Polymorphic Entity Object on Database View ?

Hi all,
We want to implement polymorphism on business components (EO, VO). I have some questions :
1) On the supertype-subtype, is it better to use ONE table for all subtypes , or using different tables with each subtype ?
2) Is it recommended to use Entity Object on a Database View + Instead Of Trigger ?
Thank you very much,
xtanto

Our recommendation is in the ADF Developer's Guide for Forms/4GL Developers, in section 26.6 "Using Inheritance in Your Business Domain Layer". A single table is the simplest and most functional.
There's nothing wrong with using a view with instead-of triggers, as long as your not wasting your time to write PL/SQL that would be duplicating what ADF BC could automatically do for you using join view objects, with multiple entity usages, against multiple underlying tables. In general, you don't need to use views with instead-of triggers. See section 26.5 "Basing an Entity Object on a Join View or Remote DBLink" if you do.

Similar Messages

Problem with using multiple Entity Objects in a view Object.

Hi
Thank you for reading my post
I have create 3 Business components for 3 of my database tables and now
I must add 3 tables in a View object so i used Jdeveloper Wizard to create the View Object.
-I Add Entity Objects which are business components to this view (In Step 2 of the Create Vview Object wizard).
-In step 3 that I add Attributes all my attributes are marked as Transient
Can some one explain why it happens?
I need one of those tables to be updateable and two other tables are not updateable.
What should should i do to achieve this?
I should say that tables does not have any database relation (Foreign Key I Mean).
Thanks.

Hi user505214
When you created your VO, on selecting the second EO, you'll note at the bottom of the same page on the wizard/editor, checkboxes for updatable or by reference. By default reference is checked and this will make your second EO's attributes transient.
In the JDeveloper Developer's Guide for 4GL/Forms programmers, the following sections outline the difference between updatable or by reference:
7.5 Including Reference Entities in Join View Objects
27.9 Creating a View Object with Multiple Updatable Entities
Make sure to read 27.9 if updatable is what you want as it indicates you may need to add some additional code.
Hope this helps.
CM.

Extended but NOT polymorphic Entity Object ?

Hi,
We are trying to implement the OO features of ADF BC, i.e : Inheritance and Polymorphism, to reuse the logic in EO. I need some confirmation below to make sure we apply it correctly :
1) We can Extend Entity Object WITHOUT assigning any discriminator, can't we ?
(this is what I call Extended but NOT polymorphic )
If the answer is yes , then I have further question :
2) In our Order Processing module of our ERP application, there are following entity object : SalesOrder, Invoice, SalesReturn, CreditNote
And there are four underlying database tables : SalesOrder, Invoice, SalesReturn, CreditNote.
They are surely DIFFERENT transaction BUT they have COMMON attributes (and validation), This is why I call it "Extended but NOT polymorphic".
The common attributes are :
- DocID (PK)
- DocNumber
- DocDate
- Warehouse
- Customer
- Salesman
- TermOfPayment
- DueDate
So I create one BaseOrderEntity as super class entity. Then I create four entity objects that extend the base entity :
Entity : SalesOrder, Extend : BaseOrderEntity, Database Object : SalesOrder
Entity : Invoice, Extend : BaseOrderEntity, Database Object : Invoice
Entity : SalesReturn, Extend : BaseOrderEntity, Database Object : SalesReturn
Entity : CreditNote, Extend : BaseOrderEntity, Database Object : CreditNote
Is this the correct way to apply it ?
In other word, is this the correct use case ?
Thank you very much,
xtanto.

Starting in JDeveloper 10.1.2, the ADF runtime throws an error if it detects that you have a superclass and subclass entity objects without properly-configured discriminator attributes. If you do not intend to instantiate the superclass, just assign it a descriminator attribute with a value that will never occur in real-life, like NULL or 'x' or whatever.
It will be simplest if all your family of subclasses were stored in the same table, although that is not required. It simply makes the polymorphic queries easier.
If you want to avoid the runtime check for the discriminator's being properly configured, because you know that your application will never run the chance of loading the same row into the entity cache as two different entity definition types, then you can get a property jbo.abstract.base.check in your configuration (or as a System property) to the value false and then the check is not performed.

