Struts 2 , TypeConversion, Spring Injection

[Eric Nielsen]

I've run across something slightly confusing to me in getting Dependency Injection with Spring to work with Type Converters under Struts 2.

I tried creating a StrutsTypeConverter subclass that had a @Transactional annotation with a @PersistenceContext on an EntityManager field. The Converter was declared as a bean in the applicationContext. However the EM was not injected.

I then made a wrapper class (Workspace) around an EntityManager (only exposes a get/set EntityManager), this wrapper class also had the @Transaction and @PersistenceContext annotations. The Workspace was declared in the application context.

I then made the converter expose a setWorkspace method. The converter was no longer listed in the ApplicationContext. However now the EM gets successfully injected into the Workspace; and the Workspace gets injected into the converter.

What is the difference, in these two approaches that causes one to work and one to not?

Is there something unique about the StrutsTypeConverter class that causes auto-wire by name works successfully (without even a bean definition of the converter), but not @Transactional/@PersistenceContext annotations?

[Eric Nielsen]

So I got an answer to this on the struts users' mailing list. Here's the gist of it, in case anyone was wondering what was going on.

The Struts 2 ObjectFactory (normally backed by the Spring plugin, but other options are available) is responsible for creating all Actions, Converters, and Interceptors used by the framework. The default configuration of the struts-spring plugin will do a Spring autowire-by-name from the application context on the created objects. It does not, however have the functionality provided by PersistenceAnnotationBeanPostProcessor. Thus you can't use @PersistenceContexts annotations to inject EntityManagers into Actions, Converters, or Interceptors.