PL/SQL language can be used to develop extensions with Oracle Spatial. But PL/SQL is not a common, cross-platform development language for most programmers outside the database world. Java is a good choice for such a situation. In addition, there already exist a lot of spatial algorithms that are written in Java and licensed for use as free and open source software.
Java is very much a cross-platform technology that Oracle has invested in heavily, and it runs on all platforms on which the Oracle database runs. It can be used to develop applications that can be deployed in any architectural tier (client, middle, or data). This chapter, however, looks specifically at data-tier deployment of functionality inside the Java Virtual Machine (JVM) embedded in the Oracle database.
It is the case that many existing Oracle Spatial functions provided by the Locator and Spatial products are implemented in Java. Therefore, what is promoted in this chapter is not out of the ordinary...