Database Reference
In-Depth Information
Thus, we have standard configurable Servlet features to listen and receive any data (in-
cluding XML) into Oracle XML DB. But what about the HTTP posting? This functional-
ity is extremely well-covered by the
UTL_* PL/SQL
packages,
UTL_HTTP
in particu-
lar. With this package, you can manage the following:
• Session settings
• HTTP requests/responses
• HTTP cookies handling
• HTTP persistent connections
• HTTP error conditions
We will cover this functionality in detail when discussing the SOA-oriented DB APIs.
While sending and receiving the XML data, we must be able to handle the payload inside
the DB: store, register, transform, validate, and map to the relational structures. The key
element here is
XMLType
, the abstract Oracle type capable of representing the XML data.
Moreover,
XMLIndex
can sort XML data in addition to the B-tree and Oracle text in-
dexes. XDB provides a complete range of XML-related functions for this data type to
handle XML itself (add, modify, and delete nodes, siblings, and elements) and register it
in DB. Oracle XML DB Repository provides a hierarchical way of storing XML docu-
ments, overcoming the disadvantages of a relational model. A repository provides all the
necessary file-handling features including versioning, tagging, and access control based
on the
access control lists
(
ACL
).
Despite the existing security mechanisms in XDB, we would not recommend direct access
to the XDB features for external service consumers, thus bypassing the security perimeter
and Service Gateways. There are many reasons for that as XDB simply does not provide
the necessary security-related patterns, discussed earlier for layer 7, visualized in the first
figure of this chapter but one reason has to be mentioned explicitly. The implementation
of the Trusted Subsystem SOA security pattern requires the separation of security ac-
counts for the service and the service's underlying resources. Nevertheless, for internal
consumers, or for consumers isolated by means of
Secure Gateway
(
SG
) in layer 7, XDB
provides an excellent opportunity for the entity-oriented service model's implementations.
The principle of concerns' separation is maintained by the segregation of security features
delegated to the SG and the entity service's basic operations delegated to the XDB. The
main concern here should be the scalability because, for better results, we need a more
atomic service realization.
Surely, for XDB Servlet creation, complex XPath operations, transformations, and so on,
you can rely on something more robust than PL/SQL (although the oldie but goodie PL/
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