ObjektSpektrum-Article on Agility & Architecture

Together with my colleague Stefan Roock I wrote an article on building architectures in an agile way for the current issue of the German ObjektSpektrum magazine. The article is part of a controversy with Thomas Lieder about how to incrementally build architectures in agile projects.

In the introductory part of the controversy we talk about the basics of agile methods and the goal of keeping a flat cost curve for features over a long period of time. To achieve this goal we need to change and refactor the software all the time. This is an integral part of agile software development. We learned that its not possible to foresee the future and therefore decided to design only the next steps - and refactor, if we learn over time and find better designs if new requirements appear. This is quite clear on the low-level of individual classes and nicely supported by test-driven development and refactoring tools.

If we use the same argumentation for the architecture of a project, the discussions get a lot more controversy. People don't believe that it is easy to change and refactor the architecture of a system incrementally and flexible over time. We found this discussion often times quite unstructured and using the term architecture in various flavors and meanings. To ease the discussion about agile architectures we divide between the basic architectural style and the concrete architecture of a concrete system. Our opinion is that the basic architectural style is hard to change over time (for example changing a system from a standalone-rich-client application into a multi-user app-server-based system could be quite hard). In contrast to this we believe that changing the concrete architecture and structure of a system could be done incrementally and agile over time. This is obviously not true for every application. They need to be build from ground-up for flexibility and change. But how to build a system that is easier to change over time, even on the architectural level?

From our point of view, there are three fundamental characteristics of design you need to remember every day to build flexible architectures: understandable, loosely coupled and free of redundance. There are many well-known design principles that helps you to build such systems. Keep them in mind, build loosely coupled components, think about good APIs between them - and you are on the right track to build flexible applications and flexible architectures.

Together with my colleague Stefan Roock I wrote an article on building architectures in an agile way for the current issue of the German ObjektSpektrum magazine. The article is part of a controversy with Thomas Lieder about how to incrementally build architectures in agile projects.

In the introductory part of the controversy we talk about the basics of agile methods and the goal of keeping a flat cost curve for features over a long period of time. To achieve this goal we need to change and refactor the software all the time. This is an integral part of agile software development. We learned that its not possible to foresee the future and therefore decided to design only the next steps - and refactor, if we learn over time and find better designs if new requirements appear. This is quite clear on the low-level of individual classes and nicely supported by test-driven development and refactoring tools.

If we use the same argumentation for the architecture of a project, the discussions get a lot more controversy. People don't believe that it is easy to change and refactor the architecture of a system incrementally and flexible over time. We found this discussion often times quite unstructured and using the term architecture in various flavors and meanings. To ease the discussion about agile architectures we divide between the basic architectural style and the concrete architecture of a concrete system. Our opinion is that the basic architectural style is hard to change over time (for example changing a system from a standalone-rich-client application into a multi-user app-server-based system could be quite hard). In contrast to this we believe that changing the concrete architecture and structure of a system could be done incrementally and agile over time. This is obviously not true for every application. They need to be build from ground-up for flexibility and change. But how to build a system that is easier to change over time, even on the architectural level?

From our point of view, there are three fundamental characteristics of design you need to remember every day to build flexible architectures: understandable, loosely coupled and free of redundance. There are many well-known design principles that helps you to build such systems. Keep them in mind, build loosely coupled components, think about good APIs between them - and you are on the right track to build flexible applications and flexible architectures.

ObjektSpektrum-Article on Agility & Architecture

Incremental Design at SEACON 2009

A few days ago I gave a short talk on Incremental Design at SEACON 2009, a new buzzword-free conference in Hamburg, Germany. Aside of the fact that this was the first conference in my beautiful home town (and only 15min away from home), I enjoyed to meet a lot of people there. I also made up a few slides for my talk, which you can now download as PDF (in German):

• Inkrementeller Entwurf (pdf)

And last but not least I used my new presentation tool called Session Five for the first time. Was absolutely great!

A few days ago I gave a short talk on Incremental Design at SEACON 2009, a new buzzword-free conference in Hamburg, Germany. Aside of the fact that this was the first conference in my beautiful home town (and only 15min away from home), I enjoyed to meet a lot of people there. I also made up a few slides for my talk, which you can now download as PDF (in German):

• Inkrementeller Entwurf (pdf)

And last but not least I used my new presentation tool called Session Five for the first time. Was absolutely great!

