Apps To Fusion

Ram Kumar emailed me a very simple question, "What is the difference between D2K form and OA Framework". Its a very innocent but important question for someone that desires to make transition from D2K to OA Framework. I hope you have already read and implemented OA Framework Getting Started .

To answer to Ram's question, I will re-visit my own experience of implementing HelloWorld program in "OA Framework". When I implemented HelloWorld an year ago, I had no clue as to what I was doing & why I was doing those steps. I merely copied the steps from Oracle Tutorials without understanding them. Hence in this article, I will try to explain in simple manner the meaning of OA Framework HelloWorld Program and compare the steps to D2k forms[where possible]. To keep things simple, only basics will bediscussed.

Following key Steps were needed for HelloWorld[visit Oracle's tutorial for complete list]
Step 1. Created a new Workspace and a new Project as dictated by Oracle's tutorial.
When defining project, you will specify a default package, which in this case was oracle.apps.ak.hello
This means the following:-
a. ak is the short name of the Application in Oracle [it means fnd_applications.short_name].
b. hello is the name of your project.

Step 2.
Next, you will create a OAPage within hello project.
Think of OAPage as the fmx file itself in D2K. I am saying so because this page gets attached to the form function.
a. This page will be created within hello project, hence the package name oracle.apps.ak.hello.webui
b. Note the webui, its a convention to have page in webui,means this page represents the Web User Interface
c. You will assign the default AM [OAApplicationModule]. Think of AM "Connection Manager" and "Transaction State Manager" for your page.
I can't co-relate this to anything in D2k, as there is no concept of Connection Pooling and that D2k is not stateless. Reason being that as soon as you kick off a D2K Form, it connects to a single session of Oracle and sticks to that single Oracle database session. So is not the case in OAF, hence AM is needed.

Step 3.
You create Region within the Page.
a. Region is what will store your fields. Text input fields will be of type messageTextInput. Think of Canvas in D2K[to an extent].
b. You can have nested regions. Stacked Canvas in D2K comes the closest to this component of OA Framework.

Step 4.
Add a button to one of the nested regions.
a. The itemStyle should be submitButton, in case you want the page to be submitted when this button is clicked.
b. There is no WHEN-BUTTON-PRESSED trigger in OAF. In Framework, you will add a controller java code to handle events like Form Submit button clicks. jDeveloper generates the default code for you. Primarily two functions[should I call methods] will be createdprocessRequest[for UI Rendering Handling] and processFormRequest.
Think of processRequest as WHEN-NEW-FORM-INSTANCE, though processRequest is very restrictive.

Step 5.
In the controller to access the value in field "HelloName" the command is
String userContent = pageContext.getParameter("HelloName");
In D2k, we used :block.field. In OAFramework, at submission of page, all the field values get passed into to OAPageContext object.
a. Use getParameter to access the field value
b. To set the value of the field, use
OAMessageTextInputBean fieldHelloName =
(OAMessageTextInputBean)webBean.findChildRecursive("HelloName");
fieldHelloName.setText(pageContext,"Setting the default value" );
Note when setting field value in controller:
Note 1. Do not set the value in processFormRequest
Note 2. If the field comes from ViewObject[in latter tutorials], then do not use setText in controller.
Note 3. For control fields[that are not based on ViewObjects], you can use setText to assign values in processRequest method.


Lets take some notes to expand beyond the HelloWorld Project
1. In D2K-forms we sort of created a Window, attached to Canvas, and then fields within that Canvas.
However in OA Framework, think of Page being fmx/Window, think of Region being a Canvas, and fields being within Regions.
This is not a formal/accurate understanding of analogy between D2k and Framework, but is close to being logical.
2. In D2k, your Forms fmb file was compiled to fmx. It was fmx file that was deployed on mid-tier.
In case of OAF, your OA Page is nothing but a XML file. We call this MDS [meta data].
Whatever name you give to "Page" in OAF, an XML file of the same name gets created. This xml file must then be loaded into database by using XMLImporter command.
See article on XML Importer if interested.
3. Apart from MDS XML file, almost everything else is merely deployed to your mid-tier. Usually this is underneath $JAVA_TOP/oracle/apps/../..
All your java files will go underneath java top/oracle/apps/../.. etc.
4. When building your tutorial, ignore the steps for setting "Attribute Sets". These are not mandatory. Oracle might just have developed their tutorials without including these. Think of these like Visual Attributes of D2K forms [to an extent]
5. Controller is where you will write any java code in OA Framework. You can create a Controller per Page or have a different Controller for each of the Regions with the same Page.
6. In the method processFormRequest of the Controller, you can access the values of the page by using notation pageContext.getParameter("<fieldname here>"). This method processFormRequest is executed when the OAF Screen/Page is submitted by click of a button.
7. Inside the controller, all the Database Related interactions for example interaction with View Objects happens via Application Module.
But why so? Because Application Module Manages the transaction state of the Application.
OAApplicationModuleImpl oaapplicationmoduleimpl = (OAApplicationModuleImpl)oapagecontext.getApplicationModule(oawebbean);
OADBTransaction oadbtransaction = (OADBTransaction)oaapplicationmoduleimpl.getDBTransaction();
8. In D2K, we have control block or a block based on database view. Similarly, in OA Framework, if the field does not have viewObject attached, then its like a control field. Hence in HelloWorld example, field HelloName is a control field[in D2K terminology]. A viewObject can either be based on a view/table.synonym or on a SQL statement.
9. I wish to access the fields in multi record block that is based on viewObject. Can I do this in Controller?
Sure you can. To traverse through those records, do the below
a. Get the reference to the ViewObject using (OAViewObject)oapagecontext.getApplicationModule(oawebbean).findViewObject("VO Name Here")
b. Loop through the records in View Objects using count returned from oaviewobject.getFetchedRowCount()
c. For each record, fetch the value of the fields within the loop as
oracle.jbo.Row row = oaviewobject.getRowAtRangeIndex(loop index here);
(String)row.getAttribute("Column name of VO here ");



What is the difference between processRequest and processFormRequest?
These two methods are available in the Default Controller class that gets created.

processFormRequest
This method is commonly used to react/respond to the event that has taken place, for example click of a button.
Some examples are
if(oapagecontext.getParameter("Cancel") != null) {Do your processing for Cancellation/Rollback}
if(oapagecontext.getParameter("Submit") != null) {Do your validations and commit here}
if(oapagecontext.getParameter("Update") != null) {Do your validations and commit here}
In the above three examples, you could be calling oapagecontext.forwardImmediately to re-direct the page navigation to some other page if needed.


processRequest
In this method, usually page rendering related code is written. Effectively, each GUI component is a bean that gets initialised duringprocessRequest.
Those who are familiar with D2K forms, something like pre-query may be written in this method.

< Prev		Next >