CMP Entity Bean from dataBase views

Hi forum,
I Have to migrate an existing application to JEE (with EJB3).
In this application there are a lot of dataBase views.
I'm new in EJB3 and I don't know how to structure cleanly entity beans (Specially when it are created from dataBase views).
My problem is that for each query made from the same dataBase view I almost have to create a new entity bean with a different @Id.
What can I do to to avoid it?
I had thought to genrate a new @Id (attribute not persistent) but I think is not possible. It's right ?
Someone can help me ?
Thanks

"CMP provides you with database independence and less coding efforts."
BMP is not database dependent, unless you invoke database specific things in your SQL (something I do not do). CMP on the otherhand is inherently appserver specific (which was it's goal when BEA, IBM, et al. came up with it), and still limits your design possibilities. See this thread for an example:
http://forum.java.sun.com/thread.jsp?forum=13&thread=318785
As for less coding effort, that is a relative statment. Yes a simple CMP bean requires less coding to develop the first time. I personally view a few lines of SQL to load and store the data as being fairly trivial. But that needs to be offset with the problems inherent in using appserver specific CMP implementations.
As an example, try mapping WebSphere CMP to a pre-existing database without using IBM's IDE. It's an incredible pain in the ass since WebSphere does not come with a "meet-in-the-middle" solution. Any J2EE developer that has had the experience of working with different appservers (especially if they have had to port an app, as I have) can attest to the complications that arise with each implementation.
A BMP bean, written with non-DB-specific SQL, is the most portable, most flexible approach to EntityBeans. Yes, it requires the developer to be able to write some SQL, which should not take a significant amout of time. WRT queries, you have to write them, either SQL, EQL, or some appserver specific format.
As an aside, the use of code generators to simplify the creation of EJBs lends itself well to BMP. By using a (or writing your own) code generator, you can mitigate the annoying SQL bugs that creep up early in development.

Entity Bean on dataBase views

Hi forum,
I Have to migrate an existing application to JEE (with EJB3).
In this application there are a lot of dataBase views.
I'm new in EJB3 and I don't know how to structure cleanly entity beans (Specially when it are created from dataBase views).
My problem is that for each query made from the same dataBase view I almost have to create a new entity bean with a different @Id.
What can I do to to avoid it?
I had thought to genrate a new @Id (attribute not persistent) but I think is not possible. It's right ?
Someone can help me ?
Thanks

Hello Kenny,
The view can be treated the same as a table, it just needs to have some field or set of fields that can uniquely identify rows for it to be able to map to an Entity. Unless the view has rows that are exact duplicates, in the worst case you can use the entire row as the primary key.
Best Regards,
Chris

Problem with database schema objects in the entity object wizard

Hi All,
When creating a new entity object, I am facing a problem with database schema objects in the entity object wizard, database schema objects (check boxes for tables,synonyms...) are disabled. Actually I am using a synonym but I am not able to select the synonym check box.
Can any of you folks tell me how to enable the database schema objects (check boxes for tables,synonyms...).
Thanks in Advance.
Raja.M

Make sure your using rite version of jdeveloper..
Make sure your using apps schema and check whether your able perform DML operations in the schema vis sql developer.
--Prasanna

Calling database stored function from Entity Object

Hi,
I want to call a database stored function from create() method of Entity Object.
Database function returns some value.
Can anybody suggest me some way to do it.

You can try the following:
make a String whit your function call, I dont know if this is the correct SQL syntax for a function, it should be for a stored procedure.
String call = "begin; callyourfunction; end;"
PreparedStatement ps = getDBTransaction().createPreparedStatement(call,0);
ps.execute();
ResultSet rs = ps.getResultSet();
You can now read the data from the function from the rowset.
Be sure to cleanup the PreparedStatement when your done whit it to avoid open database connections.
ps.close();ps=null;

Using database views in ADF mobile client application

Hi,
I am using Jdeveloper 11.1.1.4 and WLS 10.3.4.
I have developed a POC in ADF mobile client application both with and without synchronization. However, both work with entity objects based on tables.
I need to use database views instead of tables. When I try to include entity object (based on views) in the view object, it shows an error saying "Only the entity objects based on tables can be selected"
Please guide me if there is a work around for this.
Also, please let me know if there is way to develop an ADF mobile client application skipping the use of entity objects at all and using view objects directly to specify the database query and fetch data from the database.
Thanks in advance.
Ansh
Edited by: ansh on Mar 28, 2011 5:40 AM

