DUE TO SPAM, SIGN-UP IS DISABLED. Goto Selfserve wiki signup and request an account.
...
Example
...
2
...
-
...
Dictionary
...
Service
...
Bundle
...
This
...
example
...
creates
...
a
...
bundle
...
that
...
implements
...
an
...
OSGi
...
service.
...
Implementing
...
an
...
OSGi
...
service
...
is
...
a
...
two-step
...
process,
...
first
...
we
...
must
...
define
...
the
...
interface
...
of
...
the
...
service
...
and
...
then
...
we
...
must
...
define
...
an
...
implementation
...
of
...
the
...
service
...
interface.
...
In
...
this
...
particular
...
example,
...
we
...
will
...
create
...
a
...
dictionary
...
service
...
that
...
we
...
can
...
use
...
to
...
check
...
if
...
a
...
word
...
exists,
...
which
...
indicates
...
if
...
the
...
word
...
is
...
spelled correctly
...
or
...
not.
...
First,
...
we
...
will
...
start
...
by
...
defining
...
a
...
simple
...
dictionary
...
service
...
interface
...
in
...
a
...
file
...
called
...
DictionaryService.java:
| Code Block |
|---|
/* * Apache Felix OSGi tutorial. **/ package tutorial.example2.service; /** * A simple service interface that defines a dictionary service. * A dictionary service simply verifies the existence of a word. **/ public interface DictionaryService { /** * Check for the existence of a word. * @param word the word to be checked. * @return true if the word is in the dictionary, * false otherwise. **/ public boolean checkWord(String word); } |
The
...
service
...
interface
...
is
...
quite
...
simple,
...
with
...
only
...
one
...
method
...
that
...
needs
...
to
...
be
...
implemented.
...
Notice
...
that
...
we
...
put
...
the
...
service
...
interface
...
in
...
the
...
package
...
tutorial.example2.service,
...
instead
...
of
...
just
...
putting
...
it
...
in
...
tutorial.example2.
...
We
...
did
...
this
...
because
...
we
...
need
...
to
...
share
...
the
...
interface
...
definition
...
with
...
other
...
bundles,
...
therefore
...
it
...
is
...
better
...
to
...
separate
...
service
...
interfaces
...
that
...
need
...
to
...
be
...
shared
...
from
...
code
...
that
...
does
...
not
...
need
...
to
...
be
...
shared.
...
Such
...
an
...
approach
...
ensures
...
a
...
strong
...
separation
...
between
...
interface
...
and
...
implementation.
...
In
...
the
...
following
...
source
...
code,
...
the
...
bundle
...
uses
...
its
...
bundle
...
context
...
to
...
register
...
the
...
dictionary
...
service.
...
We
...
implement
...
the
...
dictionary
...
service
...
as
...
an
...
inner
...
class
...
of
...
the
...
bundle
...
activator
...
class,
...
but
...
we
...
could
...
have
...
also
...
put
...
it
...
in
...
a
...
separate
...
file.
...
The
...
source
...
code
...
for
...
our
...
bundle
...
is
...
as
...
follows
...
in
...
a
...
file
...
called
...
Activator.java:
| Code Block |
|---|
/* * OSGiApache and Gravity Service Binder tutorial. * Copyright (c) 2003 Richard S. Hall * http://oscar-osgi.sourceforge.netFelix OSGi tutorial. **/ package tutorial.example2; import java.util.PropertiesHashtable; import org.osgi.framework.BundleActivator; import org.osgi.framework.BundleContext; import org.osgi.framework.ServiceListener; import org.osgi.framework.ServiceEvent; import tutorial.example2.service.DictionaryService; /** * This class implements a simple bundle that uses the bundle * context to register an English language dictionary service * with the OSGi framework. The dictionary service interface is * defined in a separate class file and is implemented by an * inner class. **/ public class Activator implements BundleActivator { /** * Implements BundleActivator.start(). Registers an * instance of a dictionary service using the bundle context; * attaches properties to the service that can be queried * when performing a service look-up. * @param context the framework context for the bundle. **/ public void start(BundleContext context) { PropertiesHashtable<String, String> props = new PropertiesHashtable<String, String>(); props.put("Language", "English"); context.registerService( DictionaryService.class.getName(), new DictionaryImpl(), props); } /** * Implements BundleActivator.stop(). Does nothing since * the framework will automatically unregister any registered services. * @param context the framework context for the bundle. **/ public void stop(BundleContext context) { // NOTE: The service is automatically unregistered. } /** * A private inner class that implements a dictionary service; * see DictionaryService for details of the service. **/ private static class DictionaryImpl implements DictionaryService { // The set of words contained in the dictionary. String[] m_dictionary = { "welcome", "to", "the", "osgi", "tutorial" }; /** * Implements DictionaryService.checkWord(). Determines * if the passed in word is contained in the dictionary. * @param word the word to be checked. * @return true if the word is in the dictionary, * false otherwise. **/ public boolean checkWord(String word) { word = word.toLowerCase(); // This is very inefficient for (int i = 0; i < m_dictionary.length; i++) { if (m_dictionary[i].equals(word)) { return true; } } return false; } } } |
Note
...
that
...
we
...
do
...
not
...
need
...
to
...
unregister
...
the
...
service
...
in
...
the
...
stop()
...
method,
...
because
...
the
...
OSGi
...
framework
...
will
...
automatically
...
do
...
so
...
for
...
us.
...
The
...
dictionary
...
service
...
that
...
we
...
have
...
implemented
...
is
...
very
...
simple;
...
its
...
dictionary
...
is
...
a
...
static
...
array
...
of
...
only
...
five
...
words,
...
so
...
this
...
solution
...
is
...
not
...
optimal
...
and
...
is
...
only
...
intended
...
for
...
educational
...
purposes.
