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Equinox Application Model Demo
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
- 1 The Projects
- 2 Running using the application selector GUI
- 3 Running using the headless application
- 4 How it Works
The projects for the demo are stored in the Equinox Incubator (http://git.eclipse.org/c/equinox/rt.equinox.incubator.git/). All projects are under the directory demos/app-model/.
A prebuilt version of the demo is available here.
This project provides a simple RCP application that uses the application admin service to manage the other applications installed on the platform.
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
Running using the application selector GUI
Applications can be run using the application selector GUI or directly from the OSGi console. The application selector is an RCP application included in the org.eclipse.equinox.examples.app.selector bundle. Since the selector is 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:
- The application name
- If the application is enabled.
- The application state (inactive, starting, running, stopping)
To start the application selector use the Eclipse Application launch configuration called demoAppSelector. This launch configuration is included in the org.eclipse.equinox.examples.app.selector project.
To launch an application, select it in the application selector UI then use the context menu to run the start operation. Note that the start action is disabled if the application state is not currently inactive. Once running the UI should show the application as running and the application should appear disabled. The application is disabled (i.e., no longer available for launch) because all applications in this demo have a cardinality of 1 meaning that only one instance can be running at at time. Try launching other applications at the same time. You should be able to run one instance of all enabled applications.
To stop an application, select it in the application selector then use the stop context menu operation. Note that stop is disabled if the application state is currently inactive. Once the application is stopped you should notice that it moves to the inactive state.
Stop the Application Selector
If the application selector is stopped while one or more of the example SWT applications are running then it stops all of them before exiting the application selector. this is not quite accurate currently. Exiting the app selector leaves all applications running
Running using the headless application
Applications can also be launched and managed using a headless mechansim and the OSGi console. The headless application sets up a shared display for the example SWT applications to use. This application is provided by the org.eclipse.equinox.examples.sharedisplay bundle. The fact that it is headless allows it to run with a minumum set of bundles but of course you 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.
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 launches the application.
osgi> startApp org.eclipse.swt.examples.paint.app Launched application: org.eclipse.swt.examples.paint.app
You should notice that the application moves to disabled state indicating that it is no longer available for launch. Again, 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. Again, you should be able to run one instance of each application at the same time.
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.
osgi> stopApp org.eclipse.swt.examples.paint.app Stopped application: org.eclipse.swt.examples.paint.app
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. need to verify this
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.
- The application ID
- The application Name
- The application Cardinality. How many instances of the application can be running at the same time
- What thread must the application run on.
- 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.
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
- Query properties of an installed application using the getProperties method. For example, if the application is enabled.
- Launch the application using the launch method.
- Schedule a condition to launch the application using the schedule method.
- Lock an application using the lock method.
- 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.