Hi, Ansh:
Currently, out of box, ADF Mobile Client does not support synchronization against Database Views. This is because Mobile Server imposes some schema restrictions to ensure synchronization with multi-table views would work correctly. This schema restriction requires, for example, the view must have a primary parent table with key defined, and also all base table must be included in the data publication. These dependencies requires manual resolution and advanced planning, and is managed outside of the ADF Mobile Client/JDeveloper project.
To continue development, you would need to create server Entity Objects directly against the base tables. You can then create the mobile ADF Business Component (EOs, VOs, etc). You can then create View Objects in your ADF Mobile Client application based on the database views, in order to retrieve the data you need exactly. In other words, instead of basing EO on the database view, create View Objects in the mobile applicaiton to mimic what you had in the View Object.
Is there any other reason why you would need to access data via database views, instead of directly against base tables?
Thanks,
Joe Huang

Business Components and Database Views - Trouble Creating

I am trying to create a business component that contains a View that I created in my database. When I get to the fnnal step of creating the business component and it begins to generate the XML and Java code, it bombs out and says that the view object does not support ROWID. I just need to select only GridControl of this view.
Any suggestions/help would be appreciated. I could not find any info in the JDeveloper help.
null

Some options:
[list]
[*]Create the entity using the Entity Wizard instead of reverse engineering it from a table. In the entity wizard you can specify the table/view name, then indicate which attribute should function as the primary key.
[*]Don't bother creating an entity object for this view. You can just create a view object with an "expert mode" query that selects against your database view. It does not need an entity object. Note, however, that without an associated entity you won't get "uniquing" of entity level values, so if another view object being used by the same use changes the data that this grid is showing, the updates won't be automatically synchronized if you go this route.
[list]

Using Database Views in ADF

Hi,
There are Two Views in My Database and I need to join these Views as one new VO in my ADF app. (and then I need to join this VO with another entity in my app)
I tried to make Entity object of those Views but it seems that you can not make an Entity out of a Database View (and it reasonable !)
but how can I accomplish such scenarios ?
JDeveloper : 11.1.1.6
Thank you
Shahab

this is to poster.
am not hijacking this thread., i had a question with frank.
However, for CRUD operations this could soon become hairy.
go by creating two entities. Dependent on what needs to be updated in the database, you then override the doDML method of the EntityImpl classes with calls to >e.g. stored proceduresthis is to frank.
i need a confirmation for above statement.
if a dbview involves more than 1 dbtable means say as example: 3 table means
if i take a dbview as a single entity object means, how could i perform CRUD operation?it's not possible.. am right?.
so only you are saying take 2 eo make it a view (access through eo object),do crud operation seperate beyind business need.
so only you are saying become hairy

Database Views and Master-Detail using ADF

How would I create a master-detail form using a database view for the search-able master table and a database view as the detail table?
The detail-view will need to be update-able (adf-table) using an instead-of trigger to perform the updates to the database table.
Thanks in advance...

There are several sections in the ADF Developer's Guide about using views (http://www.oracle.com/technology/documentation/jdev/b25947_01/index.html):
- 26.4 Basing an Entity Object on a PL/SQL Package API
- 6.2.4 Creating an Entity Object for a Synonym or View
You can also try Steve Muench's web log: http://radio.weblogs.com/0118231/stories/2004/09/23/notYetDocumentedAdfSampleApplications.html
There are at least two (old) items there that involve view with instead-off triggers:
- Composite Entity Using Stored Procedure API to Create/Modify/Remove Master and Children
- Entity Object Based on View With Instead Of Triggers Avoiding Returning Into Clause
Jan Kettenis

Calling stored procedures from entity object and application module

Hello
I've put in place an EntiyImpl base class containg helper methods to call stored procedures.
I now need to call stored procedures from the application module.
Apart from creating an application module base class and duplicating the helper method code is there a way
to share the helper methods for calling stored procedures between the entity impl and application module impl ?
Regards
Paul

Does the helper code depend on features of a particular entity object instance, beyond its database transaction?
If so, I'm not sure I see how it could be used from an application module class.
If not, here's what you do:
Step 1:
Parametrize the database transaction--you might even want to. So instead of
protected myHelperMethod(Object someParam) {
DBTransaction trans = getDBTransaction();
change this to
protected myHelperMethod(DBTransaction trans, Object someParam) {
Step 2: make the method public and static--once you parameterize the DBTransaction, you should be able to do this.
public static myHelperMethod(DBTransaction trans, Object someParam) {
Step 3: Remove the method from your EntityImpl base class into a utility class:
public abstract class PlSqlUtils {
private PlSqlUtils() {}
public static myHelperMethod(DBTransaction trans, Object someParam) {
When you want to call the method from an application module, entity object, or even view object class, call
PlSqlUtils.myHelperMethod(getDBTransaction(), paramValue);
Unlike Transaction.executeCommand(), this lets you provide functionality like setting procedure parameter values, retrieving OUT parameter values, etc.
Hope this helps,
Avrom

