Overview

The Fulcrum Spring Framework Service allows embedding a Spring container as Avalon service or the other way round, i.e. embedding YAAFI and Avalon services in a Spring container.

The main goal of the implementation was providing transparent service lookup and embedding across the two different containers.

  • embedding Spring into YAAFI
  • embedding YAAFI into Spring
  • lookup Spring beans from within Avalon services
  • inject Avalon services into Spring beans
If you would like to have a closer look at the functionality and features please check the regression tests.

Embedding Spring into YAAFI

In this scenario the Spring container is created within the SpringFrameworkService implementation. Within the Spring container the Avalon services are exposed using a Spring FactoryBean and the exposed Avalon services can be used for dependency injection. 
          
<!-- Get a hold on an Avalon Service Manager -->
<bean id="avalonContainerBean"
  class="org.apache.fulcrum.yaafi.service.servicemanager.ServiceManagerServiceImpl"
  factory-method="getInstance"
/>

<!-- Expose an Avalon service using a Spring factory bean -->
<bean id="systemPropertyService"
  class="org.apache.fulcrum.spring.AvalonServiceFactoryBean">
    <property name="serviceManager" ref="avalonContainerBean"/>
    <property name="serviceName" value="systemPropertyService"/>
</bean>

<!-- Create a Spring bean and inject the Avalon service -->
<bean id="customSpringService" class="org.apache.fulcrum.spring.CustomSpringServiceImpl">
    <property name="greeting" value="Hello Avalon!!!"/>
    <property name="serviceManager" ref="avalonContainerBean"/>
    <property name="systemPropertyService" ref="systemPropertyService"/>
</bean>
Please note that Avalon services can use Spring beans as well relying on the standard service lookup mechanism. 
          
public void service(ServiceManager serviceManager) 
  throws ServiceException
{
    this.customSpringService = (CustomSpringService) 
      serviceManager.lookup("customSpringService");
}

Technically this is implemented by telling YAAFI about components managing their own services. This information is contained in the 'serviceManagers' section of the container configuration file. 

          
<fulcrum-yaafi>
  <serviceManagers>
    <serviceManager>springFrameworkService</serviceManager>
  </serviceManagers>
</fulcrum-yaafi>

Embedding YAAFI into Spring

In this scenario the YAAFI Avalon container is created as Spring bean and the Avalon services within YAAFI are exposed using a Spring FactoryBean. This approach is not overly elegant since it requires some boiler-plate XML code to export Avalon services but it is trivial and works for all Spring versions in the wild. 

          
<!-- Instantiate YAAFI using a container configuration file -->   
<bean id="avalonContainerBean"
  class="org.apache.fulcrum.spring.YaafiContainerBean"
  init-method="initialize"
  destroy-method="dispose">
    <property
      name="containerConfigValue"
      value="./src/test/avalonIntoSpringContainerConfiguration.xml"
    />
</bean>

<!-- Expose an Avalon service using a Spring factory bean -->
<bean id="systemPropertyService"
  class="org.apache.fulcrum.spring.AvalonServiceFactoryBean">
    <property name="serviceManager" ref="avalonContainerBean"/>
    <property name="serviceName" value="systemPropertyService"/>
</bean>

<!-- Create a Spring bean and inject the Avalon service -->
<bean id="customSpringService"
  class="org.apache.fulcrum.spring.CustomSpringServiceImpl">
    <property name="greeting" value="Hello Avalon!!!"/>
    <property name="serviceManager" ref="avalonContainerBean"/>
    <property name="systemPropertyService" ref="systemPropertyService"/>
</bean>

Please note that Avalon services can use Spring beans as well relying on the standard service lookup mechanism. Technically this is implemented by wrapping the Spring container into a class exposing a Service Manager interface and using this wrapper as parent service lookp. If the YAAFI instance in question does not find a service it delegates the service lookup to its parent Service Manager - in this case the Spring Framework - which can successfully resolve the service. 

          
public void service(ServiceManager serviceManager) 
  throws ServiceException
{
    this.customSpringService = (CustomSpringService) 
      serviceManager.lookup("customSpringService");
}

Supported Spring Framewok Releases

The service was tested with the following Spring releases
  • Spring 1.2.9
  • Spring 2.0.8
  • Spring 2.5.4

Using a different Avalon Container

This library is not directly tied to Fulcrum YAAFI apart from creating a YAAFI container for testing using the YaafiContainerBean. So if you have the code to bootstrap your favourite Avalon container you are also able from the integration effort.