Java Reference
In-Depth Information
Table 12.2
Blueprint manager value objects
(continued)
Manager
Value
<reference>
A proxy object to the service registered in the OSGi service registry.
<reference-list>
A
java.util.List
containing proxies to the registered services or
ServiceReferences
.
This capability makes it possible to define reasonably sophisticated constructions in
the component
XML
descriptions. Consider a contrived example in the following
XML
snippet:
<bean class="com.acme.FooImpl">
<property name="services">
<map>
<entry key="bar">
<service interface="com.acme.Bar">
<bean class="com.acme.BarImpl"/>
</service>
</entry>
</map>
</property>
</bean>
In this example, you construct a
Foo
object into which you inject its
services
property
with a
Map
. For the map, you set the
bar
key to the
ServiceRegistration
object for a
service
Bar
. The
Bar
service is provided by an inlined bean, constructed from the
BarImpl
class. The
FooImpl
class looks something like this:
public class FooImpl {
public void setServices(Map<String, ServiceRegistration> services) {
for (Map.Entry<String, ServiceRegistration> e : services.getEntrySet())
{
String key = e.getKey();
ServiceRegistration val = e.getValue();
System.out.println("Registered service " + key + "=" + val);
}
}
}
Here, the
FooImpl
class is injected with a property whose value is wholly constructed
from the Blueprint
XML
model. This is definitely a contrived example, but it shows
the flexibility of the Blueprint model.
SCOPES
As with manager values, Blueprint has inherited the concept of scope from Spring
Dynamic Modules. A scope can be applied to bean and service managers; it defines
the lifetime over which the specified manager is applicable. Blueprint defines two
scopes—
singleton
and
prototype
—but they imply subtly different behavior depending
on whether they're applied to a bean or a service manager, as shown in table 12.3.
