Time for action – adding logging

The OSGi platform defines a LogService which allows messages to be logged to a central collector. In the E4 platform, an instance of LogService is available as part of the platform, routing error messages through to the console.

1. Open the Hello class and add a private field LogService logService.

2. Add an @Inject annotation to the LogService field.

3. In the create method, add a call to the log service.

4. The Hello class will look like:

   import javax.inject.Inject;
   import org.osgi.service.log.LogService;
   public class Hello {
     @Inject
     private LogService logService;
     @PostConstruct
     public void create(Composite parent) {
       label = new Label(parent, SWT.NONE);
       label.setText("Hello");
       logService.log(LogService.LOG_ERROR, "Hello");
     }
     ...
   }

5. Run the application, and a log message will be printed out to the console of the host Eclipse:

   !ENTRY org.eclipse.e4.ui.workbench 4 0 2016-06-02 13:36:42.381
   !MESSAGE Hello
   

What just happened?

The E4 runtime infrastructure...