THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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The iPOJO Snack Bar
This tutorial illustrates some advanced features of iPOJO
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Context
This tutorial is based on a very simple application; customers are using a vendor service to buy hot dog or pop corn according to the availability of appropriate providers. Both of the vendors implement (and provide) the vendor service. The hot dog vendor depends on two others services to get the ingredients (buns and wiener). To sell pop corn, the pop corn vendor requires having enough corn in stock.
Preparing the tutorial
The tutorial archive is available here. This archive contains both the source code and a pre-configured version of Felix. First, unzip the archive. Then, launch ant to compile the bundles composing this tutorial. Once compiled, you can launch Felix and start the tutorial. To launch, Felix launch the following command from the felix directory:
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{html} h1. The iPOJO Snack Bar _This tutorial illustrates some advanced features of iPOJO_ {div:class=toc} {toc:maxLevel=4|minLevel=2} {div} h2. Context This tutorial is based on a very simple application; customers are using a vendor service to buy hot dog or pop corn according to the availability of appropriate providers. Both of the vendors implement (and provide) the vendor service. The hot dog vendor depends on two others services to get the ingredients (buns and wiener). To sell pop corn, the pop corn vendor requires having enough corn in stock. !vendor.png! h2. Preparing the tutorial The tutorial archive is available [here|http://people.apache.org/~clement/ipojo/tutorials/advanced/advanced.tutorial.zip]. This archive contains both the source code and a pre-configured version of Felix. First, unzip the archive. Then, launch _'ant'_ to compile the bundles composing this tutorial. Once compiled, you can launch Felix and start the tutorial. To launch, Felix launch the following command from the {{felix}} directory: {code} java -jar bin/felix.jar {code} h2. Writing a component providing two services The sources of this project are inside the _ |
Writing a component providing two services
The sources of this project are inside the vendor.buns-and-wieners
...
directory.
...
The
...
hot
...
dog
...
vendor
...
requires
...
at
...
the
...
same
...
time
...
the
...
bun
...
service
...
and
...
the
...
wiener
...
service.
...
In
...
our
...
application
...
these
...
services
...
are
...
provided
...
by
...
the
...
same
...
component.
...
This
...
component
...
can
...
be
...
implemented
...
as
...
follows
...
(src\org\apache\felix\ipojo\example\vendor\provider\BunWienerProvider.java):
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{code:java} public class BunWienerProvider implements BunService, WienerService { public void getBun() { System.out.println("Get a bun"); } public void getWiener() { System.out.println("Get a wiener"); } } {code} |
This
...
class
...
just
...
implements
...
the
...
two
...
service
...
interfaces.
...
Its
...
descriptor
...
(contained
...
in
...
the
...
metadata.xml
...
file)
...
is:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:xml} <ipojo> <component classname="org.apache.felix.ipojo.example.vendor.provider.BunWienerProvider" name="buns_and_wieners" public="false"> <provides/> </component> <instance component="buns_and_wieners"/> </ipojo> {code} |
In
...
the
...
descriptor,
...
we
...
declare
...
a
...
component
...
type
...
for
...
this
...
vendor
...
which
...
contains
...
the
...
implementation
...
class.
...
The
...
"classname"
...
attribute
...
contains
...
the
...
qualified
...
name
...
of
...
the
...
component
...
implementation.
...
The
...
"name"
...
attribute
...
is
...
the
...
component
...
type
...
name.
...
It
...
is
...
only
...
used
...
to
...
refer
...
to
...
this
...
type.
...
The
...
"public=false"
...
attribute
...
disables
...
factory
...
exposition.
...
A
...
component
...
type
...
publishing
...
a
...
factory
...
provides
...
a
...
way
...
to
...
create
...
instance
...
of
...
this
...
type
...
from
...
outside
...
this
...
descriptor.
...
In
...
our
...
case,
...
we
...
want
...
to
...
guarantee
...
that
...
only
...
one
...
instance
...
