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Choosing a Communication Technology

We start by looking at the different means for communicating with Web ser 

vices and applications, and then examine some typical scenarios where using Web

services based clients make sense. From there, the chapter discusses the different

types of clients that use Web services, particularly highlighting the different

design considerations for the principal Java clients: J2EE, J2SE, and J2ME cli 

ents. Then the chapter addresses the steps for developing these client applications,

from locating a service through handling errors. It also covers the communication

APIs that client applications can employ to access a service. Included in this dis 

cussion are recommendations and guidelines to help developers choose the

optimal approach. The chapter concludes with guidelines for packaging client

applications.

5.1

Choosing a Communication Technology

Web services are only one of several ways for a client to access an application ser 

vice. For example, Java applications may access application services using

RMI/IIOP, JMS, or Web services. There are advantages and disadvantages with

each of these communication technologies, and the developer must weigh these con 

siderations when deciding on the client application design. 

Interoperability is the primary advantage for using Web services as a means of

communication. Web services give clients the ability to interoperate with almost

any type of system and application, regardless of the platform on which the

system or application runs. In addition, the client can use a variety of technologies

for this communication. Furthermore, different client types such as handheld

devices, desktop browsers, or rich GUI clients running on different platforms

and written in different languages may be able to access the same set of services.

Some applications may be designed such that their functionality is only accessible

via a Web service.

Web services use HTTP as the transport protocol, which enables clients to

operate with systems through firewalls. The service's WSDL document enables

clients and services that use very different technologies to map and convert their

respective data objects. For services and clients that are based on JAX RPC, the

JAX RPC runtime handles this mapping transparently.

Let's look at the different communication approaches that are available to a

J2EE client to access a service, including Web services, RMI/IIOP, and Java

Message Service. Clients can easily use the JAX RPC generated stub classes to

access a Web service. Although not as fast from a performance perspective as