...
We
...
must
...
create
...
a
...
manifest.mf
...
file
...
that
...
contains
...
the meta-data for our bundle;
...
the
...
manifest
...
file
...
contains
...
the
...
following:
| No Format |
|---|
Bundle-Activator: tutorial.example2.Activator Export-Package: tutorial.example2.service Bundle-Name: English dictionary Bundle-Description: A bundle that registers an English dictionary service Bundle-Vendor: RichardApache HallFelix Bundle-Version: 1.0.0 Bundle-Activator: tutorial.example2.Activator Export-Package: tutorial.example2.service Import-Package: org.osgi.framework |
We specify which class is used to activate our bundle via the Bundle-Activator attribute and also specify that our bundle exports a shared package using the Export-Package attribute. The Export-Package attribute makes it possible for other bundles to import our dictionary service interface. The Import-Package attribute informs the framework of the bundle's dependencies on external packages; all bundles with an activator must import org.osgi.framework since it contains the core OSGi class definitions. Any packages dependencies will be verified and resolved by the OSGi framework. (Note: Make sure your manifest file ends in a trailing carriage return or else the last line will be ignored.)
To compile our source code, we need the felix.jar file (found in Felix' bin directory) in our class path. We compile the source file using a command like:
| No Format |
|---|
As before, much of the metadata in the manifest file above is for human consumption. We specify which class implements the Bundle-Activator interface and also specify that our bundle exports a shared package using the Export-Package attribute. This attribute makes it possible for other bundles to import our dictionary service interface. To compile our source code, we need to have the osgi.jar file (found in Oscar's lib directory) in our class path. We compile the source file using a command like: javac -d c:\classes *.java |
This
...
command
...
compiles
...
all
...
source
...
files
...
and
...
outputs
...
the
...
generated
...
classes
...
into
...
a
...
subdirectory
...
of
...
the
...
c:\classes
...
directory;
...
this
...
subdirectory
...
is
...
tutorial\example2,
...
named
...
after
...
the
...
package
...
we
...
specified
...
in
...
the
...
source
...
file.
...
For
...
the
...
above
...
command
...
to
...
work,
...
the
...
c:\classes
...
directory
...
must
...
exist.
...
After
...
compiling,
...
we
...
need
...
to
...
create
...
a
...
JAR
...
file
...
containing
...
the
...
generated
...
package
...
directories.
...
We
...
will
...
also
...
add
...
our
...
manifest
...
file
...
that
...
contains
...
the
...
bundle's
...
meta-data to the JAR file.
...
To
...
create
...
the
...
JAR
...
file,
...
we
...
issue
...
the
...
command:
| No Format |
|---|
jar cfm example2.jar manifest.mf -C c:\classes tutorial\example2 |
This
...
command
...
creates
...
a
...
JAR
...
file
...
using
...
the
...
manifest
...
file
...
we
...
created
...
and
...
includes
...
all
...
of
...
the
...
classes
...
in
...
the
...
tutorial\example2
...
directory
...
inside
...
of
...
the
...
c:\classes
...
directory.
...
Once
...
the
...
JAR
...
file
...
is
...
created,
...
we
...
are
...
ready
...
to
...
install
...
and
...
start
...
the
...
bundle.
...
To
...
run
...
Felix,
...
we
...
follow
...
the
...
instructions
...
described
...
in
...
usage.html.
...
When
...
we
...
start
...
Felix,
...
it
...
asks
...
for
...
a
...
profile
...
name,
...
we
...
will
...
put
...
all
...
of
...
our
...
bundles
...
in
...
a
...
profile
...
named
...
tutorial.
...
After
...
running
...
Felix,
...
we
...
should
...
make
...
sure
...
that
...
the
...
bundle
...
from
...
Example
...
1
...
is
...
active.
...
We
...
can
...
use the Felix lb shell command to get a list of all bundles, their state, and their bundle identifier number. If the Example 1 bundle is not active, we should start the bundle using the start command and the bundle's identifier number that is displayed by the lb command. Now we can install and start our dictionary service bundle. Assuming that we created our bundle in the directory c:\tutorial, we can install and start it in Felix' shell using the following command:
| No Format |
|---|
the ps Oscar shell command to get a list of all bundles, their state, and their bundle identifier number. If the Example 1 bundle is not active, we should start the bundle using the start command and the bundle's identifier number that is displayed by the ps command. Now we can install and start our dictionary service bundle. Assuming that we created our bundle in the directory c:\tutorial, we can install and start it in Oscar's shell using the following command: start file:/c:/tutorial/example2.jar |
The
...
above
...
command
...
installs
...
and
...
starts
...
the
...
bundle
...
in
...
a
...
single
...
step;
...
it
...
is
...
also
...
possible
...
to
...
install
...
and
...
start
...
the
...
bundle
...
in
...
two
...
steps
...
by
...
using
...
the
...
Felix install
...
and
...
start
...
shell
...
commands.
...
To
...
stop
...
the
...
bundle,
...
use
...
the
...
Felix stop
...
shell
...
command.
...
If
...
the
...
bundle
...
from
...
Example
...
1
...
is
...
still
...
active,
...
then
...
we
...
should
...
see
...
it
...
...
out
...
the
...
details
...
of
...
the
...
service
...
event
...
it
...
receives
...
when
...
our
...
new
...
bundle
...
registers
...
its
...
dictionary
...
service.
...
Using
...
the
...
Felix shell lb command to get the bundle identifier number for our dictionary service bundle and we can stop and restart it at will using the stop and start commands, respectively. Each time we start and stop our dictionary service bundle, we should see the details of the associated service event printed from the bundle from Example 1. In Example 3, we will create a client for our dictionary service. To exit Felix, we use the shutdown command.