On Wed, Feb 18, 2009 at 04:45:26PM +0000, Christian Helmbold wrote:
> I've read http://cwiki.apache.org/WICKET/spring.html and the corresponding
> section in "Wicket in Action" about the troubles with serialization of
> injected services.
>
> "Dependencies often have references to other dependencies in the
> container, and so if one is serialized it will probably serialize a few
> others and can possibly cascade to serializing the entire container."
> (http://cwiki.apache.org/WICKET/spring.html)
>
> As
> far as I understand this is not a dependency injection specific issue.
> In either case all referenced objects are serialized recursively. So I
> think I have to take care about serialization not only when using
> Spring or Guice.
>
> Wouldn't it be sufficient to use a static member to hold a reference to a
> service? i.e.
>
> public class SomeWicketComponent{
> private static MyService service;
> // ...
> }
>
How would you intialize these? Would you have a static getter, and force
yourself to remember to always use it? Or would you have a static setter
and centralize the initialization code somewhere else? Either way sounds
ugly to me.
> Remains
> the problem with the injection. To solve this the mentioned website
> suggests several ways. The Application Object Approach seems to be most
> wicket like to me. But as mentioned there it is very verbose. Why not
> simply insert a method to deliver requested beans into the Application
> class? It would look like this:
>
> class MyApplication extends WebApplication {
> private ApplicationContext ctx = new ClassPathXmlContext("context.xml");
> // Spring context
> public Object getBean(String beanName){
> return ctx.getBean(beanName);
> }
> }
>
> Is
> anything wrong with it?
The problem is you'll end up with code like this sprinkled throughout
your app:
MyService svc = (MyService) MyApp.getBean("myService");
Let's see, where to start...
- it's ugly
- the cast and the bean name can fail in a way that is only detectable
at runtime
- it ties all your components to your application class
- it's difficult to test, since you need to mock up a MyApp instance for
your component to work
> I find it much more elegant than to store a
> reference for each bean in in the application class as suggested on
> http://cwiki.apache.org/WICKET/spring.html#Spring-ApplicationObjectApproach.
>
I don't find either very elegant.
> Maybe the annotation-based approach is a bit more elegant but I don't like
> annotations much.
>
What don't you like about them? Annotations are a tool just like any
other part of the language. A carpenter doesn't use a brick because he
"doesn't like hammers much."
> It
> seems to me, that dependency injection (DI) and wicket is not a dream
> team. Do you use DI with Wicket or do you use the "classic" approach
> like Wicket itself does?
>
I've been very happy with @SpringBean so far.
jk
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