Tips on Porting your Code to 3.0

Networks

Attributes

Views

Constructors

Spring

• The Spring config files is where all object initialization occurs.
• There are two spring config files:

  • src/main/resources/META-INF/spring/bundle-context.xml

    • This file constructs all "beans" (objects) for this bundle.
    • This file uses references created in bundle-context-osgi.xml to outside services.
    • This file instantiates the "beans" (objects) that are then used to declare services for other bundles to use.

  • src/main/resources/META-INF/spring/bundle-context-osgi.xml

    • This file connects this bundle to the OSGi world which means two things:
    • it creates references that can be used by this bundle from Services provided by other bundles
    • it declares services itself.

• The rule is to keep bundle-context.xml free of any OSGi semantics so that it can be used in a normal spring context and then put all OSGi related XML in bundle-context-osgi.xml.

OSGi

• OSGi impacts the design of Cytoscape, but its APIs are totally hidden through the use of Spring-DM. You should never reference OSGi APIs in your java code. This should all be handled in the Spring XML config files.

• The central concept in OSGi to be aware of is that of a Service.

  • A Service is defined by a java interface. Any valid java interface can be a service.

  • An implementation of this service is simply and implementation of its interface.
  • Access to the service is provided through a service registry.

  • In practice, however, this is all handled by Spring. You do not need to worry about the service registry in your java code!

• From the perspective of the Java developer, a Service is provided in one of two ways:
  1. As an argument to your object's constructor (i.e. it is injected).

  2. Mulitple instances of a service can also be injected into methods in a class. You simply define two methods, an add and a remove method with a signature that includes the interface and a Map of properties:

     • addService( MyServiceInterface s, Map props );

     • removeService( MyServiceInterface s, Map props );

     • These are normal methods in all respects.
     • The Spring xml is configured so that these methods get called when new services are registered or when old services are removed.