View
229
Download
3
Embed Size (px)
Citation preview
1
Why OSGi matters for Enterprise Java Infrastructures
Santosh Kumar
2
Agenda
• Introduction to OSGi
• Why is OSGi technology important
• How OSGi matters for Infrastructure
• OSGi Enterprise spec
• OSGi in Cloud
• Q&A
3
Take away from this session• Overall understanding to view OSGi as THE
module system for Java
• Understanding of what this OSGi Enterprise spec is all about
• Should be able to start experimenting with it themselves using one of the available implementations
OSGiKey for Infrastructure
4
What is OSGi
OSGi - Open Services Gateway initiative– Technology is the dynamic module system for
Java™.– Provides a service-oriented, component-based
environment for developers– Offers standardized ways to manage the software
lifecycle.– Support for building modular
dynamic and extensible systemsOSGi
Consider as Universal Middleware
5
Lets put things in perspective…
The Complexity & Scale of Software requires:
1. Service Oriented
As complexity and size increases Need for higher level of abstract programming
6
Why OSGi?2. Modularity
• Java Platform Modularity– Classes encapsulate data– Packages contain classes– Jars contain packages
• Class visibility:private, package private, protected,public
• No “jar scoped” access modifiers.• No means for a jar to declare its dependencies.• No versioning.• Jars have no modularization characteristics
– At runtime, global classpath to search
Jar as unit does not have modularity
7
Why OSGi?
3. Versioning– Enterprise Apps have isolated
classpaths but… – Across apps - each archive typically
contains all the libraries required by the application
Common libraries/frameworks get installed with each application
Multiple copies of libraries in memory
– Within apps - 3rd party libraries consume other libraries leading to version conflicts
p lankto n.v1
p lankto n.v2
8
Overall Architecture
= serviceHardware
Driver Driver Driver
Operating System
Java
OSGi
Fram
eworkModule (Bundle)
OSGi as module system
9
OSGi –The Dynamic Module System for Java
OSGi specifies a modular architecture for dynamic component based systems
• Execution Environment
• Module Layer
• Life Cycle Layer
• Service LayerOSGi introduces
Bundles
as modules
10
Module layer
• Bundle - unit of module
• Packaged as JAR - classes + manifest + resources
- Versioning support
- Dependency specification
- JAR with MIME type : application/vnd.osgi.bundle
• OSGi enforces modularity in bundles
Bundle as module represents separation of concerns
11
OSGi ClassLoading
• Each bundle has its own classloader / classpath. More efficient for large systems
• Multiple versions of bundles supported concurrently
12
Service Layer• Defines a publish/find/bind service model
– Fully dynamic– Intra VM– service registry
• A service is a normal Java object published under one or more Java interfaces with additional metadata with the service registry
• Bundles can register services, search for them, or receive notifications when their registration state changes.
• Service lifecycle is highly dynamic– Service may be published or unpublished at any time
13
Service Orientation
Service ProviderService Provider
Service RegistryService Registry
Service ConsumerService Consumer
Service Description
publish find
interact
OSGi intrinsically supports SOA
14
Life Cycle
• API to control the security and life cycle operations of bundles
• Install, uninstall, start, stop bundles dynamic without restarting applications
15
What does the OSGi Framework provide?
• Horizontal Software Integration Platform
• Component Oriented Architecture– Module (Bundles)
– Package sharing and version management
– Life-cycle management and notification (events)
• Service Oriented Architecture– Publish/find/bind intra-VM service model
– Life-cycle notification (events)
16
Framework Features• Runs multiple applications and services
• Single VM instance
• Separate class loader per bundle
– Class loader network
– Independent namespaces
– Class sharing at the Java package level
• Lifecycle management of bundles
• Intra VM publish/find/bind service model
• Java Permissions to secure framework
17
Where OSGi is used
• Equinox
– Reference implementation of core framework and various services
– Base runtime for all of Eclipse (rich client, server side and embedded)
• Felix - Ships with GlassFish
• Application servers : Websphere, JBoss etc
• SOA Virtualization Platform : TIBCO Active Matrix
widespread use in desktop and servers
18
Does Enterprise Java need OSGi?• Current challenges
– Lots of Libraries To Manage
– Designed for Extensibility
– Dynamic Deployment, Uptime
– Well-defined coherent modules
– Simplify unit of reuse
19
OSGI in Enterprise
• Integration of established Java Enterprise Edition technologies into an OSGi Environment
• Multiple, interoperable, dependency injection based component models
• Distributed service model for multiple service platforms and external heterogeneous systems
• Database persistence support
• Enterprise-class life cycle and configuration management
20
OSGi Enterprise Spec V4.2• Brings Enterprise technologies and OSGi together - OSGi
Enterprise Expert Group (EEG)
• Using existing Java SE/EE specifications:
– JTA, JPA, JNDI, JMX, WebApps, SCA
– Framework integrates with the Java EE programming model
• Adds Spring-derived component model and dependency injection container – Blueprint Container
Embeded Desktop Enterprise
21
What’s happening with OSGi EE
• Apache “Aries” - new Apache incubator project
– deliver set of pluggable Java components enabling an enterprise OSGi application programming model.
