Blueprint

From OSGi Community Wiki

The Blueprint Service is a way of instantiating and consuming services provided by others by means of an external XML configuration file. It is similar in intent to Declarative Services.

Contents 1 Configuration 2 Spring 3 Differences with Declarative Services 4 References

Configuration

The following is an example of a blueprint service, which is stored in OSGI-INF/blueprint/*.xml

<components xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"> 
  <description>Optional description for the blueprint defined in this file.</description>
  <component id="my.example.component" class="com.example.Class">
  </component>
</components>

Spring

The Blueprint service is heavily inspired by the Spring Framework.

Differences with Declarative Services

A key difference between the Blueprint Service and Declarative Services is when the instantiation of components appear. With Blueprint, the components are created as soon as the bundle is loaded; if there are any dependent services that are not present, there is a proxy which is bound and defers dynamically when a service becomes available. If a service is not present, calls to the proxy will hang until one is available.

Declarative Services, on the other hand, will not create a component until all of its dependent services are available.

References

• Building OSGi applications with Blueprint