OSGi Development

EclipseRT in Indigo Release Train: Equinox

For some years Eclipse has been based on OSGi Bundles, aka Plug ins. OSGi is provided by Eclipse Equinox and not only runs the IDE, but also all Eclipse Runtime Environments.

What's new with the Indigo Release (Eclipse 3.7)?

Equinox supports OSGi 4.3


The newest OSGi Specification 4.3 was released in April 2011 and Eclipse Equinox already supports this – just a few weeks later. Isn't this fast ?

 

OSGi R4.3 Core Framework API Updates: OSGi now supports generics – some of you have waited for this for a long time ;-) ServiceRegistry, ServiceTracker, BundleTracker and Bundle Interface – generics are now possible everywhere. OSGi has to support J2ME 1.1 and J2SE 1.4 – and yes, it's still working. For J2ME platforms the OSGi API is compiled in a way that allows to continue running on J2SE 1.4. Of course this also works using Equinox.

 

Hint: some packages now are deprecated:

 

org.osgi.service.packageadmin

org.osgi.service.startlevel


and are replaced by these packages:

 

org.osgi.framework.wiring

org.osgi.framework.startlevel


Good news also for all fans of bytecode-weaving – the manipulating of bytecode at runtime. There's a new weaving hook“ available:

 

org.osgi.framework.hooks.weaving


Now it's even possible to change package dependencies on-the-fly – a powerful but also dangerous tool.

Equinox and Logging


OSGi is a very flexible framework, but its also easy to use many different logging frameworks by independent projects: Log4J, SLF4J, java.util etc. Many times last year, I opened bugzillas because some projects declared a required-bundle dependency for logging frameworks. This isn't a good idea if you have to use projects together and want to get all log events into one framework. In the meantime, the situation has become much better: most projects are using package-imports instead and so it's easy to use one framework like SLF4J, for supporting them all. I'm also glad to notice, that more and more projects are now using SLF4J together with Logback as native implementation – that's also the way I'm going to solve this.

 

Besides the 'legacy' logging there's also logging from OSGI framework (Equinox) and also Eclipse (IDE). It was difficult to use all these API's together: ILog, FrameworkLog, OSGi LogService. Indigo makes it easier, because Equinox Extended OSGi LogService now is part of the core framework. It doesn't matter where the log events are produced – now listeners can watch them all. If you want to know more about “logging and OSGi here's a detailed blog series.

Jetty Webserver Now with Version 7


Perhaps you don't already know, but under the umbrella of Eclipse RT there's a high grade webserver – Jetty. OSGi already includes a HTTP Server – but I recommend to use a full featured one like Jetty.

 

Some packages are renamed for Jetty 7 and some of the upcoming Servlet 3.0 features are already provided. Using Jetty and Equinox, it's really easy to build an OSGi webserver without writing web.xml and deploying as war:

 

Of course you can use Jetty the normal WebApp way, too ;-)

EclipseLink: Version 2.3.0 with Powerful Enhancements


Server applications are alway hungry for data, so you have to think how to persist them. EclipseLink was a part of release train for the first time in 2009 (same as Riena) and the project has made good progress since then.

 

EclipseLink covers three different parts:

 

In this article I'm only looking at JPA. Two or three years ago I used Hibernate in my customer projects as an ORM Framework. Hibernate is powerful, but has many dependencies and is also not a good OSGi citizen, so it's painful to integrate.

 

You can use EclipseLink in SE, EE or OSGi Environments. Also EclipseLink was used by the Gemini Project to provide a JPA module.

 

Who doesn't know this: the server is up and running with many users, but one department really needs some more properties added to Entities. Using EclipseLink 2.3.0 you can do this on-the-fly. Previously, PersistenceUnits in running applications couldn't be changed – but EclipseLink 2.3.0 now allows the user to refresh the EntityManagers in running applications.

 

Next enhancement: Mappings can be stored and changed externally. EclipseLink 2.3.0 allows the user to store MetaDataSource external to the running application. Together with the on-the-fly Extending of Entities you get more dynamicity and flexibility. Kudos to the team! You can read about all N&N from the eclipseLink project here.

Gyrex Server


Gyrex is one of the new projects this year. Gyrex promises to ease the development of scalable (even clustered) Equinox-based servers. At the last JAX conference in May in Germany, I listened to Gunnar Wagenknecht's Session and was impressed.

 

 

Gyrex is based on Equinox and Jetty, uses p2 as provisioning engine, RAP as Admin – UI and allows integration into the Cloud.

Update Target Platform


If you're already developing software for different targets, then you have to know the Target Platform definitions. Using Target Platform Definitions you build your Target Platform from update sites, directories etc. to be used by your product. Using a Target Platform is easy – the way to develop the target platform could be difficult. Usually it takes some time until you find out which Software Sites you have to contact and which features you really need.

 

A really big problem was maintaining target platforms - how to survive plugin updates. There was nothing like Update” and everything had to be done manually. Now the pain has an end: Target Platforms can be updated – for single software items, or all. There's a button added to Target Platform definition Editor:

 

 

If no updates are available, the Target Platform remains unchanged. Hint: make a copy of your definition before updating.

RTP – another new RT Project


Now we know it's easier to update and maintain Target Platforms. But it's still not easy to start and to define the Target Platform for the first time. This is where the new Runtime Packaging Project (RTP) will help you. RTP will provide predefined Runtime Packages for common scenarios.

 

 

RTP Packages can be installed using download and run as stand-alone projects using a script, or via update-site used as an entry point to define your platform. Thanks also to the RTP Team, they have collected all the information on how to install and configure Target Platforms for most of the many Runtime Projects. Now it should be easy to find the right entry point. http://eclipse.org/rtp/examples/ should be part of the bookmark list for all Runtime developers.

Prospect


If you now want to try out some EclipseRT projects or find out how to deal with target platforms, Kai Tödter has provided an easy-to-follow demo using Equinox and Jetty together with Vaadin as UI. enMOcs also is a pure Equinox / Jetty based server to communicate between Enterprise and mobile devices.

 

Some more interesting server projects at EclipseRT are Virgo and Gemini. Gemini provides EE Modules under OSGi, supporting the complete lifecycle. Virgo started as SpringSource dm Server and eases the development of Spring-powered EE- and Web Application Servers under OSGi. You see there are many different servers available at EclipseRT – try them out and if none fits your requirements, build your own.

 

In the next (4th) part of my series, I will cover DVCS - Distributed Version Control Systems. We'll take a look at Git / EGit and MercurialEclipse. EGit has finally reached 1.0 and next year more and more Eclipse projects will jump over to EGit.

 

Check out part one and part two of Ekkehard Gentz's Indigo Highlights, for even more info on the Eclipse release.

Ekkehard  Gentz
Ekkehard Gentz

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