(singleton)
...
can
...
be
...
created,
...
so
...
we
...
disable
...
the
...
factory
...
mechanism.
...
iPOJO
...
manages
...
service
...
publication
...
and
...
providing
...
automatically
...
at
...
runtime.
...
The
...
"<provides/>"
...
element
...
means
...
that
...
the
...
component
...
provides
...
services.
...
If
...
this
...
element
...
is
...
not
...
present,
...
iPOJO
...
will
...
publish
...
all
...
implemented
...
interfaces
...
by
...
the
...
implementation
...
class
...
(and
...
parent
...
class
...
too).
...
In
...
our
...
case,
...
it
...
will
...
publish
...
the
...
BunService
...
and
...
WienerService
...
interfaces.
...
Finally,
...
we
...
create
...
one
...
instance
...
of
...
our
...
component.
...
The
...
instance
...
contains
...
the
...
component
...
attribute
...
describing
...
the
...
component
...
type
...
to
...
use.
...
We
...
use
...
the
...
component
...
type
...
name
...
to
...
target
...
the
...
wanted
...
component
...
type.
...
At
...
runtime,
...
the
...
bundle
...
containing
...
this
...
component
...
will
...
create
...
an
...
instance
...
which
...
provides
...
the
...
BunService
...
and
...
the
...
WienerService.
...
Publishing service properties
The sources of this project are inside the vendor.hotdog directory.
The hot dog vendor only provides the Vendor service. To provide this service, it uses a bun service and a wiener service. The following code (contained in the src/org/apache/felix/ipojo/example/vendor/hotdog/HotDogVendor.java
...
file)
...
shows
...
a
...
very
...
simple
...
implementation
...
of
...
this
...
component:
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{code:java} public class HotDogVendor implements Vendor { /** * Bun provider (required service). */ private Bun bunProvider; /** * Wiener provider (required service). */ private Wiener wienerProvider; /** * Sell method. * To provide an hotdog, the vendor consume a bun and a wiener. * This method is synchronized to avoid serving to client * at the same time. * @return a hotdog. * @see org.apache.felix.ipojo.example.vendor.service.Vendor#sell() */ public synchronized Product sell() { bunProvider.getBun(); wienerProvider.getWiener(); return new HotDog(); } {code} |
Once
...
implemented,
...
we
...
need
...
to
...
describe
...
this
...
component
...
type.
...
The
...
descriptor
...
file
...
is
...
the
...
metadata.xml
...
file.
...
The
...
field
...
attributes
...
in
...
the
...
"requires"
...
elements
...
are
...
used
...
to
...
inject
...
the
...
required
...
services.
...
At
...
runtime,
...
iPOJO
...
injects
...
automatically
...
a
...
BunService
...
provider
...
in
...
the
...
"bunProvider"
...
field
...
and
...
a
...
WienerService
...
provider
...
in
...
the
...
"wienerProvider"
...
field.
...
The
...
implementation
...
uses
...
these
...
fields
...
the
...
same
...
way
...
it
...
would
...
have
...
used
...
any
...
other
...
fields
...
(as
...
illustrated
...
in
...
the
...
sell
...
method).
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:xml} <ipojo> <component classname="org.apache.felix.ipojo.example.vendor.hotdog.HotDogVendor" name="HD" public="false"> <provides/> <requires field="bunProvider"/> <requires field="wienerProvider"/> </component> <instance component="HD"/> </ipojo> {code} |
The
...
component
...
type
...
declares
...
a
...
provided
...
service
...
(the
...
Vendor
...
Service).
...
Then,
...
the
...
component
...
declares
...
the
...
two
...
service
...
dependencies
...
(using
...
the
...
"requires"
...
element).
...
However,
...
we
...
would
...
like
...
to
...
add
...
a
...
service
...
property
...
on
...
the
...
Vendor
...
service
...
describing
...
the
...
sold
...
product
...
(here,
...
"hotdog").
...
