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Enterprise Java

Make the Java-Oracle9i connection

Put Oracle9i's object-oriented features to work

By Terry Camerlengo and Carl Johnson, JavaWorld.com, 06/13/03

One of Java's most appealing features is platform neutrality: Java gives you the ability to port applications to numerous operating systems without tie-ins to a particular application server, IDE, or even database vendor. This flexibility is the cornerstone of Java's appeal and presents a strong foundation for software development. At the very least, such platform independence is an admirable goal to work towards. But under certain circumstances, commitments are necessary.

A team of Java developers might be forced to rationalize their commitment to a particular database vendor for numerous reasons, but invariably, one of the strongest motivators is performance. Leveraging a database's inherent single processes for executing stored procedures is a well-known technique to improve an application's scalability and speed. As an aside, many critics of the .Net Pet Shop application complained that the better performance achieved by that Pet Shop version was largely due to its reliance on stored procedures (our purpose isn't to argue for or against .Net or even comment on the merits of its architecture; our goal is to draw attention to the benefits of stored procedures).

In addition, a very common design pattern in Enterprise JavaBeans (EJB) development is the Fast Lane Reader, or Data Access Object (DAO) pattern. This pattern is meant to expedite read-only requests by avoiding the entity bean layer altogether and going directly to the database. In a way, the techniques described in this article extend that approach.

In this article, we examine the relationship between Java and Oracle9i. More precisely, we demonstrate some basic techniques for utilizing Oracle9i's new object-oriented features in stored procedure development. We show how the stored procedure development process can be easily and seamlessly accomplished, taking into account the complexities of modern object-oriented software development with Java.

Note: You can downloaded this article's source code from Resources.

Oracle types and inheritance

Both Oracle and Java support single inheritance, and the basics are similar for both. Oracle type inheritance, as in a Java class hierarchy, allows for ever-increasing specificity in subtypes. By expanding a type hierarchy, new columns can be added to subtypes while inheriting the basic derived features (both attributes and behavior) from the parent.

However, the syntax of how this is accomplished differs slightly between Java and Oracle's PL (Procedural Language)/SQL. In Java, object inheritance involves the keyword extends, whereas Oracle's PL/SQL uses the keyword under. PL/SQL creates object types with the create type phrase. To derive from this type, the keyword NOT FINAL must be used.

The table below compares Oracle PL/SQL and Java syntax.

Oracle PL/SQL syntax and Java syntax compared

Feature Oracle PL/SQL syntax Java syntax Type specification or definition Create type <type name> (e.g., create type Student) <access specifier> class <name> public class Student Implementation inheritance under extends Abstract types Not instantiable Abstract Subtyping Not final; Oracle types are not extendable by default Not applicable; Java objects can be extended by default Method overriding/polymorphism Overriding Subtypes override supertype methods by default; to explicitly call the supertype method, use the keyword super Self-reference SELF this Standard output DBMS_OUTPUT.PUT_LINE() System.out.println()

Traditionally, the migration from a class hierarchy in Java to a relational model required an O/R (object relational) mapping layer. Many products, such as Thought Inc.'s CocoBase Enterprise O/R, were designed to avoid manually coding this O/R layer. In addition, container-managed persistence (CMP) strives to accomplish this mapping, but, by specifying the relations in XML, does so with considerable overhead. However, when trying to employ straight Java Database Connectivity (JDBC) and SQL via the Fast Lane Reader pattern to achieve optimal performance, these approaches are not an option.

 

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