HOWTO: Expose Entity Object Methods to Clients

Question

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>
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Answer 1

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
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