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Equinox/p2/Helios Migration Guide

< Equinox‎ | p2
Revision as of 11:23, 25 January 2010 by John (Talk | contribs) (Switch from global OSGi services to agent-specific services)

In the Helios release p2 graduated much of its provisional API into stable, real API. This page provides some guidance to users of the old provisional p2 API on how to migrate to the mature API in the Helios release.

Pervasive changes

Switch from global OSGi services to agent-specific services

In the Ganymede and Galileo releases, p2 services were registered as global OSGi services. This style made it difficult to support multiple instances of p2 services operating in the same framework instance at the same time. The p2 API now uses an approach where services are obtained from a provisioning agent instance rather than directly from the OSGi registry. This means code like this:

 ServiceReference ref = bundleContext.getServiceReference(IEngine.class.getName());
 IEngine engine = (IEngine)bundleContext.getService(ref);

Is now replaced by code like this:

 IProvisioningAgent agent = ...;//get the agent you want to work with
 IEngine engine = (IEngine) agent.getService(IEngine.SERVICE_NAME);

For details on how to obtain an agent, see the Multiple Agents documentation.

Metadata changes


IRequiredCapability was limiting in what it could express. For example it could not express negation and or'ing, and it could only described dependencies on something that had a namespace, a name and a version and we are striving to express requirements and capabilities on other things (for example BundleExecutionEnvironment). As such, to ensure for API evolution we have turned the too specific IRequiredCapability into an IRequirement.

Query changes


CapabilityQuery from the provisional API has been deleted in favor of expressions. Thus the former:

 IRequiredCapability cap = ...;
 new CapabilityQuery(cap);

Can be written as:

 IRequirement cap = ...;
 new ExpressionQuery(IInstallableUnit.class, cap.getMatches());

Or, using Java 5 generics:

 IRequirement cap = ...;
 new ExpressionQuery<IInstallableUnit>(IInstallableUnit.class, 



There is currently no direct API replacement for IUPropertyQuery, but the equivalent query can be performed using an expression query:

 new ExpressionQuery<IInstallableUnit>(IInstallableUnit.class,
    ExpressionUtil.parse("properties[$0] == $1"), "foo", "true");

The above will match all IInstallableUnits with a "foo" property whose value is "true".

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