-tables).
It gives an overview how the different classes cooperate.

Base Class,
containing variables for the common attributes and for reporting the status to calling methods.
Business Object for a dedicated business-case,
containing variables for the business-case and methods for checking and calculating.
Business Object with methods for the client-side.
Contains methods to get / set the values from / to GUI-Elements,
Decides what version of the application is running (Stand-Alone or Client to a Java-Application-Server) and controls the Business Objects for the server-side depending on the version.
The control of the server-side Business Objects is done either within the application (if the version is Stand-Alone) or over the EJB-mechanism (if the version is Client to a Java-Application-Server).
Business Object with methods for the server-side.
Controls the access to database-tables by using the methods of Data-Base-Access Objects (one class for each database-table).

This class contains
* the Common Attributes for all database-tables (see the linked document for an explanation),
* variables to pass a Status-Code and a Status-Message (in the case that the Status-Code signals an error),
* constants for Status-Codes that are common to all Business Objjects and
* a method to copy the Common Attributes from one business-object to another.
To see the code for this class, please follow this link.

This class is tailored to a business entity (e.g. a 'product', a 'Delivery Notice' or an 'Invoice') and contains
* variables specific for the business entity,
* constants for Status-Codes that are specific for this business entity,
* a method to copy the variables from one business-object (of this class) to another and
* methods requiered specific for this business entity
(e.g. calculate the weight of a delivery out of the 'Product's individual weight;
where the products are referenced in the position of the delivery notice.
To see an example code for a general class, please follow this link.
For a detailed description and a guideline to code a General Class, please follow this link

This class expands the General Class in the following fields:
* Methods to transfer the values of the variables (defined in the General Class) to / from GUI-Elments (Text-Fields, Combo-Boxes, etc).,
* Methods to be called when data should be stored or retrieved from the database.
   These methods construct and control the fitting Server-Side Class
   depending if the Run-Version of the application is 'Stand-Alone' or 'Client-Server'.
   Please se the detailed description for more information !
To see an example code for a client-side class, please follow this link.
For a detailed description and a guideline to code a Client-Side Class, please follow this link

This class expands the General Class in the following fields:
* Methods to read from one or more database-tables by calling the classes for Data-Base-Access.
   There can be various read-methods inplemented to use different attributes as search criteria.
* When storing data, a mechanism is used to incorporate the history of changes.
   See Common Attributes for all database-tables for a detailed description how change-history is implemented.
* When storing data, a verification process is run to prevent 2 objects
   with the same 'User-known primary key' and overlapping validity.
* When storing data, a verification process is run to check
   that the object was not changed since the read from the database.
To see an example code for a server-side class, please follow this link.
For a detailed description and a guideline to code a Server-Side Class, please follow this link.

A simplified overview how data is written to / read from a database: Using Business Objects to handle data-storage and retrieval.