How to "white label" spring beans

Question

We have a white labeled application (one application supporting a branded experience for multiple customers). We would like to be able to load a co-brand version of a component to support custom components per customer. For example something like:

<!-- default service -->
<bean id="service" class="com.blah.myService" primary="true">
  <property name="myBean" ref="bean" />
</bean>
<!-- custom service for client 123 -->
<bean id="service_123" class="com.blah.myService">
  <property name="myBean" ref="bean" />
</bean>

<!-- default bean -->
<bean id="bean" class="com.blah.Bean" primary="true"/>
<!-- bean for client 123 -->
<bean id="bean_123" class="com.blah.Bean" />

We have tried subclassing the ApplicationContext, and this works for the top-level bean, but the autowired collaborators are wired and cached during the loading of spring.

As an example, if I invoke getBean("service"), I can intercept the call in my custom ApplicationContext and return service_123, but the "bean" property uses the cached version and does not invoke the getBean method again, thus I am unable to wire in the custom version.

Is there an easy way to achieve this type of runtime custom injection?

Answer 1

First of all, you perhaps don't need to subclass ApplicationContext to implement this kind of custom instantiation logic - you can create a BeanPostProcessor instead.

To solve a problem with the cached version of a bean, you can wrap the returned bean into some kind of proxy - either using AOP or manually (for example, see TargetSource and its subclasses).

Answer 2

One way it would be manually loading these beans:

myAppContext.getBean("bean_" + customer.getId());

If you need your class to access an instance of the ApplicationContext, make your class implement ApplicationContextAware.