To
...
achieve
...
this,
...
we
...
just
...
need
...
to
...
add
...
a
...
property
...
element
...
in
...
the
...
"provides"
...
tags:
| Code Block | ||||
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| ||||
{code:xml} <ipojo> <component classname="org.apache.felix.ipojo.example.vendor.hotdog.HotDogVendor" name="HD" public="false"> <provides> <property name="product" type="string" value="hotdog"/> </provides> <requires field="bunProvider"/> <requires field="wienerProvider"/> </component> <instance component="HD"/> </ipojo> {code} |
iPOJO
...
then
...
publishes
...
the
...
"product"
...
property
...
in
...
the
...
"vendor"
...
service
...
registration.
...
This
...
property
...
has
...
the
...
"hotdog"
...
value.
...
Publishing
...
'dynamic'
...
properties
...
The
...
bun
...
service
...
and
...
the
...
wiener
...
service
...
can
...
also
...
expose
...
service
...
properties.
...
In
...
our
...
case,
...
these
...
service
...
properties
...
will
...
describe
...
the
...
stock
...
of
...
ingredients.
...
Each
...
time
...
the
...
service
...
is
...
used,
...
the
...
property
...
value
...
is
...
decreased.
...
To
...
achieve
...
this,
...
we
...
modify
...
the
...
current
...
implementation
...
to
...
add
...
a
...
field
...
representing
...
the
...
property:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:java} public class BunWienerProvider implements BunService, WienerService { private int bunStock; private int wienerStock; public synchronized void getBun() { bunStock = bunStock - 1; } public synchronized void getWiener() { wienerStock = wienerStock - 1; } } {code} |
The
...
stock
...
accesses
...
are
...
synchronized
...
to
...
avoid
...
multiple
...
accesses
...
at
...
the
...
same
...
time.
...
The
...
component
...
type
...
metadata
...
must
...
also
...
be
...
modified
...
in
...
order
...
to
...
describe
...
this
...
property:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:xml} <ipojo> <component classname="org.apache.felix.ipojo.example.vendor.provider.BunProvider" name="buns_and_wieners" public="false"> <provides> <property name="buns" field="bunStock" value="10"/> <property name="wieners" field="wienerStock" value="10"/> </provides> </component> <instance component="buns_and_wieners"/> </ipojo> {code} |
In
...
the
...
"provides"
...
element,
...
two
...
properties
...
are
...
added.
...
This
...
property
...
contains
...
a
...
"field"
...
attribute
...
aiming
...
to
...
attach
...
the
...
service
...
property
...
with
...
a
...
field
...
of
...
the
...
implementation
...
class.
...
Then
...
a
...
default
...
value
...
is
...
given.
...
In
...
the
...
code,
...
the
...
property
...
fields
...
will
...
obtain
...
the
...
initial
...
value
...
(10).
...
Then
...
each
...
time
...
the
...
fields
...
are
...
modified,
...
the
...
service
...
property
...
is
...
updated
...
(as
...
well
...
as
...
the
...
OSGi™
...
service
...
registration).
...
Notice
...
that
...
iPOJO
...
support
...
method
...
injection
...
for
...
property
...
too.
...
In
...
this
...
case,
...
a
...
getter
...
method
...
is
...
called
...
to
...
inject
...
the
...
property
...
value.
...
Configuring
...
instances
...
In
...
the
...
previous
...
example,
...
the
...
properties
...
were
...
configured
...
in
...
the
...
component
...
type
...
description.
...
It
...
is
...
also
...
possible
...
to
...
customize
...
any
...
property
...
value
...
in
...
the
...
instance
...
declaration.
...
This
...
way,
...
each
...
instance
...
can
...
obtain
...
different
...
values.
