Andreas you are crossing or about to cross a bridge we are crossing at the
moment. We also have a SpringDM based application. It is 3+ years in
production and so a change as large as moving away from SpringDM is very
disruptive. For the most part we considered only Aries Blueprint vs DS.
However as you can see from this post there are other alternatives, some
fairly recent such as support for Spring namespaces in Aries Blueprint. 

For us the most significant points to consider were

1) Will there still be good support in 5-10 years (having been burnt once we
don't want face the same issue again)

2) Where is the general OSGi community heading? Blueprint/DS/other. The
first sentence of Tim Ward's post is something we thought significant.
Something that has concerned me over the last couple of years is sometimes
an alternative is suggested by needs some jiggery pokery to make it work, it
doesn't have wide support, little documentation, often has bugs which led to
a churn of releases. While it may be a cool, clever solution we aren't going
to bet our production system on cool and clever only.

3) We are by and large glue coders and don't have the ability nor want to
spend the time/resource building our own custom  solutions, this is where I
think Spring has suited us well until now. We tried to identify what
offerings were available for the bits we needed e.g. JPA, JDBC,
transactional control, Camel JMS, CXF. It is an opinion only, but from what
I could see Blueprint offered the broadest support (see Christian's
ecosystems-compared
http://www.slideshare.net/mfrancis/osgi-ecosystems-compared-on-apache-karaf-christian-schneider).
 

The big one for us was lack of JPA/JDBC/transactional control for DS, while
there were some solutions we wanted something with a 'spec behind it'. This
is currently been worked on at the moment
(https://github.com/apache/aries/tree/trunk/tx-control) and I think it is a
significant piece of work that will make DS a much more attractive
proposition in the enterprise/applications space. Admittedly there is a risk
in being new adopter however we think the risk is worth it in this case.
Camel has a recent DS offering camel-scr (although I think there are some
issues with it). Hopefully in time more libraries will offer DS support out
of the box.

4) We are not yet sure we will be able to fully realise the pros of the
service dynamics that DS offers vs Blueprint as although one of our goals is
to be able to 'hot swap' bundles into a running system this may be harder to
achieve than we had hoped. We currently do some limited hot swapping with
our SpringDM system.

5) Perhaps counter intuitively of less importance to us was the actual ease
of transition, Blueprint would almost certainly be easier to migrate to from
SpringDM but we think that this is a one off cost that will be outweighed in
the long term.

Tim





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