Oracle JHeadstart Developer's Guide - Downloads - Oracle

3.3. Creating View Objects and Application Modules
This section discusses the development tasks related to creating the data model layer,
consisting of View Objects, View Links and Application Modules. The following topics
are discussed:
• Creating View Objects and View Links
• Renaming View Objects and View Links
• Inspecting and Setting Key Attributes of a View Object
• Setting View Object Control Hints
• Determining the Order of Displayed Rows
• Creating Calculated or Transient Attributes
• Setting up Master-Detail Synchronization
• Defining View Links and View Object Usages for Lookups
• Testing the Model
3.3.1. Creating View Objects and View Links
When creating a View Object you need to determine whether the data queried through
the ViewObject should be updateable in the user interface (web pages). If so, you need to
create an updateable ViewObject, which is based on a primary Entity Object. If the data
is read-only in the user interface, it is more efficient to create a read-only View Object,
which is a View Object not based on an entity object with a custom SQL query that you
need to enter manually.
A typical example of read-only View Objects, are View Objects used to populate lookup
data in the user interface, typically exposed through a drop down list, or List of Values
window.
3.3.2. Renaming View Objects and View Links
If you have used the “New Default Data Model Components” wizard, we recommend
that you rename the View Objects and View Links to comply with the naming standards
you have set up for your project (see chapter 2). If you create the View Objects and View
Links one-by-one, you can assign proper names right away.
3.3.3. Inspecting and Setting Key Attributes of a View Object
Under the covers, an ADF Faces table uses the View Object findByKey() method for its
row management. This row management is used by the ADF Faces table to update the
correct underlying row, when a user has changed one or more values in the ADF Faces
table. Built-in ADF Data Binding layer actions like setCurrentRowWithKey and
setCurrentRowWithKeyValue also rely on the findByKey() method. For this method to
behave reliably, two conditions must be met:
• Each View Object must have at least one key attribute
• The key attribute(s) should be non-updateable
JHeadstart Developer's Guide Creating ADF Business Components 3 - 15