Incremental Design at SEACON 2009

"OSGi on the Server"-Talk at JAOO 2009 in Aarhus

I am invited to the JAOO 2009 conference in Aarhus, Denmark, to talk in the “Java-Now” track about “OSGi on the Server”. I am pretty excited to join the folks at JAOO since I heard a lot of good things about this conference and the program already sounds quite interesting. Hope to meet a lot of interesting people there!

I am invited to the JAOO 2009 conference in Aarhus, Denmark, to talk in the “Java-Now” track about “OSGi on the Server”. I am pretty excited to join the folks at JAOO since I heard a lot of good things about this conference and the program already sounds quite interesting. Hope to meet a lot of interesting people there!

"OSGi on the Server"-Talk at JAOO 2009 in Aarhus

Slides from the OSGi Talks at Java User Group Essen

Already two weeks ago I gave two talks together with Gerd Wütherich at the Java User Group Essen meeting at May 14th. We talked about OSGi in general and building web applications on top of OSGi in specific. We had a room full of interested people and I enjoyed a lot talking there. If you are interested in the slides, here they are:

• OSGi Service Platform by Example (pdf, in german)
• Mit OSGi Web-Anwendungen entwickeln (pdf, in german)

Enjoy!

Already two weeks ago I gave two talks together with Gerd Wütherich at the Java User Group Essen meeting at May 14th. We talked about OSGi in general and building web applications on top of OSGi in specific. We had a room full of interested people and I enjoyed a lot talking there. If you are interested in the slides, here they are:

• OSGi Service Platform by Example (pdf, in german)
• Mit OSGi Web-Anwendungen entwickeln (pdf, in german)

Enjoy!

Slides from the OSGi Talks at Java User Group Essen

OSGi Talks at Java User Group Essen

I will be at the Java User Group Essen meeting next week to talk about OSGi together with my colleague Gerd Wütherich. We will talk about the basic ideas behind OSGi as well as building web applications on top of OSGi. Take a look at the announcement for more details (in German).

I will be at the Java User Group Essen meeting next week to talk about OSGi together with my colleague Gerd Wütherich. We will talk about the basic ideas behind OSGi as well as building web applications on top of OSGi. Take a look at the announcement for more details (in German).

OSGi Talks at Java User Group Essen

Coming up: Eclipse Demo Camp in Hamburg

The tradition of the Eclipse Demo Camps in Hamburg (Germany) will continue with its next edition on Monday, May 25. We will, again, be at the scenic EAST design hotel and have great demos, drinks and, and, and... So don't forget to register yourself by adding your name to the Galileo Demo Camp Hamburg wiki page. This time, we had the idea to continue with a Stammtisch right after the Demo Camp (please don't forget to add your name to that list as well), so even more drinks can follow... ;-)

The tradition of the Eclipse Demo Camps in Hamburg (Germany) will continue with its next edition on Monday, May 25. We will, again, be at the scenic EAST design hotel and have great demos, drinks and, and, and... So don't forget to register yourself by adding your name to the Galileo Demo Camp Hamburg wiki page. This time, we had the idea to continue with a Stammtisch right after the Demo Camp (please don't forget to add your name to that list as well), so even more drinks can follow... ;-)

Coming up: Eclipse Demo Camp in Hamburg

Equinox Aspects 1.0 M7a available for download

Because of a stupid bug in the caching area I put a fixed build of the milestone online. So if you tried M7 and observed performance problems with the caching, you should try this fixed milestone build instead from the Equinox Aspects download area.

Because of a stupid bug in the caching area I put a fixed build of the milestone online. So if you tried M7 and observed performance problems with the caching, you should try this fixed milestone build instead from the Equinox Aspects download area.

Equinox Aspects 1.0 M7a available for download

Equinox Aspects 1.0 M7 available for download

The seventh milestone of Equinox Aspects is available for download from the Equinox Aspects download page. This milestone contains quite a large improvement for controlling the weaving of bundles. More details can be found in this comment on bug 255682. Take also a look at the New & Noteworthy list for 1.0M7 on the web to find out more.