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:xml} <ipojo> <component classname="org.apache.felix.ipojo.example.vendor.provider.BunProvider" name="buns_and_wieners" public="false"> <provides> <property name="buns" field="bunStock" value="10"/> <property name="wieners" field="wienerStock" value="10"/> </provides> </component> <instance component="buns_and_wieners"> <property name="buns" value="9"/> <property name="wieners" value="8"/> </instance> </ipojo> {code} |
The
...
previous
...
metadata
...
shows
...
how
...
to
...
push
...
a
...
configuration
...
in
...
instance
...
declarations.
...
The
...
instance
...
declaration
...
contains
...
two
...
property
...
elements
...
containing
...
the
...
name
...
of
...
the
...
value
...
of
...
the
...
property.
...
Instance
...
configuration
...
override
...
component
...
type
...
initial
...
value.
...
Properties
...
are
...
optional
...
by
...
default
...
;
...
that's
...
means
...
that
...
they
...
do
...
not
...
need
...
to
...
receive
...
a
...
value.
...
In
...
this
...
case,
...
default
...
values
...
are
...
the
...
same
...
as
...
the
...
Java
...
default
...
fields
...
values
...
(boolean
...
:
...
false,
...
int
...
:
...
0,
...
double
...
:
...
0.0d,
...
...).
...
You
...
can
...
specify
...
that
...
a
...
property
...
must
...
receive
...
a
...
default
...
value
...
from
...
either
...
the
...
component
...
type
...
description
...
or
...
the
...
instance
...
configuration
...
by
...
setting
...
the
...
mandatory
...
attribute
...
to
...
'true'.
Using filter in service requirements
Now that bun and wiener providers publish their remaining stock, the hot dog provider can look for a bun service and a wiener service with a non empty stock. To achieve this, we must describe an LDAP filter in the service requirement description. The following XML snipped shows this metadata:
| Code Block | ||||
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h2. Using filter in service requirements Now that bun and wiener providers publish their remaining stock, the hot dog provider can look for a bun service and a wiener service with a non empty stock. To achieve this, we must describe an LDAP filter in the service requirement description. The following XML snipped shows this metadata: {code:xml} <ipojo> <component classname="org.apache.felix.ipojo.example.vendor.hotdog.HotDogVendor" name="HD" public="false"> <provides> <property name="product" type="string" value="hotdog"/> </provides> <requires field="bunProvider" filter="(buns>=1)"/> <requires field="wienerProvider" filter="(wieners>=1)"/> </component> <instance component="HD"/> </ipojo> {code} |
When
...
a
...
provider
...
does
...
no
...
more
...
matches
...
with
...
the
...
LDAP
...
filter,
...
the
...
provider
...
is
...
no
...
more
...
used,
...
and
...
another
...
(matching
...
with
...
the
...
filter)
...
is
...
tracked.
...
If
...
no
...
provider
...
fulfilling
...
the
...
constraint
...
is
...
found,
...
the
...
instance
...
becomes
...
invalid
...
and
...
waits
...
a
...
matching
...
provider.
...
| HTML |
|---|
...
<div class="box">
<div class="box-blue-header">
<div class="box-blue-title">
<img src="http://people.apache.org/~clement/ipojo/site/information.gif"> <b>Instance invalidation and services</b>
</div>
</div>
<div class="box-blue-content">
When an instance becomes invalid, all its provided services are withdrawn from the service registry. So, this instance is no more _accessible_ from the service registry.
</div>
<div class="box-blue-footer"></div>
</div>
|
Immediate component instance
Now that we get the hot dog provider, we are going to implement customers. Customers are implemented in the vendor.customer project). A customer simply looks for a vendor service and buys a product:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{html} h2. Immediate component instance Now that we get the hot dog provider, we are going to implement customers. Customers are implemented in the _vendor.customer_ project). A customer simply looks for a vendor service and buys a product: {code:java} public class Customer { private VendorService vendor; private String name; public Customer() { System.out.println("Customer " + name + " bought " + vendor.sell() + " from " + vendor.getName()); } {code} |
The
...
previous
...
code
...
shows
...
a
...
possible
...
implementation
...
of
...
a
...
customer.
...
However,
...
the
...
