7.1 Introduction to Entity-Based View Objects

An entity-based view object supports updatable rows. The view object queries just the data needed for the client-facing task at hand, then cooperates with one or more entity objects in your business domain layer to automatically validate and save changes made to its view rows. Like the read-only view object, an entity-based view object encapsulates a SQL query, can be linked into master/detail hierarchies, and can be used in the data model of your application modules.

By the end of this chapter, you will understand the concepts shown in Figure 7-1:

• You define an updatable view object by referencing attributes from one or more entity objects.

• You can use multiple, associated entity objects to simplify working with reference information.

• You can define view links based on underlying entity associations.

• You use your entity-based view objects in the context of an application module that provides the transaction.

• At runtime, the view row delegates the storage and validation of its attributes to underlying entity objects.

This chapter explains how instances of entity-based view objects in an application module's data model enable clients to search for, update, insert, and delete business domain layer information in a way that combines the full data shaping power of SQL with the clean, object-oriented encapsulation of reusable, domain business objects. And all without requiring a line of code.

Figure 7-1 View Objects and Entity Objects Collaborate to Enable an Updatable Data Model

Note: The examples in this chapter use the same basic SRDemo application business domain layer of ServiceRequest, ServiceHistory Product, User, and ExpertiseArea entity objects from Chapter 6, "Creating a Business Domain Layer Using Entity Objects". To experiment with a working version of the examples, download the DevGuideExamples workspace from the Example Downloads page at http://otn.oracle.com/documentation/jdev/b25947_01 and see the EntityBasedViewObjects project.