The seventh milestone of Equinox Aspects is available for download from the Equinox Aspects download page. This milestone contains quite a large improvement for controlling the weaving of bundles. More details can be found in this comment on bug 255682. Take also a look at the New & Noteworthy list for 1.0M7 on the web to find out more.

Equinox Aspects 1.0 M7 available for download

Building a Lego Castle Incrementally and Interatively

My colleagues Henning Wolf and Arne Roock had a great idea for our company booth at the last JAX conference: Every attendee got a single LEGO brick in his conference pocket. The goal was to jointly build a LEGO castle at the booth, piece by piece, with a huge crowd of developers. So every attendee got a time slot of 30 seconds (a single iteration) to place one or more bricks and/or to refactor the existing building. And we had (and I think the builders, too) a lot of fun with that! Its always fun to work with these creative guys!

Arne and Marcel recorded a stop-motion-movie from the building process, taking a picture after each 30-seconds iteration. The final movie is published at the companies website:

• Stop motion movie: it-agile and the LEGO Experiment at JAX

Have fun watching the movie!

My colleagues Henning Wolf and Arne Roock had a great idea for our company booth at the last JAX conference: Every attendee got a single LEGO brick in his conference pocket. The goal was to jointly build a LEGO castle at the booth, piece by piece, with a huge crowd of developers. So every attendee got a time slot of 30 seconds (a single iteration) to place one or more bricks and/or to refactor the existing building. And we had (and I think the builders, too) a lot of fun with that! Its always fun to work with these creative guys!

Arne and Marcel recorded a stop-motion-movie from the building process, taking a picture after each 30-seconds iteration. The final movie is published at the companies website:

• Stop motion movie: it-agile and the LEGO Experiment at JAX

Have fun watching the movie!

Building a Lego Castle Incrementally and Interatively

JAX 2009 Revisited

My colleague and friend Matthias Lübken wrote with me a short blog-kind-of-a review, reflecting the JAX conference in Mainz last week. Just some thoughts and impressions on OSGi, Scala, Pecha Kucha (and more...) for the next Eclipse-Magazin. The online version is already available here:

• JAX-2009-Comments and Thoughts
  

But take care, its German... ;-)

My colleague and friend Matthias Lübken wrote with me a short blog-kind-of-a review, reflecting the JAX conference in Mainz last week. Just some thoughts and impressions on OSGi, Scala, Pecha Kucha (and more...) for the next Eclipse-Magazin. The online version is already available here:

• JAX-2009-Comments and Thoughts
  

But take care, its German... ;-)

JAX 2009 Revisited

Load-Time Weaving for Spring-DM

Load-time weaving in an OSGi environment is different than in single-classpath-settings like you often have in Java. There you typically use a JVM agent or a specialized classloader that gets ClassFileTransformer components injected from your application. Those ClassFileTransformer components then to the real job of modifying bytecode at load-time. This is also used in the Spring framework to enable aspect weaving or JPA bytecode enhancements.
This gets different when you are working in an OSGi environment. Within OSGi you no longer have a single classpath application, you cannot (or at least should not) create specialized classloaders for yourself to do the magic, maybe the weaving should happen specifically for each bundle or the woven code gets additional dependencies woven into it. Using Spring in an OSGi environment doesn't make things easier. You can use Spring Dynamic Modules to implement really cool OSGi applications, but your Spring load-time weaving support remains broken to some degree (see all the related questions in the Spring-DM forum).
I often thought about using Equinox Aspects to solve these problems. Since Equinox Aspects is not tightly bound to AspectJ weaving only, you could re-use the base infrastructure to hook any kind of bytecode modifier into the Equinox runtime - and reuse the caching of Equinox Aspects at the same time.

Now I have a first sketch implemented that bridges between Spring-LTW and Equinox Aspects. The EquinoxAspectsLoadTimeWeaver class implements the LoadTimeWeaver interface of Spring and can therefore be used in your spring context as the load-time weaver component:

<context:spring-configured>
<context:annotation-config>
<context:load-time-weaver
  class="org.eclipse.equinox.weaving.springweaver.EquinoxAspectsLoadTimeWeaver"/>

If you define this load-time weaver your bundle need to define an Import-Package on "org.eclipse.equinox.weaving.springweaver", of course.

