Application Development Framework (ADF)

 

What is Oracle ADF

In computing, Oracle Application Development Framework, usually called Oracle ADF, provides a commercial Java framework for building enterprise applications. It provides visual and declarative approaches to Java EE development. It supports rapid application development based on ready-to-use design patterns, metadata-driven and visual tools.

ADF provides unified access to back-end technologies like databases, web services, XML, CSV, BPEL, and many more. Furthermore, ADF provides data binding to connect UI with back-end data controls.

 

Object Scopes in ADF

Scope indicates life time of an object. In addition to the normal object scopes that JSF defines, ADF added some more on top of it.

Types of Scopes

There are seven types of scopes in a Fusion web application. Scopes listed below in descending order with  first one having longest life time and last one lowest life time.

                                                          Application scope 
                                                                        |
                                                             Session scope 
                                                                        |
                                                           Page flow scope 
                                                                        |
                                                              View scope
                                                                        |
                                                            Request scope
                                                                        |
                                                        Backing  bean scope
                                                                        |
                                                                    None

• Application scope: An application scope object is available for the duration of the application and is shared among users. This scope may be used to hold static objects that are the same for all users.
• Session scope: The object is available for the duration of the session, which is user instance-specific. A use case for a session scope bean is a user info bean that stores information about a user, which is read from the database or an LDAP server, to avoid unnecessary queries.
• Page flow scope (Task flow scope): A pageFlow scope exists for each task flow instance and has a lifespan between request and session scope. The lifetime of the scope spans across all pages in a bounded task flow.
• Request scope: The object is available from the time an HTTP request is made until a response is sent back to the client. From another perspective, a request scope starts with a request to be issued from one view to another for navigation cases that don't perform a redirect but a default server-side forward. The scope spans across all non-view activities that follow the view of interest to the next view activity.
• Backing bean scope: The backing bean scope is comparable to the request scope, with the difference in that it exists for a specific client component. In general, all managed beans used in reusable components should be configured to backingBean scope. For example, bounded task flows that are designed to be regions on a page should use the backingBean scope if more than one instance of the task flow is expected to be on a single page.
• View scope (Page Scope): The object is available until the view ID for the current view activity changes. This becomes handy when you use partial page rendering. If you have a dependent list box, you might send a server request to refresh the list box. When a response is returned, the request scope will be gone but the view scope will be still there. Therefore, view scope can be used to store data when partial rendering request comes back. The view scope exists not only for views that are rendered by JSPX pages, but also for views rendered by page fragments, as is the case in task flows that are built to execute in a region. The view scope of the parent page is not accessible from components added to a page fragement in a region, and the view scope of a view in a region is not accessible for the parent page.
• None:  When you create objects (such as a managed bean) that require you to define a scope, you can set the scope to none, meaning that it will not live within any particular scope, but will instead be instantiated each time it is referenced. You should set a bean's scope to none when it is referenced by another bean.

Note:
Out of these View scope, Backing bean scope and page flow scope are ADF specific. Rest comes with JSF. This is the reason you must define ADF specific scoped backing beans ether in "adf-config.xml" or task flow.

What is DataBindings.cpx file in ADF

In ADF web application as soon as you drop a databound component on your page a DataBindigs.cpx file gets created. You may wonder what it contains? So, here it is:

The DataBindings.cpx keeps track of the individual page definitions files used within the project, as well as the DataControls mapping to such things as ADF Business Components Application Modules.

Till Jdeveloper 10.1.3 release there was no way to have multiple DataBindings.cpx files which was very much desirable as the project the size grows and being worked by multiple teams. Jdeveloper 11g added this capability to have multiple DataBindings.cpx files.

There is a new file in 11g called adfm.xml which is used to keep track of all such DataBindings.cpx files in the system. So, when breaking your DataBindings.cpx you need to take care to create an entry in the adfm.xml. You also need to make sure to have unique application id attribute value for each entry.