Required and provided interfaces on Component Diagrams

[Diego Marques]

Hi everyone,

I have passed on the first part of the SCEA and now I am going to start the second part.

But before, I want to clarify a doubt which I always had.

What exactly is a required and a provided interface on a component diagram?

I have always read the following:

A provided interface is like a connector where another components can connect to use some behaviors of the component who provides this interface.

A required interface is like a connector where another component needs to connect to provide some behavior to this component.

I don't know if I really got the meaning.

Let's say, for example, in an EJB 3.0 environment. A SessionBean called "MySessionBean" implements a local interface called "MySessionLocal".

And let's say that there is a Servlet called "MyServlet", which uses the MySessionBean through the "MySessionLocal" interface.

In this scenario, if I say:

The "MySessionBean" is a component that has a provided interface called "MySessionLocal";

The "MyServlet" is a component that has a required interface called "MySessionLocal".

Are these statements right?

Or, in case not, could someone give me an example using EJB's, for example?

Thanks a lot!

[Ryan Fernandes]

this is how I look at it:

If you session bean exposes a functionality to manage bank accounts and ...
your servlet is a component that requires the above functionality to fulfill its contract with its client...

In this scenario, you can then say:
# The "MySessionBean" is a component that has a 'provided interface' called "manageBankAccount";
# The "MyServlet" is a component that has a 'required interface' called "manageBankAccount".

Note: dont confuse "java interface" with "functionality interface"

[Diego Marques]

So, all my servlets that require a reference to an EJB, have a required interface for those EJB's?

And all these EJB's have a provided interface?

Is it right?

[Ryan Fernandes]

So, all my servlets that require a reference to an EJB a provider , have a 'required interface' for those EJB's that functionality

whether that functionality is provided by your EJB or a POJO or a Web service is secondary.

[Diego Marques]

Ryan Fernandes wrote:

So, all my servlets that require a reference to an EJB a provider , have a 'required interface' for those EJB's that functionality

whether that functionality is provided by your EJB or a POJO or a Web service is secondary.

Hi Ryan,

What do you mean by "is secondary"?

Thanks

[Ryan Fernandes]

what I meant is when you depict your servlet on the component diagram, you might draw it with a 'required interface' (half bubble).
You can then draw a dependency arrow (from the above half bubble) to any component's 'provided interface' (full bubble). That component could be anything (pojo, web service, ejb etc).
I hope I've clarified this for you.

Good luck with your assignment.