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Designing a Service's Interaction Layer

a service unnecessarily complicated and, in these cases, it may be simpler to 

design the service as one layer. Typically, this happens in scenarios where the 

logic in either layer is too small to merit a separate layer.

The weather service scenario is one such service that might benefit from

merging the interaction and processing layers into a single layer. This type of

service does not need to preprocess incoming requests. A client request to the

service for weather information simply includes a name or zip code to identify the

location. The service looks up the location's weather information, forms a

response containing the information, and returns it to the client. Since incoming

requests require no preprocessing, a layered view of the weather service only

complicates what otherwise should be a simple service.

3.4

Designing a Service's Interaction Layer 

A service's interaction layer has several major responsibilities, and chief among

them is the design of the interface the service presents to the client. Since clients

access the service through it, the interface is the starting point of a client's interac 

tion with the service. The interaction layer also handles other responsibilities, such

as receiving client requests, delegating requests to appropriate business logic, and

creating and sending responses. This section examines the responsibilities of the

interaction layer and highlights some guidelines for its design.

3.4.1 Designing the Interface

There are some considerations to keep in mind as you design the interface of your

Web service, such as issues regarding overloading methods, choosing the endpoint

type, and so forth. Before examining these issues, decide on the approach you want

to take for developing the service's interface definition.

Two approaches to developing the interface definition for a Web service are:

1. Java to WSDL Start with a set of Java interfaces for the Web service and 

from these create the Web Services Description Language (WSDL) description 

of the service for others to use.

2. WSDL to Java Start with a WSDL document describing the details of the 

Web service interface and use this information to build the corresponding Java 

interfaces.