OSGI Blueprint Conditional Reference (ServiceMix) - reference

Question

I have two beans, b1 and b2, and a boolean property myFlag. Both b1 and b2 need to be constructed as they are used in different parts of the application. The class hierarchies of b1 and b2 are as follows:
interface MyFirstInterface { ... }
class B1Class implements MyFirstInterface { ... }
interface MySecondInterface extends MyFirstInterface { ... }
class B2Class implements MySecondInterface { ... }
In my first blueprint file, I have:
<service id="b1" interface="com.company.MyFirstInterface">
<bean class="com.company.B1Class" />
</service>
<service id="b2" interface="com.company.MySecondInterface">
<bean class="com.company.B2Class" />
</service>
In my second blueprint file, I have:
<cm:property-placeholder persistent-id="com.company.settings" update-strategy="reload">
<cm:default-properties>
<cm:property name="myFlag"/>
</cm:default-properties>
</cm:property-placeholder>
<reference id="myBean" interface="com.company.MyFirstInterface">
Assume that I want:
myBean to refer to b1 if and only if myFlag is false, and
myBean to refer to b2 if and only if myFlag is true.
Is this possible given the above configuration? If so, what needs to be done to allow this to work?
Note: I would like to avoid adding additional properties. It is not a death sentence if I really need to add one; I need a solution to this problem regardless of convenience. myFlag just happens to be an existing property in a production system so if I can get away with sticking with this one property (which is directly related to which bean should be picked), that would preferred.

Answer 1

In case anyone else encounters this, let me post the solution we came up with.
Create your two beans
<bean id="b1" class="com.company.B1Class" />
<bean id="b2" class="com.company.B2Class" />
Create a factory class
public class MyFactoryClass {
private boolean myFlag;
private B1Class b1;
private B2Class b2;
public MyFactoryClass(boolean myFlag, B1Class b1, B2Class b2) {
this.myFlag = myFlag;
this.b1 = b1;
this.b2 = b2;
}
public MyFirstInterface buildIt() {
return myFlag ? b2 : b1;
}
}
Define the factory class as a bean and use it to select the class
<bean id="myFactory" class="com.company.MyFactoryClass">
<argument value="${myFlag}"/>
<argument ref="b1"/>
<argument ref="b2"/>
</bean>
<bean id="myBean" factory-ref="myFactory" factory-method="buildIt" />
<service id="myBean" interface="com.company.MyFirstInterface" />
The full blueprints
First Blueprint:
<cm:property-placeholder persistent-id="com.company.settings" update-strategy="reload">
<cm:default-properties>
<cm:property name="myFlag"/>
</cm:default-properties>
</cm:property-placeholder>
<bean id="b1" class="com.company.B1Class" />
<bean id="b2" class="com.company.B2Class" />
<bean id="myFactory" class="com.company.MyFactoryClass">
<argument value="${myFlag}"/>
<argument ref="b1"/>
<argument ref="b2"/>
</bean>
<bean id="myBean" factory-ref="myFactory" factory-method="buildIt" />
<service id="myBean" interface="com.company.MyFirstInterface" />
Second Blueprint:
<reference id="myBean" interface="com.company.MyFirstInterface" />