how can I be notified when a bundle throws an exception in osgi runtime? (equinox helios)

Question

If a bundle throws an exception in osgi, the stack-trace is printed on the osgi console. I want to be notified if a bundle throws an exception. I thought using osgi logging service could help about it. However I could not get it to work under Helios.

• The question is how can I be notified if a bundle throws an exception in osgi Helios.

• Or if osgi logging does the work, how can I get osgi logging to work in Helios? As much as I googled, there is apparently no implementation of osgi loggin service currently integrated in helios. I downloaded the equinox skd 3.6 from eclipse site that contains the bundle org.eclipse.equinox.log, however I could add it as dependency to my plugins, or install it in the osgi runtime.

Any help is really appreciated.

Answer 1

A bundle can only throw an exception when it is invoked. This nearly always when some other bundle invoked one of your published services, or because the bundle received a callback from the framework such as BundleActivator.start().

In the first case, OSGi has absolutely no way to know that an exception happened! Service invocations are direct method calls between two objects, and are not brokered or proxied by the OSGi framework. Therefore if you want to find out about the exception, you must catch it in the calling code.

In the second case, callbacks happen because some bundle caused them to happen. For example, a bundle will be started because some other bundle called Bundle.start(). In this case, an exception thrown from the BundleActivator.start() method would be wrapped in a BundleException that could be caught by the calling code.

So it's really all down to your code, unless you have some third-party bundles that invoke your services or start/stop your bundles (e.g. a web console, or a shell like GoGo). In this case it's down to the third party code. In most cases they should send messages to the LogService, so you should install the log bundle into your framework.

You said that you couldn't install the log bundle, but you didn't say why it failed, what the error message was etc! This kind if information is important if you want help resolving the problem.

Answer 2

You could try Pax Logging and a custom Log4J appender - Pax Logging provides implementations of the OSGi LogService etc as well as wrappers for common logging frameworks.

Do you want to do this purely to log/notify exceptions, or is there some other reason? An UncaughtExceptionHandler might be what you want if it's a case of managing your own or wrapped code.