Database Reference
In-Depth Information
SQL can do a lot). It will be quite right to say that PL/SQL nowadays can be seen as a
wrapper for Java, thanks to SQLJ specification. You can create your own Servlet, compile
it, and load it into your DB using the following:
loadjava -grant public -user <xdbuser>/xdbuserpwd>@<XDBSID>
CustomServlet.class
Then, register it in /xdbconfig.xml in a preceding section where we discussed the
configuration of Oracle XML DB.
However, native DB Java capabilities are wider than just XDB functionality. You can do
practically everything—from transaction control and complex XML operations to file
handling—putting aside the UTL_FILE package. Again, despite being perfectly feasible,
this solution should be clearly analyzed for scalability requirements.
From messaging infrastructure in addition to synchronous HTTP(S) calls, Oracle DB can
offer the native support of reliable asynchronous communications compatible with JMS
queuing, known as Advanced Queuing ( AQ ). AQ is a database-integrated messaging in-
frastructure. Thus, all the DBs' operational benefits, such as High Availability, Scalability,
and Reliability, are applicable to the messages and queues in AQ. Standard database fea-
tures such as backup and recovery and security and manageability are available for AQ as
well. All AQ features can be accessed from the DB side by Java or PL/SQL (the two main
packages are DBMS_AQADM and DBMS_AQ ), where you can enqueue, dequeue (one or a
group of messages), sort, propagate, and perform many other functions. The payload data
type could be opaque (ANYDATA) or based on a predefined abstract data type (ADT).
Messaging interfaces on the consumer side can be based on any popular programming in-
terface, but naturally, in Fusion Middleware, the Java JMS API is used (the or-
acle.jms package).
All the previously discussed features present Oracle DB (we are talking about the classic
RDBMS 11 g ) as a perfect platform candidate for DB-related Entity services and some
utility, such as the File Gateway SOA pattern, responsible for fetching files, and trans-
forming and persisting in single or multiconsumer AQ(s). However, the role of DB as a
process state deferral store for task-orchestrated services is hard to underestimate. It's a
primary feature of Oracle RDBMS in Fusion Middleware, employed in Framework 4.
DB-based Rule centralization, Policy centralization, and storage for runtime-related XML
artifact (XSLTs, XPaths, other XML fragments, and XQuery as well), together with reli-
able messaging persistence in AQ, cover all the types of runtime data persistence we need.
Responsible for design-time, Discoverability Services metadata is also securely kept in an
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