Java Web Services: Up and Running, 2nd Edition

The RandService in Two Files

The RandService in the first example (see Example 4-1) combines, in a single source file, what JAX-WS calls the SEI (Service Endpoint Interface) and the SIB (Service Implementation Bean). The SEI specifies, at a high level that befits an interface, the service operations, and the SIB provides an implementation of the operations. A SIB can be one of the following:

• A POJO class such as RandService annotated as @WebService and encapsulating service operations, each annotated as a @WebMethod.
• A @Stateless Session EJB that is likewise annotated as a @WebService. EJBs in general predate JAX-WS; hence, this second type of SIB is an inviting way to expose legacy EJBs as web services.

Chapter 7 covers the EJB implementation of a @WebService. For now, the SIBs will be POJO classes. For convenience, most of my examples take the single-file approach, which combines the SEI and the SIB into one class annotated as a @WebService. The two-file approach is illustrated with the SEI RandService (see Example 4-4) in one file and the SIB RandImpl (see Example 4-5) in another file. The RandService is now an interface, whereas the RandImpl is a class that implements this interface.

Example 4-4. The Service Endpoint Interface for the revised RandService

package rand2;

import javax.jws.WebService;
import javax.jws.WebMethod;
import java.util.Random;

@WebService
public interface RandService {
    @WebMethod
    public int next1();
    @WebMethod
    public int[ ] nextN(final int n);
}

Example 4-5. The Service Implementation Bean for the revised RandService

package rand2;

import javax.jws.WebService;
import javax.jws.WebMethod;
import java.util.Random;

@WebService(endpointInterface = "rand2.RandService")
public class RandImpl implements RandService {
    private static final int maxRands = 16;

    @WebMethod
    public int next1() { return new Random().nextInt(); }
    @WebMethod
    public int[ ] nextN(final int n) {
        final int k = (n > maxRands) ? maxRands : Math.abs(n);
        int[ ] rands = new int[k];
        Random r = new Random();
        for (int i = 0; i < k; i++) rands[i] = r.nextInt();
        return rands;
    }
}

In the SIB class RandImpl, the @WebService interface has an attribute, the key/value pair:

endpointInterface = "rand2.RandService"

that names the SEI. It is still important for the class RandImpl to employ the standard implements clause because only the implements clause prompts the compiler to make sure that the public methods declared in the SEI, in this case the two methods annotated with @WebMethod, are defined appropriately in the SIB.

The revised RandService has the same functionality as the original. The Endpoint publisher changes slightly:

Endpoint.publish(url, new RandImpl()); // SIB, not SEI

The second argument to the publish changes to RandImpl precisely because, in the revision, RandService is an interface. In general, the second argument to the static version of publish is always the SIB. In a single-file case such as the original version of RandService, a single class is the combined SEI and SIB.