Web service endpoint implementation class is used by the Web service client to access a stateless session bean. It is typically the primary programming artifact for enterprise bean Web service endpoints. It declares the methods that a client can invoke on the service. An interface is not required while building a JAX-WS endpoint. The Web service implementation class implicitly defines an SEI (service endpoint implementation). A Web service endpoint implementation class must conform to the following rules:
It must be annotated with either the javax.jws.WebService or javax.jws.WebServiceProvider annotations.
It may explicitly reference an SEI through the endpointInterface element of the @WebService annotation, but is not required to do so. If no endpointInterface is specified in @WebService, an SEI is implicitly defined for the implementing class.
The business methods of the class must be public, and must not be declared static or final.
Business methods that are exposed to Web service clients must be annotated with javax.jws.WebMethod.
Business methods that are exposed to Web service clients must have JAXB-compatible parameters and return types.
It must not be declared final and must not be abstract.
It must have a default public constructor.
The endpoint class must be annotated @Stateless.
It must not define the finalize method.
It may use the javax.annotation.PostConstruct or javax.annotation.PreDestroy annotations on its methods for life-cycle event callbacks.
The @PostConstruct method is called by the container before the class begins responding to Web service clients.
The @PreDestroy method is called by the container before the endpoint is removed from operation.
For example:

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The Web service endpoint interface is used to define the ‘Web services methods’. It is necessary for an enterprise bean that implements the Web service to implement methods having the same signature, as the methods of the Web service endpoint interface. There are a numbers of restrictions exist on which types to use as parameters and results of service endpoint interface methods. It provides the client’s view of the Web service, hiding the stateless session bean from the client. A Web service endpoint interface must conform to the rules of a JAX-RPC service definition interface. A Web service endpoint interface must conform to the following rules:
It should extend the java.rmi.Remote interface.
It must not have constant declarations, such as public, final, or static.
The methods must throw the java.rmi.RemoteException or one of its subclasses. Method parameters and return types must be supported JAX-RPC types.
For example:

A remote client is a location independent client of an enterprise bean. A client that runs in the same JVM as a bean instance uses the same API to access the bean as a client that runs in a different JVM on the same or different machine. The remote client uses a remote interface that specifies the remote business methods that a client can call on an enterprise bean. It also uses a remote home interface that specifies the methods used by remote clients for locating, creating, and removing instances of enterprise bean classes. The following are the characteristics of a remote client:
It is allowed to run on a different machine and a different Java virtual machine (JVM) than the enterprise bean it accesses.