25.4 Creating Generic Extension Interfaces

In addition to creating framework extension classes, you can create custom interfaces that all of your components can implement by default. This section considers an example for an application module, however, the same functionality is possible for a custom extended view object and view row interface as well.

Note: The examples in this section refer to the CustomizedExtensionInterface project in the AdvancedExamples workspace. See the note at the beginning of this chapter for download instructions.

Assume that you have a CustomApplicationModuleImpl class that extends ApplicationModuleImpl and that you want to expose two custom methods like this:

public void doFeatureOne(String arg);
public int anotherFeature(String arg);

Perform the following steps to create a custom extension interface CustomApplicationModule and have your CustomApplicationModuleImpl class implement it.

1. Create a custom interface that contains the methods you would like to expose globally on your application module components. For this scenario, that interface would look like this:

   package devguide.advanced.customintf.fwkext;
   /**
    * NOTE: This does not extend the
    * ====  oracle.jbo.ApplicationModule interface.
    */
   public interface CustomApplicationModule  {
     public void doFeatureOne(String arg);
     public int anotherFeature(String arg);
   }
   
   

   Notice that the interface does not extend the oracle.jbo.ApplicationModule interface.

2. Modify your CustomApplicationModuleImpl application module framework extension class to implement this new CustomApplicationModule interface.

   package devguide.advanced.customintf.fwkext;
   import oracle.jbo.server.ApplicationModuleImpl;
   public class CustomApplicationModuleImpl
          extends ApplicationModuleImpl 
          implements CustomApplicationModule {
     public void doFeatureOne(String arg) {
       System.out.println(arg); 
     }
     public int anotherFeature(String arg) {
       return arg == null ? 0 : arg.length();
     }
   }
   
   

3. Rebuild your project.

   The ADF wizards will only "see" your interfaces after they have been successfully compiled.

Then, to create a new ProductModule application module which exposes the global extension interface CustomApplicationModule and is based on the CustomApplicationModuleImpl framework extension class, do the following:

1. Ensure that your application module has a custom Java class.

   If it doesn't, you can enable one on the Java page of the Application Module Editor and clicking the Apply button.

2. Select CustomApplicationModuleImpl as the base class for the application module.

   To do this, again use the Java tab of the Application Module Editor and open the Extends dialog by clicking the Class Extends button.

3. Indicate that you want the CustomApplicationModule interface to be one of the custom interfaces that clients can use with your component.

   To do this, open the Client Interface page. Click on the Interfaces button. Shuttle the CustomApplicationModule interface from the Available to the Selected list, then click OK.

4. Insure that at least one method appears in the Selected list on the Client Interface page.

   
   

   Note: You need to select at least one method in the Selected list on the Client Interface page, even if it means redundantly selecting one of the methods on the global extension interface. Any method will do in order to get JDeveloper to generate the custom ProductModule interface.

   
   

When you dismiss the Application Module editor, JDeveloper generates the application module custom interface ProductModule. It automatically extends both the base ApplicationModule interface and your CustomApplicationModule extension interface like this:

package devguide.advanced.customintf.common;
import devguide.advanced.customintf.fwkext.CustomApplicationModule;

import oracle.jbo.ApplicationModule;
// ---------------------------------------------------------------------
// ---    File generated by Oracle ADF Business Components Design Time.
// ---------------------------------------------------------------------
public interface ProductModule
       extends CustomApplicationModule, ApplicationModule {
  void doSomethingProductRelated();
}

Once you've done this, then client code can cast your ProductModule application module to a CustomApplicationModule interface and invoke the generic extension methods it contains in a strongly-typed way.

Note: The basic steps are the same for exposing methods on a ViewObjectImpl framework extension class, as well as for a ViewRowImpl extension class.