The question if the spec packages should be included in the impl bundles
or not is highly disputed. See:
http://felix.apache.org/documentation/tutorials-examples-and-presentations/apache-felix-osgi-faq.html
Before karaf 4 I recommended to people to embed the api packages that
are implemented in the impl bundle.
In karaf 4 though this can cause severe problems. The reason is that the
new resolver will refresh bundles if optional dependencies are satisfied.
An example was the aries transaction manager bundle. It embedded the jta
api packages but also had an optional dependency on spring.
So when you first installed the transaction feature the transaction
manager bundle was started. If you then install a spring feature the
transaction manager bundle is refreshed.
If it contains the jta api this causes all bundles to be refreshed too
that import the jta api packages. So this can cause a lot of bundles to
be restarted. Sometimes such refreshs cascaded to cause refreshs of
almost all bundles. This causes quite some instability .. especially if
not all user bundles are written to work with arbitrary restarts.
A similar case was pax jdc and the osgi jdbc spec package.
So what I did with transaction manager and some other cases is to deploy
the api packages spearately and remove the api packages from the impl
bundles. This reduced the karaf refresh a lot and made the system much
more usable.
In many cases it is still ok to embed the api packages needed but if you
have any optional dependencies you should deploy the api in a separate
bundle.
As it is sometimes difficult to know if you will have optional
dependencies I now tend to always deploy the apis on their own.
Christian
On 29.02.2016 18:49, David Jencks wrote:
As far as I’m concerned, these little bundles are there to make it easier for
implementers of a particular spec to include that spec’s api in their
implementation bundle. It doesn’t do you any good to include the api without
an implementation at runtime. Thus, I think the quote below is highly
misleading.
david jencks
On Feb 29, 2016, at 9:20 AM, Markus Rathgeb <[email protected]> wrote:
FYI
"But what if you want to use the APIs at runtime? To support using the
APIs at runtime, OSGi has now made the companion code for individual
specifications available as individual companion code bundles."
http://blog.osgi.org/2015/08/more-jars-on-maven-central-and-jcenter.html
2016-02-29 8:40 GMT+01:00 Achim Nierbeck <[email protected]>:
Hi
it's a bad practice to provide the compendium or core osgi bundles, as those
contain far more packages then required.
Usually the services implementing those apis should provide the implemented
services. As can be seen for eventadmin,
configuration admin service and the http service in karaf.
regards, Achim
2016-02-28 22:15 GMT+01:00 Daniel McGreal <[email protected]>:
Hi Karaf users!
Installing the Compendium in a feature, e.g. with the following primitive
example, restarts the console, because dependent bundles refresh to wire
against it.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<features xmlns="http://karaf.apache.org/xmlns/features/v1.3.0";
name="cmpn">
<feature name="cmpn" description="cmpn"
version="2.5.0.BUILD-SNAPSHOT">
<bundle>mvn:org.osgi/org.osgi.compendium/5.0.0</bundle>
</feature>
</features>
This is causing me some problems, for example, after the shell restart
feature:(un)install commands result in an NPE.
java.lang.NullPointerException
at
org.apache.karaf.features.internal.region.SubsystemResolver.resolve(SubsystemResolver.java:216)[9:org.apache.karaf.features.core:4.0.4]
at
org.apache.karaf.features.internal.service.Deployer.deploy(Deployer.java:263)[9:org.apache.karaf.features.core:4.0.4]
at
org.apache.karaf.features.internal.service.FeaturesServiceImpl.doProvision(FeaturesServiceImpl.java:1089)[9:org.apache.karaf.features.core:4.0.4]
at
org.apache.karaf.features.internal.service.FeaturesServiceImpl$1.call(FeaturesServiceImpl.java:985)[9:org.apache.karaf.features.core:4.0.4]
at
java.util.concurrent.FutureTask.run(FutureTask.java:266)[:1.8.0_60]
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)[:1.8.0_60]
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)[:1.8.0_60]
at java.lang.Thread.run(Thread.java:745)[:1.8.0_60]
Is there a way to prevent this from happening?
Best, Dan.
--
Apache Member
Apache Karaf <http://karaf.apache.org/> Committer & PMC
OPS4J Pax Web <http://wiki.ops4j.org/display/paxweb/Pax+Web/> Committer &
Project Lead
blog <http://notizblog.nierbeck.de/>
Co-Author of Apache Karaf Cookbook <http://bit.ly/1ps9rkS>
Software Architect / Project Manager / Scrum Master
--
Christian Schneider
http://www.liquid-reality.de
Open Source Architect
http://www.talend.com
