05QueryingPersistingData.ppt

Copyright © 2008, Oracle. All rights reserved.
Querying and Persisting Data

5 - 2
Objectives
After completing this lesson, you should be able to do the
following:
• Describe the characteristics of an ADF BC view object
• Create ADF BC view objects that can be used for data
queries in a Web application
• Modify SQL statements in view objects
• Explain how entity objects relate to database tables
• Describe the persistence mechanism of entity objects
• Create entity objects from database tables
• Create associations between entity objects
• Create updatable view objects based on entity objects
• Link view objects to one another
• Refactor business components

5 - 3
Using View Objects
CustomerStatus
CustomerStatusRO
Updatable
View Object
ID
Name
Status

5 - 4
Characteristics of a View Object (VO)
View objects:
• Represent a query
• Are used for joining, filtering, projecting, and sorting
business data
• Enable you to have a view of data that is specific to one
part of your application
• Can be constructed from a SQL statement, static values,
or populated programmatically
• Can also be based on any number of entity objects
View
objects
PriorityOrderVO ItemListVO
Reusable
Query Components

5 - 5
Creating View Objects for Queries
1
2
Invoke the Create View Object
Wizard. Initialize project for
Business Components.

5 - 6
3 Specify package, name, and kind of data.

5 - 7
4
Enter the SQL query,
or use Query Builder.

5 - 8
5
Create bind variables
and set attribute
properties as needed.

5 - 9
6 Optionally, create Java
classes (if adding
programmatic business
logic).
7
Optionally, create a new
application module or
add to an existing one.

5 - 10
Testing View Objects with the Business
Components Browser
1 Run the application module.
3
Double-click the
view object
instance.
2
Provide
connection
details.

5 - 11
Characteristics of an Entity Object (EO)
Entity objects:
• Represent a row in a database table or other data source
• Handle database caching
• Contain attributes representing the database columns
• Encapsulate attribute-level and entity-level validation logic
• Can contain custom business methods
CustomerEO OrderEO

5 - 12
Using Entity Objects to Persist Data
CustomerEO
Id
Name
Status
Email
Entity
object
Attributes
Database
table
Status List
(Gold Silver Platinum)
Validation
rule
ID
201
NAME
Steve
STATUS
Gold
Email
msmith@company.com
202 Mike Silver dgonzales@company.com
CUSTOMERS

5 - 13
Creating Entity Objects
The Create Entity Object Wizard:
Name page
Attributes page
Attribute Settings page

5 - 15
Creating Entity Objects
from Tables, Views, or Synonyms
When you create an entity object, JDeveloper:
• Interrogates the data dictionary for information
• Infers primary key, or creates one from RowID
• Creates implicit validators for database constraints
• Creates the XML component definition file
(<EO_name>.xml)
• Creates optional Java files if selected, such as entity object
class <EO_name>Impl.java
• Generates associations based on foreign keys, if
applicable (<Association_name>FkAS.xml)

5 - 16
Synchronizing an Entity Object
with Changes to Its Database Table
ALTER TABLE USERS
ADD (security_question VARCHAR2(60));

5 - 17
Generating Database Tables from Entity Objects
Right-click package and
select Create Database
Objects.
In Create Database Objects
dialog box, select objects to
create.
Use with caution!

5 - 18
Characteristics of Associations
• Define a relationship between EOs
• Facilitate access to data
in related entity objects
• May be based on database
constraints
• May be independent of database
constraints
• Are used in defining
validations and LOV metadata
• Consist of a source (master)
and a destination (detail) entity
Source Destination
OrdersPersonsFkAS
Association
PersonEO OrderEO

5 - 19
Creating Associations
Use the Create Association Wizard:
Name page
Entity Object page
Association Properties page
Association Query page

5 - 20
Association Types
• Association
– Entities are related but not
completely dependent.
– Either end of the association can
exist without the other.
– Either can be deleted without
deleting the other.
• Composition
– Destination entity is completely
dependent on source entity.
– Source entity owns destination
entity.
– No destination entity can be
created without the owning entity
existing first.
– Source entity cannot be deleted
without deleting all its associated
destination entities.
Customer Order
Order Order Item

5 - 21
Characteristics of
Updatable View Objects
Entity Object View Object
select name, status
from customers
order by name
CustomerStatusVO
CustomerEO
ID
Name
Status
Email
Mike Silver
Steve Gold
Name Status
Database
Table
ID
201
NAME
Steve
STATUS
Gold
EMAIL
Steve@abc.com
202 Mike Silver Mike@abc.com

5 - 22
Creating Updatable View Objects
Name page
Use the Create View Object Wizard:
Entity Objects page

5 - 23
Creating Updatable View Objects:
Attributes and Settings
Attribute Settings page
Attributes page

5 - 25
Query

5 - 27
Additional Settings

5 - 28
Interaction Between Views and
Entities: Retrieving Data
• The view object queries the database directly.
• Data retrieved by the query is saved to the entity object’s
cache.
• Nonpersistent attributes are stored and retrieved from the
view object’s cache.
Select
VO
EO
Select
(12*monthly_sal)
VO

5 - 29
Interaction Between Views and
Entities: Updating Data
• The view object updates the entity object’s cache.
• The entity object commits to the database.
Update
EO VO
Commit

5 - 30
Creating a Join View Object
Join is based on
association
between
entities.

5 - 31
Including Reference Entities
in Join View Objects
1 2
3

5 - 32
Cascading Master–
Detail to Any Depth
Master to Single
Detail
Master to Multiple
Details
Creating Master–Detail Relationships
with View Objects
Different types of master–detail relationships are
supported.

5 - 33
Linking View Objects
Joined queries and view links
display information differently.
Use the Create View Link
Wizard to create a view link
between CustomerVO and
OrderVO view objects.

5 - 34
Comparing Join View Queries with View Links
Join view queries:
• Contain all attributes from main and referenced entities in
a single row
• WHERE clause relates key from main table with foreign key
in referenced tables
View link queries:
• Use a bind variable to relate detail records to key for
selected master record
• Append WHERE clause with bind variable to the base SQL
query for the source or destination view object

5 - 35
Refactoring Objects
With refactoring you can:
• Rename objects, such as
associations and view links
• Move objects or packages
to a different package
• Change all references
throughout the application

5 - 36
Summary
In this lesson, you should have learned how to:
• Describe the characteristics of an ADF BC view object
• Create ADF BC view objects that can be used for data
queries in a Web application
• Modify SQL statements in view objects
• Explain how entity objects relate to database tables
• Describe the persistence mechanism of entity objects
• Create entity objects from database tables
• Create associations between entity objects
• Create updatable view objects based on entity objects
• Link view objects to one another
• Refactor to move and rename associations and links

5 - 37
Practice 5 Overview:
Creating Entity Objects and View Objects
This practice covers the following topics:
• Creating read-only view objects to support LOVs
• Creating entity objects for tables that need to be updated
in the application
• Creating associations
• Creating updatable view objects
• Creating view links
• Refactoring associations and links

05QueryingPersistingData.ppt

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