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Equinox Application Model Demo

Revision as of 22:40, 28 February 2007 by Jeff-bugs.code9.com (Talk | contribs)

The Eclipse platform implements an application container that is based on the OSGi Application Admin Service specification. This demo shows how Eclipse applications can be managed using the OSGi Application Admin Service specification

The Projects

The projects for the demo are stored in the Equinox Incubator on the main Eclispe CVS repository (dev.eclipse.org:/cvsroot/eclipse). All projects are under the directory equinox-incubator/demos/app-model/.

org.eclipse.equinox.examples.app.selector

This project provides a simple RCP application that uses the application admin service to manage the other applications installed on the platform.

org.eclipse.equinox.examples.sharedisplay

This project provides a simple headless application that sets up a shared display that other applications can share when they are launched.

example SWT applications

Each of the following projects provide an example SWT application that can be launched using the application admin service

  • org.eclipse.swt.examples.addressbook
  • org.eclipse.swt.examples.browserexample
  • org.eclipse.swt.examples.clipboard
  • org.eclipse.swt.examples.graphics
  • org.eclipse.swt.examples.paint

Running using the application selector GUI

This approach launches an RCP application called application selector. This application is provided by the org.eclipse.equinox.examples.app.selector project. Since this approach uses an RCP application many other bundles are required to run. For example, the org.eclipse.ui.workbench and all of its dependencies. The application selector displays the following information about each SWT example application installed on the platform:

  1. The application name
  2. If the application is enabled.
  3. The application state (inactive, starting, running, stopping)

To start the application selector use the Eclipse Application launcher called demoAppSelector. This launcher is included in the org.eclipse.equinox.examples.app.selector project.

Start an Application

Select an application to start from the application selector then use the context menu to run the start operation. Note that the start operation will be disabled if the application state is not currently inactive. This will cause the application to launch. You should notice the state of the application move to running and the application will become disabled. Disabled indicates that the application is no longer available for launch. This is because all applications in this demo have a cardinality of 1. Try launching other applications at the same time. You will be able to launch all applications that are enabled at the same time.

Stop an Application

Select an application to stop from the application selector then use the context menu to run the stop operation. Note that the stop operation will be disabled if the application state is currently inactive. This will cause the application to stop. You should notice the state of the application move to inactive.

Stop the Application Selector

If the application selector is stopped while one or more of the example SWT applications are running then it will stop all of them before exiting the application selector.

Running using the headless application

This approach launches a headless application which sets up a shared display for the example SWT applications to use. This application is provided by the org.eclipse.equinox.examples.sharedisplay project. This approach does not use an RCP application which allows it to run with a minumum set of bundles. Since there is no UI available to control applications we must use the osgi> console commands provided by the org.eclipse.equinox.app bundle to start and stop the applications.

To start the application selector use the OSGi Framework launcher called equinoxShareDisplay. This launcher is included in the org.eclipse.equinox.examples.sharedisplay project.

Start an Application

To see a list of applications run the apps console command

osgi> apps
org.eclipse.swt.examples.paint.app [enabled]
org.eclipse.swt.examples.graphics.app [enabled]
org.eclipse.swt.examples.addressbook.app [enabled]
org.eclipse.equinox.examples.sharedisplay.application [disabled]
org.eclipse.equinox.app.error [disabled]
org.eclipse.swt.examples.browserexample.app [enabled]
org.eclipse.swt.examples.clipboard.app [enabled]

Pick an application id to start and run the startApp command. This will cause the application to launch.

osgi> startApp org.eclipse.swt.examples.paint.app
Launched application: org.eclipse.swt.examples.paint.app

You should notice the application becomes disabled. Disabled indicates that the application is no longer available for launch. This is because all applications in this demo have a cardinality of 1.

osgi> apps
org.eclipse.swt.examples.paint.app [disabled]
org.eclipse.swt.examples.graphics.app [enabled]
org.eclipse.swt.examples.addressbook.app [enabled]
org.eclipse.equinox.examples.sharedisplay.application [disabled]
org.eclipse.equinox.app.error [disabled]
org.eclipse.swt.examples.browserexample.app [enabled]
org.eclipse.swt.examples.clipboard.app [enabled]

Try launching other applications at the same time. You will be able to launch all applications that are enabled at the same time.

Stop an Application

To see a list of active applications run the activeApps console command

osgi> activeApps
org.eclipse.equinox.examples.sharedisplay.application [running]
org.eclipse.swt.examples.paint.app [running]

Pick an application id to stop and run the stopApp command. This will cause the application to stop.

osgi> stopApp org.eclipse.swt.examples.paint.app
Stopped application: org.eclipse.swt.examples.paint.app

Stop the Headless Share Display Application

If the headless application is stopped while one or more of the example SWT applications are running then it will stop all of them before exiting the headless application.

How it Works

The applications extension point

Each application is declared using the org.eclipse.core.runtime.applications extension point. A bundle can declare an org.eclipse.core.runtime.applications extension to define an application in their plugin.xml file. An application extension is used to declare the following characteristics about an application.

  1. The application ID
  2. The application Name
  3. The application Cardinality. How many instances of the application can be running at the same time
  4. What thread must the application run on.
  5. What class provides the application implementation (IApplication)

The following is the Address Book application extension

<extension
  id="app"
  name="Address Book"
  point="org.eclipse.core.runtime.applications">
  <application
    cardinality="1"
    thread="any">
    <run
     class="org.eclipse.swt.examples.addressbook.Application">
    </run>
  </application>
</extension>

This extension defines the Address Book application and specifies that it can only have 1 instance running at a time and can run on any thread. It is important that it runs on any thread because in the demo the driving applications (the Application Selector or the Headless Application) are run on the main thread. This is necessary so that an SWT Display can be created and the SWT Event loop can be started on the main thread by the driving applications. All other applications are launched using separate threads and share the display created by the driving application.

ApplicationDescriptor Services

For each application extension defined the Eclipse application container registers an ApplicationDescriptor service (org.osgi.service.application.ApplicationDescriptor). This service can be used to perform the following operations

  1. Query properties of an installed application using the getProperties method. For example, if the application is enabled.
  2. Launch the application using the launch method.
  3. Schedule a condition to launch the application using the schedule method.
  4. Lock an application using the lock method.
  5. Unlock an application using the unlock method.

When an application is launched an ApplicationHandle is returned and is registered as a service. The ApplicationHandle can be used to stop an application using the destroy method.