[Andromda-devel] AndroMDA/JIRA Commented: (SPRING-131) Allow the creation of stateful services

[Cyril C. (JIRA) <ji...@an...>]

     [ http://jira.andromda.org/browse/SPRING-131?page=comments#action_12280 ]
     
Cyril Combe commented on SPRING-131:
------------------------------------

Here is a possible strategy for implementing stateful services with Spring only. Feel free to comment as I am not an experienced Spring user.

Let's say that we have a stateful service <my.package.MyStatefulService>. The applicationContext entry for this service should look like this:

    <!-- MyStatefulService Service Proxy with inner MyStatefulService Service Implementation -->
    <bean id="myStatefulService" class="org.springframework.aop.framework.ProxyFactoryBean" singleton="false">
        <property name="target">
            <bean class="my.package.MyStatefulServiceImpl" singleton="false">
                <property name="myDao"><ref bean="myDao"/></property>
            </bean>
        </property>
        <property name="proxyInterfaces">
            <value>my.package.MyStatefulService</value>
        </property>
        <property name="interceptorNames">
            <list>
                <value>serviceTransactionInterceptor</value>
                <value>hibernateInterceptor</value>
            </list>
        </property>
    </bean>

I think that no change are required in the ServiceLocator class, but as we have set the singleton flag to <false> for both the ProxyFactoryBean and his target, it should return a new instance for each call.

Now the service should be cached on the client side. For instance, if dealing with the BPM4Struts cartridge for the web layer, a dependency from a controller to this service should produce this method in the base controller:

    /**
     * Returns a reference to the myStatefulService back-end service.
     */
    protected final my.package.MyStatefulService getMyStatefulService(HttpServletRequest request)
        throws java.lang.Exception
    {
    		javax.servlet.http.HttpSession session = request.getSession();

        my.package.MyStatefulService service = (my.package.MyStatefulService)session.getAttribute("myStatefulService");
        if (service == null)
        {
       	    service = my.package.ServiceLocator.instance().getMyStatefulService();
       	    session.setAttribute("myStatefulService", service);
       	}
        return service;
    }

If the service is not referenced in the session, we ask for a new instance to the ServiceLocator and we put it in the HttpSession object.


> Allow the creation of stateful services
> ---------------------------------------
>
>          Key: SPRING-131
>          URL: http://jira.andromda.org/browse/SPRING-131
>      Project: Spring Cartridge
>         Type: Improvement
>     Reporter: Cyril Combe
>     Assignee: Chad Brandon

>
> If a <<Service>> stereotyped classifier has instance scoped attributes, it should be implemented as a stateful service (a stateful session bean if EJBs are enabled).