What is a stateless session bean?

A stateless session bean is an enterprise bean (EJB component) that provides a stateless service to the client. Conceptually, the business methods on a stateless session bean are similar to procedural applications or static methods; there is no instance state, so all the data needed to execute the method is provided by the method arguments.

The stateless session bean is an EJB component that implements the javax.ejb.SessionBean interface and is deployed with the declarative attribute "stateless". Stateless session beans are called "stateless" because they do not maintain conversational state specific to a client session. In other words, the instance fields in a stateless session bean do not maintain data relative to a client session. This makes stateless session beans very lightweight and fast, but also limits their behavior.

Stateless session beans are usually developed as a set of related and simple services. Think of a session bean as a functional API where each business method represents an isolated independent service. An example is a CreditService bean that provides methods for making charges against different types of credit cards (MC, Visa, Discovery, etc).

public class CreditService implements javax.ejb.SessionBean {

    public Charge charge (String accountToCredit, CreditCard card, double amount)
    throws ValidationException, RemoteException{
               
               // attempt to obtain Merchant bean representing the retailer making the charge.
               try{
                   MerchantHome mrchntHome = ... get VendorHome reference
                   Merchant merchant = mrchntHome.findByPrimaryKey(vendorToCredit);      
               }catch(ObjectNotFoundException onfe){
                         throw new ValidationException("Invalid merchant account number");
               }         

               // attempt to create a Charge bean based on the vendor, amount, and credit card info
               try{
                   ChargeHome chgHome = ... get ChargeHome reference
                   Charge charge =  chgHome.create(merchant, card, amount);
                    return charge;
              }catch(CreateException ce){
                        throw new ValidationException(ce.getMessage());
              }
   }
...
}