"sell"
...
method
...
is
...
called
...
in
...
a
...
constructor,
...
and
...
the
...
constructor
...
can
...
only
...
be
...
called
...
only
...
if
...
an
...
object
...
of
...
the
...
class
...
is
...
created.
...
With
...
iPOJO
...
there
...
are
...
two
...
different
...
way
...
to
...
"activate"
...
an
...
instance
...
as
...
soon
...
as
...
it
...
becomes
...
valid.
...
The
...
first
...
one
...
uses
...
the
...
lifecycle
...
callback
...
(described
...
in
...
the
...
previous
...
tutorial).
...
The
...
second
...
one
...
is
...
by
...
declaring
...
the
...
component
...
as
...
an
...
immediate
...
component.
...
An
...
immediate
...
component
...
instance
...
creates
...
an
...
object
...
of
...
its
...
implementation
...
as
...
soon
...
as
...
it
...
becomes
...
valid.
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:xml} <ipojo> <component classname="org.apache.felix.ipojo.example.vendor.customer.Customer" name="customer" immediate="true"> <requires field="vendor"/> <properties> <property field="name"/> </properties> </component> </ipojo> {code} |
To
...
declare
...
a
...
component
...
immediate,
...
just
...
add
...
"immediate=true"
...
in
...
the
...
component
...
descriptor.
...
Then
...
as
...
soon
...
as
...
the
...
vendor
...
service
...
is
...
available,
...
the
...
object
...
is
...
created.
...
Moreover,
...
this
...
type
...
declares
...
a
...
property
...
(to
...
give
...
a
...
name
...
to
...
the
...
customers).
...
This
...
property
...
is
...
not
...
a
...
service
...
property,
...
but
...
just
...
an
...
internal
...
property.
...
As
...
for
...
service
...
properties,
...
the
...
name
...
field
...
will
...
be
...
injected
...
by
...
a
...
value
...
necessary
...
given
...
during
...
the
...
instance
...
creation
...
(i.e.
...
contained
...
inside
...
the
...
instance
...
configuration).
...
By
...
default,
...
all
...
all
...
components
...
that
...
do
...
not
...
provide
...
any
...
service
...
are
...
immediate.
...
Other
...
components
...
create
...
call
...
their
...
constructors
...
when
...
they
...
are
...
used
...
for
...
the
...
first
...
time.
...
| HTML |
|---|
<div class="box">
<div class="box-blue-header">
<div class="box-blue-title">
<img src="http://people.apache.org/~clement/ipojo/site/information.gif"> <b>Difference between 'validate' and 'immediate'</b>
</div>
</div>
<div class="box-blue-content">
There is a difference between immediate components and components with a 'validate' lifecycle callback. Indeed, the callback is call at each time the instance becomes valid and calls the constructor only if no object already exists. On the other side, the immediate component's constructor is call only once.
</div>
<div class="box-blue-footer"></div>
</div>
|
...
Creating instances from an external component type
In the previous section we have declared a customer component type, which does not have the "public=false"
...
attribute.
...
This
...
feature
...
allows
...
separate
...
deployment
...
from
...
instance
...
creation.
...
Moreover,
...
we
...
didn't
...
declare
...
instances
...
in
...
the
...
descriptor.
...
Another
...
metadata
...
file
...
can
...
be
...
used
...
to
...
declare
...
instances
...
from
...
the
...
customer
...
type,
...
this
...
descriptor
...
being
...
contained
...
in
...
another
...
bundle.
...
The
...
following
...
descriptor
...
creates
...
10
...
customer
...
instances
...
