5

C H A P T E R

Client Design

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EB

 services take the Web client model to the next level. Developers can write

far more powerful clients whose interaction with Web services provides a rich client

experience. In this environment, client developers need not have control over the

server portion of an application, yet they can still write powerful, rich client applica 

tions. This chapter focuses on using the Java platform to design and develop Web

services based clients.

Clients can take advantage of Web services to obtain a wide range of func 

tions or services. To a client, a Web service is a black box: The client does not

have to know how the service is implemented or even who provides it. The client

primarily cares about the functionality the service provided by the Web ser 

vice. Examples of Web services include order tracking services, information look 

up services, and credit card validation services. Various clients running on differ 

ent types of platforms can all access these Web services.

One of the principal reasons for implementing Web services is to achieve

interoperability. Clients can access Web services regardless of the platform or

operating system upon which the service is implemented. Not only is the service's

platform of no concern to the client, the client's implementation language is com 

pletely independent of the service. 

Web service clients can take many forms, from full blown J2EE applications,

to rich client applications, even to light weight application clients, such as wire 

less devices. In short, there are many different types of clients that can talk to Web

services. The Java platform provides excellent support for writing Web service

clients. Web services also provide clients a standardized approach to access ser 

vices through firewalls. Such access extends the capabilities of clients. Clients

accessing Web services also remain more loosely coupled to the service.

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