Java Reference
In-Depth Information
The final lifecycle-related issue we'll discuss is how Blueprint components gain
access to the underlying
OSG
i execution environment.
ENVIRONMENT MANAGER
As you've seen so far, the Blueprint specification uses managers to control various
aspects (such as services, references, and beans) of a component. Each manager
defines and controls the specific lifecycle characteristics of its associated aspect. The
same pattern is applied to entities outside of the component; these are called
environ-
ment managers
. In this case, environment managers are effectively property-value mac-
ros. They come in four types:
■
blueprintContainer
—Provides access to the Blueprint container object and
allows various forms of component introspection
■
blueprintBundle
—Provides access to the Blueprint bundle's
Bundle
object
■
blueprintBundleContext
—Provides access to the Blueprint bundle's
Bundle-
Context
object
■
blueprintConverter
—Provides access to an object implementing the
Con-
verter
interface, which we'll discuss shortly
Let's look at how you use the
blueprintBundleContext
manager in the paint applica-
tion to access the
BundleContext
. The
WindowListener
needs the bundle context so it
can retrieve the system bundle to shut down the
OSG
i framework when the paint
frame is closed. In the following snippet's
WindowListener
component
XML
descrip-
tion, you use the environment manager to inject the bundle context into the
Window-
Listener
class as a property:
<bean id="listener" class="org.foo.windowlistener.WindowListener">
<property name="bundleContext" ref="blueprintBundleContext" />
</bean>
This follows the same pattern as the reference-injection mechanism of accessing ser-
vice references. The implementation code in the
WindowListener
class looks like this:
private BundleContext m_context;
...
public void setBundleContext(BundleContext context) {
m_context = context;
}
The bundle context ends up being injected using an ordinary setter method.
With this, we'll conclude the discussion of the Blueprint version of the paint pro-
gram. To see it in action, go to the chapter12/paint-example-bp/ directory of the topic's
companion code. Type
ant
to build the example and
java
-jar
launcher.jar
bundles/
to run it. This example uses the Apache Aries (
http://incubator.apache.org/aries/
)
implementation of the Blueprint specification.
In the final section on Blueprint, we'll look at some other advanced features it
provides.
