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A portal is a Web site that contains a variety of content that can either be
configured by a user or by a domain administrator. Portals pages generally
contain multiple small windows of information that can be updated
autonomously from the rest of the page.
Web services are a natural fit for a portal site because content can be
retrieved from any arbitrary site using the technologies and features that
Web services offer.
Web services, today, are typically embodied within the following four
operations:
1) Implement - Web services are currently generally developed using the
SOAP-over-HTTP protocol. This involves packaging content as an XML document
with remote procedure call (RPC) encodings or as one discreet XML document.
Either type of packaging embeds the payload contents within an entity called
a "SOAP Envelope."
2) Describe - Once a Web service has been implemented, its content and
semantics need to be described in order to be effectively used by external
parties.
3) Publish - Web services can be published to registries, such as UDDI or
ebXML, in order to be located by interested consumers.
4) Locate - Once a Web service has been published and described, consumers
can locate the Web service and make remote calls to it to retrieve the data.
Using these four operations, a portal site can effectively find content and
publish content. Within a J2EE environment, a portal site can expose
content to client browsers as sets of related business services that are
implemented using the Java programming language.
A typical scenario might involve a user directing a Web browser to the
portal site, where a Java servlet can field the HTTP request and dispatch it
to the appropriate business service. The business service can retrieve the
desired content from a particular Web service using a variety of available
technologies including AXIS, Apache SOAP and the Java Web Services Developer Pack. Once the content has been retrieved, it can be formatted appropriately for the user's browser and returned.
AXIS, Apache SOAP and the Java Web Services Developer Pack all provide the
necessary tools for implementing a full-scale portal site within the J2EE
environment. To avoid the costs and headaches of building a portal site
entirely from scratch, I recommend that you start with a commercial platform
that does a lot of the work for you such as the Zareus Application Platform from Zareus, Inc., the WASP Server for Java from Systinet, CapeConnect from Cape Clear and others.
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