How are @In(create = true) and @Name connected?

[wise_guybg]

Hi,
In the application I work on all entity beans had an @Name. I considered this unnecessary and removed it.

I tested the application and on one page an NPE occured. It was complaining that a field with @Out had a null value. This field is declared like this:

@In(required = false, create = true)
@Out
ExamData examData;

As it turns out, if the ExamData entity has @Name the "create" attribute of @In works and otherwise not. Can someone explain to me what is happening?

[limousyf]

Mmm, first @Out complains about nullity because you didn't specify that it wasn't required (required=false).
This means the outjected value must not be null

About the @Name, if I understand your question, the link is done on the var name.
If you inject ExamData examData; Seam will look for "examData" in the contexts.
If you specify that you want to look for myExamData for example, it's done like this:

@In(value="myExamData")

[wise_guybg]

Yes, @Out needs a not-null value and this is why I added create=true.

My question is why does the creation depend on whether I have @Name or not.

BTW Is there a case in which problems arise from having @Name("examData") and a field @In @Out ExamData examData?

[pmuir]

@Name registers your class as a Seam component. If you don't put @Name on it and @In it, then you need to provide another way of instantiating e.g. a factory.

[wise_guybg]

Thanks for the explanation. It has helped me turn my attention on the In annotation. Here is what the javadoc states:

 /**
 * Specifies that a component should be instantiated
 * if the context variable is null.
 */
 boolean create() default false;

and have a look at Component.java

private static Object getInstance(String name, boolean create, Object result)

where it is said that:

 if (result==null && create)
 {
 result = getInstanceFromFactory(name);
 if (result==null)
 {
 if (component==null)
 {
 //needed when this method is called by JSF
 if ( log.isDebugEnabled() ) log.debug("seam component not found: " + name);
 }

And here it is:

2007-08-23 13:26:51,459 DEBUG [org.jboss.seam.Component] seam component not found: examData

I understand it better now.