[jboss-jira] [JBoss JIRA] Created: (JBSEAM-368) STATELESS component injection rules are not intuitive/undocumented

[Christian Bauer (JIRA)]

STATELESS component injection rules are not intuitive/undocumented
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                 Key: JBSEAM-368
                 URL: http://jira.jboss.com/jira/browse/JBSEAM-368
             Project: JBoss Seam
          Issue Type: Bug
            Reporter: Christian Bauer
            Priority: Minor


This is probably a non-issue, so feel free to ignore.

It took me a while to figure out why this works:

@In(create=true)
MyStatelessComponent myComponent;

but this doesn't:
@In
MyStatelessComponent myComponent;

It was easy to figure out that it apparently is required, but from looking at the documentation this isn't clear. I also found it difficult to think about "creation of a component" when it is already there in the stateless EJB pool. I checked the code and there is some consistency in the internal logic, of course.

Users however might read the docs and say: "@In searches all contexts hierarchically, so it should find myComponent in STATELESS, because Seam logged that binding on startup." 

Also, attempts to remove the create="true" with 

@In(value = "myComponent", scope = ScopeType.STATELESS)
MyStatelessComponent myComponent;

resulted in JNDI lookup("myComponent"), which makes not much sense and returns null.

I suggest we add something to the documentation about lookup/injection of stateless components (I'm not sure if I'm 100% right about this, otherwise I would have added it).

Side note, I found the following additional debug logging lines in Component.java very helpful during development:

   private Object getInstanceToInject(In in, String name, Object bean, boolean enforceRequired)
   {
      Object result;
      if ( name.startsWith("#") )
      {
         log.debug("Searching for injection variable with value binding expression: " + name);
         FacesContext facesCtx = FacesContext.getCurrentInstance();
         Application application = facesCtx.getApplication();
         result = application.createValueBinding(name).getValue(facesCtx);
      }
      else if (in.scope()==ScopeType.UNSPECIFIED)
      {
         log.debug("Searching hierarchically for injection variable in all scopes: " + name);
         result = getInstance(name, in.create());
      }
      else
      {
         if ( in.create() )
         {
            throw new IllegalArgumentException(
                  "cannot combine create=true with explicit scope on @In: " +
                  getAttributeMessage(name)
               );
         }
         log.debug("Searching for injection variable in scope: " + name + ", scope: " + in.scope());
         result = in.scope().getContext().get(name);
      }

      if (result==null && enforceRequired && in.required())
      {
         throw new RequiredException(
               "In attribute requires value for component: " +
               getAttributeMessage(name)
            );
      }
      else
      {
         return result;
      }
   }


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