To use this kind of load-time weaver definition to need to add "org.eclipse.equinox.weaving.hook" (from Equinox Aspects) to your target platform as well as "org.eclipse.equinox.weaving.springweaver":

• org.eclipse.equinox.weaving.springweaver_0.1.1.zip
  

When you launch your OSGi runtime you need to set the system property: (osgi.framework.extensions=org.eclipse.equinox.weaving.hook) and start the springweaver bundle right at startup. You can do this by adding it to the config.ini file (org.eclipse.equinox.weaving.springweaver@4:start). This is basically the same when using Equinox Aspects, except that you no longer start org.eclipse.equinox.weaving.aspectj but instead the springweaver bundle.

There are still some issues that need to be solved (see this comment in the spring forum for details), but I hope to can try it out and tell me what works fine and what needs some more work.

Feedback always welcome! Enjoy!

Load-time weaving in an OSGi environment is different than in single-classpath-settings like you often have in Java. There you typically use a JVM agent or a specialized classloader that gets ClassFileTransformer components injected from your application. Those ClassFileTransformer components then to the real job of modifying bytecode at load-time. This is also used in the Spring framework to enable aspect weaving or JPA bytecode enhancements.
This gets different when you are working in an OSGi environment. Within OSGi you no longer have a single classpath application, you cannot (or at least should not) create specialized classloaders for yourself to do the magic, maybe the weaving should happen specifically for each bundle or the woven code gets additional dependencies woven into it. Using Spring in an OSGi environment doesn't make things easier. You can use Spring Dynamic Modules to implement really cool OSGi applications, but your Spring load-time weaving support remains broken to some degree (see all the related questions in the Spring-DM forum).
I often thought about using Equinox Aspects to solve these problems. Since Equinox Aspects is not tightly bound to AspectJ weaving only, you could re-use the base infrastructure to hook any kind of bytecode modifier into the Equinox runtime - and reuse the caching of Equinox Aspects at the same time.

Now I have a first sketch implemented that bridges between Spring-LTW and Equinox Aspects. The EquinoxAspectsLoadTimeWeaver class implements the LoadTimeWeaver interface of Spring and can therefore be used in your spring context as the load-time weaver component:

<context:spring-configured>
<context:annotation-config>
<context:load-time-weaver
  class="org.eclipse.equinox.weaving.springweaver.EquinoxAspectsLoadTimeWeaver"/>

If you define this load-time weaver your bundle need to define an Import-Package on "org.eclipse.equinox.weaving.springweaver", of course.

To use this kind of load-time weaver definition to need to add "org.eclipse.equinox.weaving.hook" (from Equinox Aspects) to your target platform as well as "org.eclipse.equinox.weaving.springweaver":

• org.eclipse.equinox.weaving.springweaver_0.1.1.zip
  

When you launch your OSGi runtime you need to set the system property: (osgi.framework.extensions=org.eclipse.equinox.weaving.hook) and start the springweaver bundle right at startup. You can do this by adding it to the config.ini file (org.eclipse.equinox.weaving.springweaver@4:start). This is basically the same when using Equinox Aspects, except that you no longer start org.eclipse.equinox.weaving.aspectj but instead the springweaver bundle.

There are still some issues that need to be solved (see this comment in the spring forum for details), but I hope to can try it out and tell me what works fine and what needs some more work.

Feedback always welcome! Enjoy!

Load-Time Weaving for Spring-DM

JAX 2009: Patterns and Best Practices for Dynamic OSGi Applications

Right after the talk on my lessons learned I had the pleasure to talk together with Kai Tödter and Gerd Wütherich about examples, patterns and some best practices to build real dynamic OSGi applications. Here are the slides:

• Patterns and Best Practices for Dynamic OSGi Applications (pdf)
  

Kai put together a really nice example for using different ways on how to build dynamics into OSGi apps. It demonstrates all the cool ways of dealing with OSGi services in a declarative way, like Declarative Services, iPojo, Spring Dynamic Modules and Guice/Peaberry. The URL to the example project is on slide 7, if you would like to take a closer look at it.

Right after the talk on my lessons learned I had the pleasure to talk together with Kai Tödter and Gerd Wütherich about examples, patterns and some best practices to build real dynamic OSGi applications. Here are the slides:

• Patterns and Best Practices for Dynamic OSGi Applications (pdf)
  

Kai put together a really nice example for using different ways on how to build dynamics into OSGi apps. It demonstrates all the cool ways of dealing with OSGi services in a declarative way, like Declarative Services, iPojo, Spring Dynamic Modules and Guice/Peaberry. The URL to the example project is on slide 7, if you would like to take a closer look at it.

