Chapter 5 Client Design

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5.3.2 Locating and Accessing a Service

Locating a service differs depending on the client. Client applications that run in

J2EE environments use the JNDI 

InitialContext.lookup

 method to locate a ser 

vice, whereas a J2SE client can use the 

javax.xml.rpc.ServiceFactory

 class or an

implementation specific stub to locate a service. Clients use the

javax.xml.rpc.Service

 interface API to access a Web service. A stub implements

the service interface.

Code Example 5.1 shows how an application in a J2EE environment might

use a stub to access a service. The application locates the service using a JNDI

InitialContext.lookup

 call. The JNDI call returns an 

OpcOrderTrackingService

object, which is a stub. 

Context ic = new InitialContext();

OpcOrderTrackingService opcOrderTrackingSvc =

(OpcOrderTrackingService) ic.lookup(

"java:comp/env/service/OpcOrderTrackingService");

OrderTrackingIntf port = 

opcOrderTrackingSvc.getOrderTrackingIntfPort();

OrderDetails od = port.getOrderDetails(orderId); 

Code Example 5.1

Accessing a Service with a Stub in a J2EE Environment

Because it depends on the generated stub classes, the client code in Code

Example 5.1 is not the recommended strategy for using stubs. Although this

example works without problems, JAX RPC gives you a neutral way to access a

service and obtain the same results. By using the JAX RPC

javax.xml.rpc.Service

 interface method 

getPort

, you can access a Web service

in the same manner regardless of whether you use stubs or dynamic proxies. The

getPort

 method returns either an instance of a generated stub implementation

class or a dynamic proxy, and the client can then uses this returned instance to

invoke operations on the service endpoint. 

The 

getPort

 method removes the dependencies on generated service specific

implementation classes. When this method is invoked, the JAX RPC runtime

selects a port and protocol binding for communicating with the port, then config 

ures the returned stub that represents the service endpoint interface. Furthermore,

since the J2EE platform allows the deployment descriptor to specify multiple