Time for action – creating a simple service

POJOs can be instantiated and made available in the E4 context, such that they can be injected into other classes or created on demand. This allows an application to be built in a flexible manner without tight coupling between services.

1. Create a class StringService in the com.packtpub.e4.application package with a @Creatable annotation, and a process method that takes a string and returns an uppercase version:

   import org.eclipse.e4.core.di.annotations.Creatable;
   @Creatable
   public class StringService {
     public String process(String string) {
       return string.toUpperCase();
     }
   }

2. Add an injectable instance of StringService to the Rainbow class:

   @Inject
   private StringService stringService;

3. Use the injected stringService to process the color choice before posting the event to the event broker:

   public void selectionChanged(SelectionChangedEvent event) {
     IStructuredSelection sel = (IStructuredSelection)
      event.getSelection();
     Object colour...