Require a service to be active before a bundle is started

I have written a BundleActivator which should update certain configurations before its bundle starts. I need the ConfigurationAdmin service, but I get a null ServiceReference from the BundleContext in the start method of the BundleActivator.

The BundleActivator extends following abstract class and only implements the specific update logic:

public abstract class AbstractConfigUpdater implements BundleActivator

private ServiceReference<ConfigurationAdmin> configurationAdminServiceReference;

@Override
public void start(final BundleContext context) throws Exception
configurationAdminServiceReference = context.getServiceReference(ConfigurationAdmin.class);
final ConfigurationAdmin configurationAdmin = context.getService(configurationAdminServiceReference);
final Configuration configurations =
configurationAdmin.listConfigurations(getFilter());
if (configurations != null)
for (final Configuration configuration : configurations)
final Dictionary<String, Object> properties = configuration.getProperties();
if (updateProperties(properties))
configuration.update(properties);





protected abstract String getFilter();

/**
* Updates the properties if needed.
*
* @param properties
* the configuration properties
* @return if any modifications to the Dictionary were made
*/
protected abstract boolean updateProperties(final Dictionary<String, Object> properties);

@Override
public void stop(final BundleContext context) throws Exception
context.ungetService(configurationAdminServiceReference);





I have added an annotation to the concrete BundleActivator to generate a manifest header to require the ConfigurationAdmin service to be available to the bundle:

@RequireCapability(filter = "(objectClass=org.osgi.service.cm.ConfigurationAdmin)",
ns = "osgi.service",
resolution = Resolution.mandatory)


The manifest header is generated, but I still get a null ServiceReference. How should I fix this? Or is there an alternative approach I could take to update configurations before their components are started?

2 Answers
2

I don't know if this could help, but you can develop a org.osgi.service.cm.ConfigurationPlugin to intercept all the properties that are injected at runtime and modify them:

org.osgi.service.cm.ConfigurationPlugin

public class MyConfigurationPlugin implements BundleActivator, ConfigurationPlugin
ServiceRegistration<ConfigurationPlugin> configPluginRef;

@Override
public void start(BundleContext context) throws Exception
//... init the config plugin
Map<String,String> properties = new HashMap<>();
configPluginRef = context.registerService(
ConfigurationPlugin.class,
this,
new Hashtable<>(properties));


@Override
public void modifyConfiguration(ServiceReference<?> reference,
Dictionary<String, Object> properties)
/*
* View and possibly modify a set of configuration properties
* before they are sent to the Managed Service or the Managed Service Factory.
*/





Of course the Declarative Service approach is a way far simpler option:

@Component (
service= ,
configurationPid=
configPid1,
configPid2,
...
)
public class MyComponent

@Activate
public void activate(BundleContext context, Map<String, String> properties)



@Modified
public void updated(BundleContext context, Map<String, String> properties)
// Called when properties change




but in this case you cannot alter properties values: you can only react to properties changes.

You can use OSGi ServiceTracker to wait and retrieve the service from the service registry.

For example,

import org.osgi.framework.Constants
import org.osgi.framework.Filter;
import org.osgi.util.tracker.ServiceTracker;
import org.osgi.service.cm.ConfigurationAdmin;

...

private static final long TIMEOUT_MILLIS = 10000;

@Override
public void start(final BundleContext context) throws Exception
Filter filter = context.createFilter("(" + Constants.OBJECTCLASS + "=org.osgi.service.cm.ConfigurationAdmin)");
ServiceTracker<?, ?> configurationAdminTracker = new ServiceTracker<>(context, filter, null);

configurationAdminTracker.open();
ConfigurationAdmin configurationAdmin = (ConfigurationAdmin) configurationAdminTracker.waitForService(TIMEOUT_MILLIS);
configurationAdminTracker.close();

if (configurationAdmin == null)
// Not found

...



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