86

Designing a Service's Interaction Layer

E

It is not advisable to put in a handler business logic or processing particular to 

specific requests and responses.

You cannot store client specific state in a handler: A handler's logic acts on

all requests and responses that pass through an endpoint. However, you may use

the handler to store port specific state, which is state common to all method calls

on that service interface. Note also that handlers execute in the context of the

component in which they are present.

E

Do not store client specific state in a handler.

Also note that handlers work directly on the SOAP message, and this involves

XML processing. You can use handlers to pass client specific state through the

message context. (See  Passing Context Information on Web Service Calls  on

page 366.)

E

Use of handlers can result in a significant performance impact for the service 

as a whole.

Use of handlers could potentially affect the interoperability of your service.

See the next section on interoperability. Keep in mind that it takes advanced

knowledge of SOAP message manipulation APIs (such as SAAJ) to correctly use

handlers. To avoid errors, Web service developers should try to use existing or

vendor supplied handlers. Using handlers makes sense primarily for writing

system services such as auditing, logging, and so forth.

3.4.1.7

Interoperability

A major benefit of Web services is interoperability between heterogeneous plat 

forms. To get the maximum benefit, you want to design your Web service to be

interoperable with clients on any platform, and, as discussed in Chapter 2, the Web

Services Interoperability (WS I) organization helps in this regard. WS I promotes a

set of generic protocols for the interoperable exchange of messages between Web

services. The WS I Basic Profile promotes interoperability by defining and recom 

mending how a set of core Web services specifications and standards (including

SOAP, WSDL, UDDI, and XML) can be used for developing interoperable Web

services.