Pattern to model a business object in Seam framework ?

Question

Hi,

I habe been studying Seam framework for a long time. Altough i do not use it at work, i like its approach. It is very interesting. But i have some doubts. After reading Seam in Action book, i think it is not possible you bind more than one parameter to a business method. Something like

@Stateless
public class BusinessObjectImpl implements BusinessObject {

    public void doSomething(SomeObject i01, SomeObject i02 and so on...) {


    }

}

Am i right ? Because of it, you have two approachs:

• @In (for injection) and @Out (for outjection)

//

 @Stateless
 public class BusinessObjectImpl implements BusinessObject {

    @In
    private SomeObject input01;

    @In
    private SomeObject input02;

    @In
    private SomeObject input03;

    @Out
    private SomeObject output01;

    @Out
    private SomeObject output02;

    @Out
    private SomeObject output03;


    public void doSomething() {
        // some code
    }

}

• You can use Seam Context

//

@Stateless
public class BusinessObjectImpl implements BusinessObject {

    public void doSomething() {

        SomeObject input = Context.get("contextualName");

        SomeObject output  ...            

        Context.set("contextualName", output);
    }

}

If the first approach is used in a Stateless where it has many methods, so i think it is better you model your business object by using Command pattern. Am i right ? Something like

public class DoSomething implements Command {

    @In
    private SomeObject input01;

    @In
    private SomeObject input02;

    @Out
    private SomeObject output01;

    public void execute() {

    }

}

And you: what pattern (and good practices) do you use to avoid many member fields in a Stateless business object ?

regards,

Answer 1

No. That's completely wrong. Of course you can have many parameters in Seam methods. It's just Java. This code is fine:

@Stateless
public class BusinessObjectImpl implements BusinessObject {

    public void doSomething(SomeObject i01, SomeObject i02) {


    }
}

Of course one thing that Seam allows you do to is to inject any other Classes that you may find useful. Maybe like this:

@Stateless
public class BusinessObjectImpl implements BusinessObject {

    @In
    private AnotherObject anotherObject;

    public void doSomething(SomeObject i01, SomeObject i02) {
       anotherObject.someMethod(i01, i02);    
    }

}

EDIT (based on comment):

There are ways of passing multiple parameters from a page using JBoss EL (which allows for objects as parameters). For example

<h:form>
  <h:commandButton action="#{firstBean.performAction(secondBean, thirdBean)}">Go</h:commandButton>
</h:form>

Where your SecondBean and ThirdBean are already populated in your Session/Conversation (with their relevant @Name) and your FirstBean would look something like:

@Name("firstBean")
@Stateless
public class FirstBean {
  public void performAction(SecondBean secondBean, ThirdBean thirdBean) {
    //stuff
  }
}

But this approach isn't exactly elegant as it relies on SecondBean and ThirdBean being in your current Session/Conversation. You may be better off to follow an approach of having a page Controller or Backing Bean. This can be a POJO that then calls your SLSB. For example:

<h:form>
  <h:commandButton action="#{backingBean.performAction}">Go</h:commandButton>
</h:form>

And the Backing Bean:

@Name("backingBean")
@Scope(ScopeType.CONVERSATION)
public class BackingBean {
  @In
  private FirstBean firstBean;

  @In
  private SecondBean secondBean;

  @In
  private ThirdBean thirdBean;

  public void performAction() {
    firstBean.performAction(secondBean, thirdBean);
  }
}

Which starts to look a lot like your original question ;-)