• Eclipse Enterprise Modules (“Gemini”)
– collection of subprojects, each of which is an implementation or integration of an enterprise-level technology
• Virgo - Dynamic Enterprise Application Platform
– provide a runtime platform for development of server-side enterprise applications
22
Blueprint Components and Service
• Specifies a Dependency Injection container, standardizing established Spring conventions
• Specifies components can be wired together within a bundle
• Components can be published as services to the service registry
• Components configuration and dependencies injected them Blueprint component container ( part of the runtime environment)
• Configuration and dependencies declared in XML “module blueprint”
23
Blueprint Components and Service
•Extended for OSGi: publishes and consumes components as OSGi services
• Blueprint standardizes the configuration metadata, and brings governance to the specification of the component model.
• Simplifies unit test outside either Java EE or OSGi r/t.
• The Blueprint DI container is a part of the server runtime (compared to Spring which is part of the application.)
dependencies injected
publishesservice
consumesservice
Blueprint managed bundle Blueprint managed bundle
Blueprint Components ( POJO)
24
The Java Persistence API• JPA is a POJO based Object Relational Mapping Framework
– defines an API for persisting
objects into a Relational Database
– API for retrieving Objects
from the database
• JPA - rich API for mapping
arbitrarily complex objects to the underlying database tables
25
The JPA Service Specification
An OSGi specification for making JPA work in an OSGi frameworkCore concepts:
> Persistence Bundle : An OSGi bundle containing managed classes a persistence descriptor and a Meta-Persistence manifest header
> Meta-Persistence header : – A header that defines the locations of persistence descriptors in a bundle
> EntityManagerFactory service : An EntityManagerFactory available as an OSGi service
> Persistence Client : A bundle that makes use of an EntityManagerFactory service.
> EntityManagerFactory builder : A factory for incomplete persistence units
26
Remote Services
• Extending the OSGi framework to configure existing distributed computing software systems
• Describes how to distribute OSGi services
• Ability for OSGi services to invoke services running in other JVMs
• Support enterprise application topologies for availability, reliability, and scalability
Enables Distributed OSGi
27
Web Applications Specification• Defines how to support the Servlet 2.5 and
JavaServer Pages (JSP) 2.1 specifications in OSGi
• Provide deployment of existing and new web applications to Servlet containers operating on the OSGi service platform
• Specification defines the Web Application Bundle, a bundle that performs the same role as the WAR in Java EE
28
Web Applications Specification• WAB uses the OSGi life cycle and class/resource loading rules
instead of the standard Java EE environment
• Details web application packaged as a WAR may be installed into an OSGi Service Platform
29
SCA Configuration
• Provides an assembly model for distributed applications and systems using a service oriented architecture
• Components that are assembled can be written in different technologies for example Java EE, BPEL, C++, and scripting languages
• Execute on different machines, and can communicate through different protocols and technologies
• Declarative application metadata to enable reflection of an SCA component type definition
30
SCA Configuration
• Remote Services specification provides an extendable model for configuration types
• SCA Configuration Type Specification defines such a configuration type
31
OSGi on CloudInvestigation underway to find possibility of using OSGi in the
context of cloud computing (RFP 133 Cloud Computing)
IaaSInfrastructure as a
Service
PaaSPlatform as a Service
SaaSSoftware as a Service
32
OSGi on Cloud
Value of OSGi : ability to address the following
- Dependency management
- Provisioning/Configuration (Remote services API)
- Extensible, modular system
- Dynamic replacement of components
33
Conclusion
Major Java infrastructures support OSGi modular approach
support apps designed & deployed as bundles
34
Summary
OSGiKey for Infrastructure OSGi
Consider as Universal Middleware
Bundle as module represents separation of concerns
OSGi increasingly relevant to Enterprise OSGi and Cloud
Synergy having interesting possibilities
35
References• http://www.eclipsezone.com/articles/extensions-vs-service
s/
• OSGi Core Spec
• OSGi Enterprise Spec
• http://www.osgi.org