HOWTO: Expose Entity Object Methods to Clients

By design, clients cannot directly access entity objects. The view object layer provides an extra layer of security--you can choose exactly what data and methods you want clients to see.
This HOWTO describes the process of exposing an entity object method to client programs.
First, if you don't already have one, you must base a view object on your entity object and add the view object to your data model. For full details of how to do this, see the help topics under
+Developing Business Components
--Working with View Objects, View Links, Application Modules, and Clients
+----Creating and Modifying View Objects, View Links, Application Modules, and Clients
For the purposes of this HOWTO, we'll assume that you already have an entity object, Employees, with a method on it, calculateBonus(),
and a view object EmployeesView based on Employees.
First, you must generate a view row class. A view row represents one row of the view object's cache; it corresponds to a view of a particular entity object.
To generate a view row class:
1. Right-click EmployeesView and choose Edit.
2. In the View Object Editor, select the Java page.
3. Select Generate Java File and Generate Accessors for the view row class.
4. Click Done. This creates a class called EmployeesViewRowImpl.
Next, you should add a "delegator" method to the view row class--a public method with the exact same signature as the entity method, that simply calls the entity method. For example:
public int calculateBonus(int rating) {
return getEmployees().calculateBonus(rating);
Next, you should export this method.
1. Right-click EmployeesView and choose Edit.
2. In the View Object Editor, select the Client Row Methods page.
3. Shuttle the method you just created into the Selected list and click Done.
This creates an interface called EmployeesViewRow that contains your method.
Now you can call the method from your client. You should cast the row returned by EmployeesView.current(), the <jbo:Row> tag, or a similar method or data tag to EmployeesViewRow.
For example,
<jbo:Row id="myRow" datasource="ds" action=Current>
<% out.println(((EmployeesViewRow) myRow).calculateBonus(3)); %>
</jbo:Row>
null

Hi Lisa,
There's a difference between exporting methods (on an application module, view object, and view row--this is done on the "Client Methods" tab of the view object and application module wizards and the "Client Row Methods" tab of the view object wizard) and making an application module remotable (which is done on the "remote" tab of the application module wizard).
You should always export methods you want clients to use--and you only need to do this on the application module if you've written methods on your application module (which I didn't in this HOWTO). You can still use these methods in local mode--the interfaces will be present locally. The advantage of exporting methods is that it doesn't lock you into local mode--you'll be able to change to remote mode later (if you decide that's the way to go) with minimal changes--because the interfaces will be present locally even when the implementation classes aren't.
By contrast, you should only make an application module remotable if you're planning on deploying in a non-local configuration. You can do this step right before deployment.
Hope this helps,
Avrom
null

ADF Entity Object: Securable Operation "Create"?

Hello,
I have the following scenario: Within one view I have a table bound to a view object that bases on an entity object. The view also contains a "create insert" button.
Now I want to secure the "create insert" operation with a certain application role. However, within the entity object I can only activate the removeCurrentRow, read and update options as securable operation. Is there any way to control the creation of new items?
Regards,
Michael

Hi.
welcome to forum!
Maybe this post can be useful http://andrejusb.blogspot.com/2011/03/how-to-enable-create-operation-security.html

Should ADF Entity Object Map to Database Table or View?

We are building a new 3-tier JClient/ADF application. We have mapped most entity objects directly to database tables. Now that we are preparing to deploy, our DBA is angry; he believes that all entity objects should be mapped to database views. The developers see this as a headache, UML can not forward/reverse changes, and now we have another layer of abstraction, which doesn't seem to serve a useful purpose. What is the best practice in a new 3-tier application?

Hi,
I'm still having problems but I found out why these tables are returning errors. The username I've been given by the DBA to connect to the database is CONSULTA, but this user is only for querying purposes, the actual objects reside on a differente schema, of course, which is PROD. So the line:
"CONSULTA"."ESTADOS"@"PROD@AYADEV_LOCATION" "ESTADOS"
raises an exception because the table ESTADOS is not located on that schema, but on PROD. If I query the table from SQL Plus with:
SELECT *
FROM [email protected]@AYADEV_LOCATION
then there's no problem at all.
Why is this? How do I instruct OWB to point to the correct schema or to avoind fully qualifying the table name?
Please help me, I'm kind of confused here.
Best Regards,
--oswaldo.
[osantos]

Polymorphic Entity Object on Database View ?

Similar Messages

Maybe you are looking for