Registering Java Programs

Unlike PL/SQL procedures, the Java procedures are not automatically available to SQL. You have to register the Java programs through publishing the Java entry points so in which SQL could call the Java methods. Those Java methods can, in turn, create Java-to-Java calls within the JVM. For Publishing Java to SQL can be accomplished in two steps that are:

1. Create a PL/SQL program which gives a type system wrapper for the Java method. That is known as the call descriptor, which program specifies the mapping from Java types to SQL types and the mapping of the parameter modes, and many more.

2. At runtime, the PL/SQL and SQL code could call the "wrapper" program. This call is intercepted through the JVM that executes the Java method in the database's address space.

Oracle8I provides a new SQL DDL syntax which you can use to specify the PL/SQL call descriptor. A call descriptor of PL/SQL consists two categories:

• The PL/SQL procedure PSEC declaration that represents a proxy for the Java method

•  The body of the PL/SQL program that is composed of the Java method signature

The  oracle.sql  package  gives  automatic  datatype  conversion  among  Java,  PL/SQL,  and SQL.