(look
...
at
...
the
...
vendor.customer.creator\metadata.xml
...
file):
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:xml} <ipojo> <instance component="customer"> <property name="name" value="customer-1"/> </instance> <instance component="customer"> <property name="name" value="customer-2"/> </instance> <instance component="customer"> <property name="name" value="customer-3"/> </instance> <instance component="customer"> <property name="name" value="customer-4"/> </instance> <instance component="customer"> <property name="name" value="customer-5"/> </instance> <instance component="customer"> <property name="name" value="customer-6"/> </instance> <instance component="customer"> <property name="name" value="customer-7"/> </instance> <instance component="customer"> <property name="name" value="customer-8"/> </instance> <instance component="customer"> <property name="name" value="customer-9"/> </instance> <instance component="customer"> <property name="name" value="customer-10"/> </instance> </ipojo> {code} |
Once
...
deployed,
...
this
...
bundle
...
looks
...
for
...
the
...
required
...
factory.
...
If
...
it's
...
not
...
available
...
the
...
bundle
...
waits
...
for
...
the
...
factory.
...
As
...
soon
...
as
...
the
...
required
...
factory
...
is
...
available,
...
all
...
instances
...
are
...
created.
...
When
...
this
...
bundle
...
is
...
stopped,
...
all
...
instances
...
are
...
destroyed.
...
Deploying
...
the
...
application
...
Compile
...
the
...
bundles,
...
by
...
launching
...
ant
...
at
...
the
...
root
...
of
...
the
...
tutorial.
...
Then
...
launch
...
Felix
...
is
...
indicated
...
above.
...
Once
...
started,
...
launch
...
the
...
following
...
commands
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:shell} start file:../vendor.services/output/vendor.services.jar start file:../vendor.buns-and-wieners/output/vendor.buns-and-wieners.jar start file:../vendor.hotdog/output/vendor.hotdog.jar start file:../vendor.customer/output/vendor.customer.jar start file:../vendor.customer.creator/output/vendor.customer.creator.jar {code} |
Something
...
like
...
this
...
should
...
appear:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:shell} Customer customer-1 bought Hotdog from Fenway Park Customer customer-2 bought Hotdog from Fenway Park Customer customer-3 bought Hotdog from Fenway Park Customer customer-4 bought Hotdog from Fenway Park Customer customer-5 bought Hotdog from Fenway Park Customer customer-6 bought Hotdog from Fenway Park Customer customer-7 bought Hotdog from Fenway Park Customer customer-8 bought Hotdog from Fenway Park {code} |
Only
...
8
...
customers
...
can
...
buy
...
a
...
hot-dog,
...
as
...
the
...
stock
...
of
...
wieners
...
and
...
buns
...
can't
...
supply
...
more
...
hot-dog.
...
The
...
remainder
...
of
...
this
...
tutorial
...
will
...
try
...
to
...
solve
...
the
...
problem
...
of
...
these
...
two
...
hungry
...
customers.
...
Using
...
the
...
lifecycle
...
controller
...
Sometimes
...
you
...
want
...
to
...
invalidate
...
your
...
instance
...
in
...
the
...
code
...
(for
...
example:
...
to
...
unregister
...
a
...
service).
...
That's
...
possible
...
with
...
the
...
lifecycle
...
controller
...
handler.
...
Let's
...
take
...
the
...
popcorn
...
vendor
...
with
...
a
...
corn
...
stock
...
from
...
the
...
vendor.popcorn
...
project.
...
Each
...
time
...
it
...
sells
...
some
...
popcorn,
...
its
...
stock
...
is
...
decreased.
...
When
...
the
...
stock
...
reaches
...
0,
...
it
...
cannot
...
sell
...
popcorns
...
any
...
more
...
(so
...
the
...
vendor
...
service
...
needs
...
to
...
be
...
withdrawn).
...
The
...
following
...
implementation
...
(
...
src\org\apache\felix\ipojo\example\vendor\popcorn\PopCornVendor.java
...
)
...
uses
...
a
...
field
...
to
...
control
...
the
...
lifecycle.
