>>>>> Tatu Saloranta <[email protected]>:
> The reason Jackson components are defined to be released as bundles is
> because AFAIK that is what is required for proper functioning within OSGi
> container. I was under impression this is not true for regular jars,
> although relevant metadata can of course be included under META-INF/MANIFEST
All that OSGi containers care about is that what it loads have the
format of a jar file with a META-INF/MANIFEST.MF that contains the
headers required for an OSGi bundle.
Creating an OSGi compliant MANIFEST.MF can be accomplished in various
ways
1. Adding the headers manually using the <manifestEntries>
configuration of the maven-jar-plugin (a lot of work and kind of
fragile, but I've seen it used)
2. Using the maven-bundle-plugin (the most common way)
3. Interactively in the eclipse MANIFEST.MF editor (possibly how most
of the eclipse bundles are created...?)
4. By alternatives to the maven-bundle-plugin (I have seen some
mentioned earlier, but I was unable to google them up today, so I'm
guessing they are mostly dead)
Using the maven-bundle-plugin to create an OSGi compliant MANIFEST.MF
can be done, by:
1. Using <packaging>bundle</packaging> (what jackson does)
2. Using <supportedProjectTypes> in the maven-bundle-plugin config, to
make it run on jar projects (what I do)
3. Binding maven-bundle-plugin to a phase in the maven build (not
commonly done anymore)
As for actually loading the bundle into the OSGi runtime there are
various ways
1. Earlier versions of the eclipse target platform consisted of a
directory containing jar files with names based on the
bundle-symbolic-name (an OSGi MANIFEST.MF header), and the version
(a regular MANIFEST.MF header)
2. Current versions of the eclipse target platfom consist of XML files
defining what jar files should be loaded as OSGi bundles
3. Apache Karaf has a heap of ways of getting bundles into the OSGi
runtime, off the top of my head, here are some of them:
1. Loading bundles interactively from the karaf console command
line, using the bundle's maven coordinates (maven central and a
couple of other apache repos are built-in to karaf, other maven
repos, eg. a local nexus installation can be configured in).
Here's an example of a karaf console bundle install, picked
completely at random...:-)
bundle:install
mvn:com.fasterxml.jackson.core/jackson-annotations/2.10.0
2. Loading bundles using features (this is a higher level
dependency resolution mechanism. To use an analogy: if bundles
are .deb packages, then karaf features are debian APT)
Both other feature files and bundles are referred to by maven
coordinates
3. Dropping bundles into a directory that karaf scan and then load
all jar files dropped into that directory
4. kar files, which are zip files containg an XML feature
definition and all jar files required by the feature file
(ie. it doesn't require access to a maven repository)
5. (there are more but the above are the ones I could remember)
As to the actual file type supported when loading bundles:
1. AFAIK all OSGi implementations support jar files with an OSGi
compliant MANIFEST.MF
2. karaf supports both jar files and war (web archive) files
3. earlier versions of the eclipse equinox OSGi runtime supported
"directory bundles" that are directories consisting of an unpacked
jar files
For playing around with loading OSGi bundles I recommend following the
karaf quick start guide (basically: download and unpack the most recent
karaf binary as a tar.gz or .zip file, cd-ing into the unpack directory
and running the command "bin/karaf")
https://karaf.apache.org/manual/latest/quick-start.html
The karaf console is the command line that opens when starting karaf
interactively (it's also possible to ssh into a running karaf and do the
same commands there).
commands to try
bundle:install (install a bundle by its maven coordinates)
feature:repo-add (install a karaf feature repository by its maven coordinates)
feature:install (install a feature by its name)
bundle:list (lists installed bundles)
bundle:capabilities (lists the OSGi capabilities of an installed bundle)
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