Implementation

The BC4J-VSM entities are implemented in the oracle.otnsamples.vsm.entities package, and the views are implemented in the oracle.otnsamples.vsm.views package.

The Oracle9i JDeveloper environment comes with comprehensive tools support for putting the BC4J framework components to use in J2EE applications. You use interactive wizards, editors, property inspectors, and UML diagrammers to create, enhance, and deploy your BC4J components. These tools are tightly integrated within a complete Java IDE that includes debugging, deployment, and source control support, so you can work from the beginning to the end of your J2EE application development lifecycle with one tool.

When you use a BC4J wizard to create entity objects from existing tables (reverse generation), it creates one entity object for each database table. It creates an entity attribute for each column in the database table; each attribute can have the same name as the column or a different name that is more meaningful to your business application. The attribute definitions of an entity object reflect and enforce the properties of the respective database columns, including data types, column constraints, and precision and scale specifications. An entity object can have an attribute for each column or you can use a subset, for example, if you don't need to work with that column or if a table contains information for more than one entity.

You can also use BC4J wizards to define entity objects, and their attributes, without starting from an existing database table (forward generation). When you use a wizard to generate database tables from entity objects, it creates a table for each entity object, a table column for each entity attribute, and column constraints based on the entity attribute settings. In addition, you can use the Entity Constraint Wizard to define table constraints.

The best place to write your business logic is in entity objects, because they consistently enforce business logic for all views of data, accessed through any type of client interface. Business logic includes the following items:

• business rules and policy - When adding or modifying data, you can ensure that the data complies with your organizations' procedures before adding it to the database. For example, you could increase the salary when an employee is promoted, give an employee three weeks of vacation after they have been at a company three years, or change the status of an order to shipped after all items in an order have been mailed to a customer.

• validation logic - When adding new data, you can ensure that the data is valid before storing it in the database. For example, you could ensure that a job code is a valid job code.

• deletion logic - You can make sure that data is deleted only when appropriate and that any dependencies are handled. For example, you could prevent an on-leave employee from being removed.

• calculations - You can efficiently perform data calculations in the business logic tier. For example, you could calculate an employee's monthly pay based on an hourly rate.

• default value logic - When creating new data, you can add appropriate default values. For example, you could provide a default benefit plan based on an employee's job code.

• security - You can make sure that data is read and modified only by users with that authority. For example, you could ensure that only the direct manager can change an employee's salary. Business logic in an entity object provides immediate feedback to the user if changes are inappropriate. This way, the in-memory business model always remains consistent.

You can create default view objects in the following wizards: Business Components Project Wizard or Editor Package Wizard or Editor Entity Object Wizard You can create default view links, based on existing associations, and a default application module by using the Business Components Project Wizard or Editor or Package Wizard or Editor.