Question

In Java i have abstract class named Operation and three its subclasses called OperationActivation, OperationPayment and OperationSendEmail.

ADDED FROM COMMENT: Operation* objects are EJB Entity Beans so I can’t have business logic inside them.

No I want to create processor class like this:

public class ProcessOperationService {

public void processOperation(Operation operation) {
    out.println("process Operation");
    process(operation);
}

public void process(OperationActivation operationActivation) {
    out.println("process Activation");
}

public void process(OperationPayment operationPayment) {
    out.println("process Payment");
}

public void process(OperationSendEmail operationSendEmail) {
    out.println("process OperationSendEmail");
}        

}

Processing each operation requires different logic so I want to have three different methods , one for each operation.

Of course this code doesn’t compile. Am I missing something or it can’t be done that way?

Answer 1

Shouldn’t your Operation* objects be doing the work themselves ? So you can write (say)

for (Operation op : ops) {
   op.process();
}

You can encapsulate the logic for each particular operation in its own class, and that way everything related to OperationPayment remains in the OperationPayment class. You don’t need a Processor class (and so you don’t need to modify a Processor class everytime you add an Operation)

There are more complex patterns to enable objects to mediate wrt. what they need to execute, but I’m not sure you need something that complex at this stage.