Diploma Thesis Santiago Gómez Sáez - IAAS

2.5. OSGi Framework
cycle management, addition, and monitoring and control of the components conforming to
the environment defined by the JBI specification.
2.5. OSGi Framework
The OSGi framework provides loose coupling between modules in a Java environment.
It provides a strong support for module versioning and third party modules referencing.
The OSGi defines a framework for deployment support in a Java Virtual Machine (JVM)
of downloaded or extended resources known as bundles. This framework requires OSGifriendly
devices a minimum system’s resources usage by providing dynamic code-loading
and bundle lifecycle management. An OSGi bundle is the packaging of a group of Java classes
and required and provided capabilities’ meta-data as a JAR file for providing functionality to
end users, which can be exposed as bundle services or just run internal processes. A valid
OSGi bundle can be installed in any valid OSGi container due to the standardized packaging
and bundle management.
OSGi bundles can be downloaded, extended and installed remotely or locally in the platform
when needed without the need of system reboot. Installation and update of bundles during
their lifecycle are also managed by the framework, which uses a service registration for
selection, update notifications, or registry of new service objects offered by a deployed bundle.
This feature is the main key for connecting bundles whose’s services require during runtime
capabilities provided by another bundles. The framework defines a bundle’s requirement
capability as a dependency.
The OSGi framework defines 5 different layers and a bundle’s lifecycle [OSG11]. An optional
Security Layer provides the infrastructure for deploying and managing applications which
must be controlled during runtime. The Module Layer lists the rules for package sharing
between the deployed bundles. The lifecycle of a bundle can be modified during runtime
through an API provided in the lifecycle layer. The main operations implemented are install,
update, start, stop or uninstall.
Apache ServiceMix 4.3.0 is built on and OSGi-based runtime kernel, which provides a
lightweight container that enables the deployment of various bundles [RD09]. Its architecture
and functionalities are described in the following section.
2.6. Apache ServiceMix
In this diploma thesis we extend a multi-tenant aware version of Apache ServiceMix 4.3.0,
referred to it in this document as ServiceMix. Essl evaluates different available ESB solutions
in the market, and as output of his work provides a selection decision for extending ServiceMix
in order to support multi-tenancy [Ess11]. As mentioned in Section 2.3, a multi-tenant ESB
solution in a PaaS environment must support tenant-aware communication, and tenant-aware
administration and management. The support is provided by Muhler and Gomez in their
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