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:java} /** * The corn stock. */ private int m_corn_stock; /** * Lifecycle controller. * If set to false, the instance becomes invalid. */ private boolean m_can_sell = true; /** * The sell method. * To provide popcorn, the vendor needs to decrease its corn stock level. * This method is synchronized to avoid to client being serve at * the same time. * @return * @see org.apache.felix.ipojo.example.vendor.service.Vendor#sell() */ public synchronized Product sell() { m_corn_stock--; if (m_corn_stock == 0 && m_can_sell) { // Last pop corn m_can_sell = false; System.out.println("Stop selling popcorn ... Run out of stock"); return new PopCorn(); } else if (m_corn_stock > 0) { // Normal case return new PopCorn(); } else { // Cannot serve. return PopCorn.NO_MORE_POPCORN; } } {code} |
Once
...
the
...
field
...
is
...
set
...
to
...
"false",
...
the
...
instance
...
is
...
invalidated
...
(the
...
vendor
...
service
...
is
...
no
...
more
...
available).
...
To
...
configure
...
the
...
controller,
...
you
...
can
...
use
...
the
...
following
...
metadata:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:xml} <ipojo> <component classname="org.apache.felix.ipojo.example.vendor.popcorn.PopCornVendor" name="popcorn" public="false" architecture="true"> <provides/> <controller field="m_can_sell"/> </component> <instance component="popcorn"/> </ipojo> {code} |
The
...
instance
...
can
...
be
...
re-validated
...
by
...
setting
...
the
...
field
...
to
...
true.
...
So,
...
no
...
deploy
...
the
...
pop
...
corn
...
vendor.
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:shell} -> start file:../vendor.popcorn/output/vendor.popcorn.jar Customer customer-10 bought popcorn from D & P Customer customer-9 bought popcorn from D & P {code} |
Our
...
two
...
last
...
customers
...
are
...
no
...
more
...
hungry.
...
However,
...
new
...
customers
...
arrives,
...
we
...
have
...
the
...
following
...
situation:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:shell} -> update 10 Customer customer-1 bought popcorn from D & P Customer customer-2 bought popcorn from D & P Stop selling popcorn ... Run out of stock Customer customer-3 bought popcorn from D & P {code} |
To
...
recreate
...
new
...
customers,
...
just
...
update
...
the
...
customer.creator
...
bundle
...
(bundle
...
10).
...
So,
...
now
...
we
...
have
...
7
...
customers
...
hungry!
...
There
...
is
...
neither
...
popcorn
...
nor
...
hotdog!
...
Reconfiguring
...
an
...
instance
...
OSGi
...
specified
...
the
...
Configuration
...
Admin
...
mechanism
...
aiming
...
to
...
handler
...
service
...
and
...
bundle
...
configuration.
...
This
...
section
...
will
...
describe
...
how
...
you
...
can
...
use
...
the
...
Configuration
...
Admin
...
and
...
iPOJO
...
to
...
add
...
corn
...
inside
...
our
...
popcorn
...
vendor.
...
First,
...
we
...
will
...
change
...
the
...
pop
...
corn
...
vendor
...
to
...
add
...
a
...
method
...
reinjecting
...
the
...
new
...
stock:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:java} /** * A transporter refills the stock of corn. * This method is synchronized to avoid to client being served * during the update. * @param newStock : the stock of corn to add to the current stock. */ public synchronized void refillStock(int newStock) { m_corn_stock += newStock; System.out.println("Refill the stock : " + m_corn_stock); if (m_corn_stock > 0) { m_can_sell = true; } } {code} |
Once
...
added,
...
we
...
need
...
to
...
update
...
the
...
component
...
type
...
descriptor
...
to
...
use
...
this
...
method:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:xml} <ipojo> <component classname="org.apache.felix.ipojo.example.vendor.popcorn.PopCornVendor" name="popcorn" architecture="true"> <provides/> <controller field="m_can_sell"/> <properties> <property name="stock" method="refillStock" value="5"/> </properties> </component> <instance component="popcorn" name="SuperPopCorn"> <property name="managed.service.pid" value="Super.PopCorn.Stock"/> </instance> </ipojo> {code} |
We
...
add
...
two
...
different
...
things.
...
First
...
we
...
add
...
a
...
