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11.6 Service Requester
Oracle Application Server makes creating a Web Services requester, or client
program, extremely easy. As mentioned earlier, OC4J Web Services
provide a Web Services home page for each deployed Web Service as
shown in Figure 11-5. On this home page are links to
a WSDL file, and Web Services proxy files generated by the Web
Services Assembler program. The Web Services Assembler tool can even
generate a Web Service proxy for Web Services not published on Oracle
Application Server. In addition to supporting service calls, a proxy
generated by the Web Services Assembler also supports SOAP headers.Oracle Application Server defines two types of clients that can
execute a Web Service: a static client and a dynamic client. These
clients are described in the next sections.
11.6.1 Static Client
A static client , in
Oracle's terminology, is one that is created with
all the information necessary to execute a Web Service. To access an
OC4J Web Service as a static client, all you need is to create a Java
program that makes a copy of the proxy object for the service and
then use the proxy to call a method by the same name and with the
same parameters as the service.
11.6.2 Dynamic Client
A dynamic client
is one
that looks up an available Web Service and executes it at runtime. In
this case, the client doesn't know the location of
the Web Service or may not even know the name of the Web Service
until the time that it looks up available Web Services in a UDDI
directory. Once it locates a service (either because
it's the first service found or because it uses some
other type of determination to choose one of multiple services), the
dynamic client looks up its specification via a link to a WSDL file
and then uses the specifications in the WSDL file to invoke the
desired Web Service.Oracle Application Server provides two Java packages,
oracle.j2ee.ws.client
and
oracle.j2ee.ws.client.wsdl, that work in concert
to dynamically invoke a Web Service given the location of a
WSDL file. If you combine these with
the use of the UDDI API, you can indeed dynamically identify and
execute a Web Service at runtime.
11.6.3 Web Services Security
Oracle Application
Server supports
authentication and authorization for
Web Services using the same mechanisms as for other Oracle
Application Server applications. Authentication is enabled using
JAAS as implemented in OC4J.
Web Services can ensure data privacy and integrity by using
Chapter 4 describes overall Oracle Application
Server security.