JAX 2009: Patterns and Best Practices for Dynamic OSGi Applications

JAX 2009: Lessons Learned from 5 Years of Building Enterprise OSGi Applications

Yesterday I gave a talk at JAX 2009 about my experiences from using OSGi for enterprise application development over the past 5 years. I tried to sum up my experiences and most of all the mistakes I made during the past years using OSGi. If you are interested, take a look at the slides:

• Lessons Learned: 5 Years of Building Enterprise OSGi Applications (pdf)

Enjoy - and try to not make the same mistakes than I... ;-)

Yesterday I gave a talk at JAX 2009 about my experiences from using OSGi for enterprise application development over the past 5 years. I tried to sum up my experiences and most of all the mistakes I made during the past years using OSGi. If you are interested, take a look at the slides:

• Lessons Learned: 5 Years of Building Enterprise OSGi Applications (pdf)

Enjoy - and try to not make the same mistakes than I... ;-)

JAX 2009: Lessons Learned from 5 Years of Building Enterprise OSGi Applications

JAX 2009: What's Possible for Web-Apps and OSGi

Today I gave a presentation together with Gerd Wütherich and Peter Roßbach about the difficulties and options you have if you want to adopt OSGi for building web applications. The room was pretty crowded (more than 220 people) and I enjoyed the talk a lot. If you would like to take a look at the slides, you can find them here (unfortunately in German):

• Mit OSGi Web-Anwendungen entwickeln - Was geht, was nicht? (pdf)

Enjoy!

Today I gave a presentation together with Gerd Wütherich and Peter Roßbach about the difficulties and options you have if you want to adopt OSGi for building web applications. The room was pretty crowded (more than 220 people) and I enjoyed the talk a lot. If you would like to take a look at the slides, you can find them here (unfortunately in German):

• Mit OSGi Web-Anwendungen entwickeln - Was geht, was nicht? (pdf)

Enjoy!

JAX 2009: What's Possible for Web-Apps and OSGi

JAX 2009: What's New in Equinox Aspects

Today I gave an updated version of my EclipseCon short talk on What's New In Equinox Aspects at the Eclipse Forum Europe 2009, here in Mainz. Here are the slides:

• What's New in Equinox Aspects (pdf)

Enjoy!

Today I gave an updated version of my EclipseCon short talk on What's New In Equinox Aspects at the Eclipse Forum Europe 2009, here in Mainz. Here are the slides:

• What's New in Equinox Aspects (pdf)

Enjoy!

JAX 2009: What's New in Equinox Aspects

Next version of Scala IDE for Eclipse uses Equinox Aspects

Today Miles Sabin posted details on the upcoming 2.7.4 release of the Scala IDE for Eclipse. I am pretty excited about the fact that it uses Equinox Aspects to implement deeper integration with JDT. It uses the same aspect bundle as AJDT called JDT weaving. Andrew Eisenberg gave a great talk on JDT weaving at EclipseCon 2009. Take a look at the slides if you would like to read more about JDT weaving using Equinox Aspects.

Today Miles Sabin posted details on the upcoming 2.7.4 release of the Scala IDE for Eclipse. I am pretty excited about the fact that it uses Equinox Aspects to implement deeper integration with JDT. It uses the same aspect bundle as AJDT called JDT weaving. Andrew Eisenberg gave a great talk on JDT weaving at EclipseCon 2009. Take a look at the slides if you would like to read more about JDT weaving using Equinox Aspects.