"stock"
...
property
...
attached
...
to
...
the
...
refillStock
...
method.
...
When
...
this
...
instance
...
is
...
configured
...
or
...
reconfigured,
...
this
...
method
...
is
...
called
...
to
...
push
...
the
...
new
...
stock
...
value.
...
Then
...
we
...
add
...
the
...
managed.service.pid
...
property
...
inside
...
the
...
instance
...
creation.
...
This
...
property
...
will
...
be
...
used
...
by
...
the
...
Configuration
...
Admin
...
to
...
attach
...
configuration
...
to
...
instances.
...
The
...
property
...
value
...
must
...
be
...
unique.
...
So
...
now,
...
our
...
popcorn
...
vendor
...
can
...
be
...
reconfigured
...
dynamically
...
to
...
get
...
increments
...
its
...
corn
...
stock.
...
However,
...
we
...
need
...
to
...
create
...
something
...
refilling
...
the
...
stock
...
...
...
a
...
corn
...
transporter
...
!
...
Inside
...
the
...
vendor.corn.transporter
...
project,
...
we
...
have
...
a
...
component
...
dealing
...
with
...
the
...
ConfigurationAdmin
...
to
...
push
...
the
...
new
...
pop
...
corn
...
vendor
...
configuration.
...
The
...
implementation
...
is
...
contained
...
in
...
the
...
src\org\apache\felix\ipojo\example\vendor\corn\transporter\CornTransporter.java
...
file.
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:java} public class CornTransporter { private ConfigurationAdmin m_configAdmin; /** * Reconfigure the popcorn vendor with the configuration admin. */ public void refillStock() { try { // Retrieve or Create the instance configuration // from the configuration admin Configuration configuration = m_configAdmin.getConfiguration("Super.PopCorn.Stock", "file:../vendor.popcorn/output/vendor.popcorn.jar"); configuration.setBundleLocation( "file:../vendor.popcorn/output/vendor.popcorn.jar"); Properties props = new Properties(); props.put("stock", new Integer(15)); // Delivered corn configuration.update(props); System.out.println("Update the configuration of " + configuration.getPid() + "(" + configuration.getBundleLocation() + ")"); configuration.delete(); } catch (IOException e) { e.printStackTrace(); } } } {code} |
Create
...
a
...
new
...
configuration
...
from
...
the
...
configuration
...
admin
...
and
...
configure
...
this
...
configuration
...
to
...
add
...
corn.
...
Then,
...
we
...
update
...
this
...
configuration.
...
This
...
will
...
reconfigured
...
our
...
popcorn
...
vendor.
...
More
...
information
...
on
...
the
...
Configuration
...
Admin
...
is
...
available
...
in
...
the
...
OSGi
...
R4
...
Compendium.
...
So,
...
now
...
if
...
we
...
deploy
...
this
...
bundle,
...
we
...
will
...
provide
...
enough
...
corn
...
to
...
feed
...
all
...
the
...
customers:
| Code Block | ||||
|---|---|---|---|---|
| ||||
{code:shell} -> start file:../vendor.corn.transporter/output/vendor.corn.transporter.jar Update configuration of Super.PopCorn.Stock( file:../vendor.popcorn/output/vendor.popcorn.jar) Refill the stock : 5 Customer customer-10 bought popcorn from D & P Customer customer-9 bought popcorn from D & P Customer customer-8 bought popcorn from D & P Customer customer-7 bought popcorn from D & P Customer customer-6 bought popcorn from D & P Customer customer-5 bought popcorn from D & P Customer customer-4 bought popcorn from D & P {code} |
That's
...
it!
...
Conclusion
This small tutorial has presented some of of the iPOJO features. Subscribe to the Felix users mailing list by sending a message to users-subscribe@felix.apache.org
...
;
...
after
...
subscribing,
...
...
questions
...
or
...
feedback
...
to
...
...
.
| Include Page | ||||
|---|---|---|---|---|
|
...