76

Designing a Service's Interaction Layer

E

Considering this mapping between Java and MIME types, it is best to send im 

ages and XML documents that are in a Web service interface using the Java 

types shown in Table 3.1. However, you should be careful about the effect on 

the interoperability of your service. See  Interoperability  on page 86 for more 

details.

3.4.1.3.2 XML Documents as Parameters

There are scenarios when you want to pass XML documents as parameters. Typi 

cally, these occur in business to business interactions where there is a need to

exchange legally binding business documents, track what is exchanged, and so

forth. Exchanging XML documents as part of a Web service is addressed in a sepa 

rate section see  Handling XML Documents in a Web Service  on page 105 for

guidelines to follow when passing XML documents as parameters.

3.4.1.3.3 Handling Nonstandard Type Parameters

JAX RPC technology, in addition to providing a rich standard mapping set between

XML and Java data types, also provides an extensible type mapping framework.

Developers can use this framework to specify pluggable, custom serializers and

deserializers that support nonstandard type mappings. 

E

Extensible type mapping frameworks, which developers may use to support 

nonstandard type mappings, are not yet a standard part of the J2EE platform.

Vendors currently can provide their own solutions to this problem. It must be

emphasized that if you implement a service using some vendor's implementation 

specific type mapping framework, then your service is not guaranteed to be porta 

ble and interoperable.

E

Because of portability limitations, you should avoid passing parameters that re 

quire the use of vendor specific serializers or deserializers.

Instead, a better way is to pass these parameters as SOAP document frag 

ments represented as a DOM subtree in the service endpoint interface. (See Figure

3.3.) If so, you should consider binding (either manually or using JAXB) the

SOAP fragments to Java objects before passing them to the processing layer to

avoid tightly coupling the business logic with the document fragment.