Apache Axis2 - OSGi Integration in WSO2 Carbon Platform Sameera Jayasoma Technical Lead and Product Manager WSo2 Inc.

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Outline Apache Axis2 OSGi, the dynamic module system WSO2 Carbon SOA Platform Axis2 – OSGi Integration Problems faced Solutions Benefits

Apache Axis2 It is extensible. A Web Services Engine. Java runtime for hosting Web Services. Runs standalone or in conjunction with Application servers such as Apache Tomcat. Supports both SOAP and REST It is extensible.

OSGi Dynamic module system for Java platform Defines a way to create true modules and a way to interact at runtime. Modules(Bundles) in OSGi can be installed, updated and uninstalled without restarting the JVM. Benefits of OSGi, Improved time to market, Reduced development cost.

Bundle The unit of modularization in OSGi Traditional Java app. is a collection of Jars. But an OSGi based system is a collection of bundles. Bundle is just a JAR with some additional metadata(manifest headers) in the MANIFEST.MF file A java package is the unit of information hiding.

Bundles And Java Packages Bundles can share packages with other bundles or hide packages. Bundles can declare dependencies on java packages exported by other bundles

Bundles And Java Packages Bundle A Exported Packages Private Packages Imported Packages Bundle B Bundle C Imports

Life Cycle of a Bundle

OSGi Services Mechanism for bundles to collaborate at runtime. A service is a plain old Java object(POJO) published in OSGi service registry OSGi services provides in-VM SOA model for bundles

WSO2 Carbon A component based Service Oriented Architecture(SOA) platform for developing enterprise SOA middleware. Based on OSGi, provides a well define component model. Hence it allows you to create highly customized and optimized SOA applications to suit your enterprise. Base platform for all the Java products in WSO2.

WSO2 Carbon Based Products

Axis2 – OSGi Integration

Motivation Facilitate using Axis2 in OSGI based environments Improved class loading mechanism for deployed services and other Axis2 extensions such as Modules. Deploying Web services in Bundles Deploying Axis2 Extensions(Modules, Service Deployers, etc.) in Bundles.

Problems Faced Existence of split packages among axis2 jar files Dependencies of Axis2 are not yet available as OSGi bundles. Modules are required to be deployed before Web services in Axis2.

One Big Bundle Axis2 consists of several application jar files and third party libraries. axis2-kernal.jar axis2-adb.jar and many more.. Some Java packages are split among these jar files. org.apache.axis2.util package is available in both axis2- kernal.jar and axis2-adb.jar. A package can only be exported by a single bundle, if the version is same. Solution: Bundled all these axis2 jar files into single Big Bundle.

Carbon Orbit Bundles This Axis2 bundle still needs other third party libraries in the form of bundles to properly function in an OSGi environment. Most of these libraries were not available as bundles. Hence Carbon orbit project was initiated to wrap these libraries to OSGi bundles.

Web Services In Bundles Implemented a custom Service Deployer to handle Web services reside in Bundles. Used OSGi Extender pattern to detect the list of bundles which has Web services. BundleListeners are used listen to bundle events. Only the bundles in ACTIVE state are taken into consideration. Bundle classloader is set as the Service classloader to provide a better class loading mechanism for Web Services.

Axis2 Extensions In Bundles Extensions such as Axis2 Modules, Service Deployers, etc. in bundles are required to be deployed in Axis2. Here also, OSGi extender pattern is used. Bundles specify a custom manifest header. Axis2Deployer: POJODeployer Axis2Module: rampart Filter the list of bundles having Axis2 extensions using the manifest headers.

Modules Before Services Problem: In Axis2, modules should be deployed before services. Otherwise services become faulty and also these faulty services cannot be recovered. In OSGi, bundle starting order is unpredictable. Hence bundles with Axis2 Services may become ACTIVE before bundles with Axis2 Modules. Possibility of services being deployed before modules. Solution: Implements a faulty services recovery mechanism in Axis2.

Benefits of OSGi Integration OSGi has been accepted as the de facto standard which defines a dynamic modular system for Java. Major software vendors are moving to OSGi. Enables Axis2 to be used in any OSGi based applications, not just in WSO2 Carbon. Helps to increase its market share as a Web Services Engine.

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