How to use a seam component in an other one?

[mikool]

Hi guys!

I know that this a newbie question but I just can't make it work after reading and trying all day.
I want to use a simple component in an other one.
First I have this class:

@Stateless
@Name("ProcessManager")
@Startup
@Scope(ScopeType.APPLICATION)
public class ProcessManager implements ProcessManagerInterface{
     
          public void dosth(){
               System.out.println("=====Hello World=====");
                }
}

Then I have this interface:

public interface ProcessManagerInterface {  
    
     public void dosth();     
     
}

Finally I have this test class:

@Name("testing")
public class Test {
     
     @In(required=false)
     ProcessManagerInterface processManager;
     
     public void dosth() {
          processManager.dosth();
     }

}

So, I restarted my server I tried to execute {testing.dosth()} but I always get a null pointer exception.
Please, tell me how can I use my ProcessManager Component in an other component?

Thanks in advance.
Mike

[mail.micke]

Hi

Seam looks up objects to inject via the name of the property, processManager in you case.

Since you named it ProcessManager it won't find it.

To fix that use

@In("#{ProcessManager}")

You might want to add a

create=true 

to the injection as well so it is created if doesn't
already exist.

Cheers,
micke

[mikool]

Thanks, it works so far.
But I cannot add

create=true

Can you give me an example how to use

@In("#{ProcessManager}")

and add

create=true

?
Thanks.

[mikool]

I also would like to know if it is possible to solve this problem without using EL in the annotation @In?

[mail.micke]

Seems like you don't have to use EL, looks like just using context variable name should work documentation.

Example:

@Name("testing")
public class Test {
     
     @In(value="ProcessManager", required=false)
     // or I wouldn't use @In(value="#{ProcessManager}", required=false)
     // or @In(value="ProcessManager", create=true)
     ProcessManagerInterface processManager;
     
     public void dosth() {
          processManager.dosth();
     }

}

[mikool]

If I use

@In(value="ProcessManager", required=false)

without EL then I get an NullPointerException.

[gjeudy]

It is a mistake to try to give a Seam scope to a stateless session bean. Seam does not manage the lifecycle of the stateless session bean. Moreover I don't think the @Startup annotation works on an EJB for the same reason. Check the seam sourcecode you will see @Startup is only used on POJOs which makes sense.

I would try removing @Stateless from your example.

@Name("ProcessManager")
@Startup
@Scope(ScopeType.APPLICATION)
public class ProcessManager implements ProcessManagerInterface{
     
          public void dosth(){
               System.out.println("=====Hello World=====");
                }
}

public interface ProcessManagerInterface {  
    
     public void dosth();     
     
}

@Name("testing")
public class Test {
     
     @In(value="ProcessManager")
     ProcessManagerInterface processManager;
     
     public void dosth() {
          processManager.dosth();
     }

}

You could rename your

@Name("processManager")

and then just:

@In
processManager

should work.

If you require a @Stateless EJB then remove @Startup and @Scope and just use:

@In(value="ProcessManager", create=true)

[mikool]

Thanks!
Now it works very well!
But when I don't use

@In(create=true)

I get a null Pointer Exception.