Next version of Scala IDE for Eclipse uses Equinox Aspects

EclipseCon 2009: OSGi for Eclipse Developers

It was fun giving the talk on "OSGi for Eclipse Developers" at EclipseCon 2009 together with Chris Aniszczyk and Bernd Kolb. At the end we had plenty of time for some interesting questions. Luckily we had BJ Hargrave and Peter Kriens sitting in the first row to answer the really hard ones... :-)

Here are the slides of the talk:

• OSGi for Eclipse Developers (pdf)

It was fun giving the talk on "OSGi for Eclipse Developers" at EclipseCon 2009 together with Chris Aniszczyk and Bernd Kolb. At the end we had plenty of time for some interesting questions. Luckily we had BJ Hargrave and Peter Kriens sitting in the first row to answer the really hard ones... :-)

Here are the slides of the talk:

• OSGi for Eclipse Developers (pdf)

EclipseCon 2009: OSGi for Eclipse Developers

EclipseCon 2009: What's New in Equinox Aspects

Just a few minutes ago I finished my short talk on "What's New in Equinox Aspects" at EclipseCon 2009. The slides are online:

• What's New in Eqiunox Aspects (pdf)

I am now looking forward to my talk tomorrow on "OSGi for Eclipse Developers" together with Chris and Bernd. Stay tuned!

Just a few minutes ago I finished my short talk on "What's New in Equinox Aspects" at EclipseCon 2009. The slides are online:

• What's New in Eqiunox Aspects (pdf)

I am now looking forward to my talk tomorrow on "OSGi for Eclipse Developers" together with Chris and Bernd. Stay tuned!

EclipseCon 2009: What's New in Equinox Aspects

Exciting OSGi-Experts-Day at JAX 2009

Just a few weeks after the upcoming EclipseCon the next conference opens the doors. The JAX conference (which also includes the Eclipse Forum Europe) in Germany takes place in Mainz, Germany, from April 20th to 24th. While the conference is fully packed with a lot of interesting stuff, I had the honor to organize the OSGi Experts Day, a one-day mini conference inside JAX. The goal of this extra day at the end of the JAX week is to have advanved topics only and nothing for OSGi newbies.

Of course I had more ideas how to fill this day that slots available, but I think we will have a quite interesting day. These six talks will be presented:

• Peter Kriens on Puzzled about Java Modularity
• Richard Hall on Coming soon to OSGi - Standard framework launching and composite bundles!
• Doug Clarke and Shaun Smith on OSGi Persistence
• Heiko Seeberger and Roman Roelofsen on Scala Modules - Ease the OSGi development with a Scala DSL
• Ekkehard Gentz on Building an OSGi-based EJB3 Server
• Stephan Herrmann on Bundle reuse and adaptation with Object Teams: Don't settle for a compromise!

At the end all speakers will participate in a panel to answer questions from the audience. And I am sure that we will have a lot of interesting discussions during the breaks as well. So join us for this cool day on advanced OSGi topics!

Just a few weeks after the upcoming EclipseCon the next conference opens the doors. The JAX conference (which also includes the Eclipse Forum Europe) in Germany takes place in Mainz, Germany, from April 20th to 24th. While the conference is fully packed with a lot of interesting stuff, I had the honor to organize the OSGi Experts Day, a one-day mini conference inside JAX. The goal of this extra day at the end of the JAX week is to have advanved topics only and nothing for OSGi newbies.

Of course I had more ideas how to fill this day that slots available, but I think we will have a quite interesting day. These six talks will be presented:

• Peter Kriens on Puzzled about Java Modularity
• Richard Hall on Coming soon to OSGi - Standard framework launching and composite bundles!
• Doug Clarke and Shaun Smith on OSGi Persistence
• Heiko Seeberger and Roman Roelofsen on Scala Modules - Ease the OSGi development with a Scala DSL
• Ekkehard Gentz on Building an OSGi-based EJB3 Server
• Stephan Herrmann on Bundle reuse and adaptation with Object Teams: Don't settle for a compromise!

At the end all speakers will participate in a panel to answer questions from the audience. And I am sure that we will have a lot of interesting discussions during the breaks as well. So join us for this cool day on advanced OSGi topics!

Exciting OSGi-Experts-Day at JAX 2009

Slides from OOP talk on dynamics with OSGi available

As Kai Tödter already pointed out in his blog entry, our session on dynamics for OSGi applications at the OOP conference last week was a lot of fun. I enjoyed this session with Kai and Gerd a lot. Thanks, guys!

• Best practices for dynamic OSGi applications (slides as pdf)

As Kai Tödter already pointed out in his blog entry, our session on dynamics for OSGi applications at the OOP conference last week was a lot of fun. I enjoyed this session with Kai and Gerd a lot. Thanks, guys!

• Best practices for dynamic OSGi applications (slides as pdf)

Slides from OOP talk on dynamics with OSGi available