Introduction to Oracle Extensions

Oracle's implementation of JDBC supports versions 1.0.2 and 1.1.x of the Sun Microsystems JDK and complies with JDBC 1.22, included with these JDK versions. This chapter describes Oracle extensions to JDBC 1.22, organized into two categories:

• type extensions to comply with a subset of JDBC 2.0, which is a part of JDK 1.2

• additional Oracle-specific type extensions and performance extensions

This section describes how Oracle JDBC supports these extensions, including the Java packages created and the datatype support issues that must be considered.

Note: The JDBC OCI, Thin, and Server drivers support the same functionality, and all of the Oracle extensions.

Packages

Oracle release 8.1.5 does not support JDK 1.2. The JDBC 2.0 interfaces are part of the java.sql package that is included with the JDK 1.2. Therefore, to support JDBC 2.0 types, as well as additional Oracle extensions, the Oracle JDBC distribution includes the following Java packages:

• oracle.jdbc2 (a subset of the standard JDBC 2.0 interfaces)

• oracle.sql (classes to support all Oracle type extensions)

• oracle.jdbc.driver (classes to support database access and updates in Oracle type formats)

"Oracle JDBC Packages and Classes" further describes these packages and their classes.

Oracle Datatype Support

A key feature of the Oracle JDBC extensions is the type support in the oracle.sql.* package. This package includes classes that map to all of the Oracle SQL datatypes, acting as wrappers for raw SQL data. This functionality provides two significant advantages in manipulating SQL data:

• Accessing data directly in SQL format is more efficient than first converting it to Java format.

• Performing mathematical manipulations of the data directly in SQL format avoids the loss of precision that occurs in converting between SQL and Java formats.

Once manipulations are complete and it is time to output the information, each of the oracle.sql.* type support classes has all of the necessary methods to convert data to appropriate Java formats.

For a more detailed description of these general issues, see "Classes of the oracle.sql Package".

Specific information relating to particular oracle.sql.* datatype classes is discussed in the sections "Working with LOBs" and "Additional Type Extensions".

Oracle Object Support

Perhaps the most noteworthy Oracle8 type is Oracle objects. Oracle8 supports the use of structured objects in the database, where an object datatype is a user-defined type with nested attributes. For example, a user application could define an Employee object type, where each Employee object has a firstname attribute (a character string), a lastname attribute (another character string), and an employeenumber attribute (integer).

Oracle's JDBC implementation supports Oracle object datatypes. When you work with Oracle object datatypes in a Java application you must consider the following:

• how to map between Oracle object datatypes and Java classes

• how to store Oracle object attributes in corresponding Java objects (they can be stored in Java format or in oracle.sql.* format)

• how to convert attribute data between SQL and Java formats

• how to access data

To manually create Java classes to correspond to your Oracle objects, Oracle recommends that you use the Oracle8i JPublisher utility to create the classes. To do this, you must define attributes according to how you want to store the data. JPublisher handles this task seamlessly with command-line options.

A type map defines the correspondence between Oracle object datatypes and Java classes. Type maps are objects of a special Java class that specify which Java class corresponds to each Oracle object datatype. Oracle JDBC uses these type maps to determine which Java class to instantiate and populate when it retrieves Oracle object data from a result set.

Each Java class created to correspond to an Oracle object datatype must implement one of two supported interfaces: the JDBC-standard SQLData interface or the Oracle CustomDatum interface. Each of these interfaces specifies methods to convert data between SQL and Java. Currently, JPublisher supports only the CustomDatum interface.

JPublisher automatically defines get methods of the Java classes, which retrieve data into your Java application. For more information on the JPublisher utility, see the Oracle8i JPublisher User's Guide.

"Working with Oracle Object Types" describes Oracle JDBC support for Oracle objects.

Support for Schema Naming

Oracle JDBC classes have the ability to accept and return fully qualified schema names. A fully qualified schema name has this syntax:

{[schema_name].}[sql_type_name] 
 

where schema_name is the name of the schema and sql_type_name is the SQL type name of the object. Notice that the schema_name and the sql_type_name is separated by a dot (".").

To specify an object type in JDBC, you use its fully qualified name (that is, a schema name and SQL type name). It is not necessary to enter a schema name if the type name is in current naming space (that is, the current schema). Schema naming follows these rules:

• Both the schema name and the type name may or may not be quoted. However, if the SQL type name has a dot in it, such as CORPORATE.EMPLOYEE, the type name must be quoted.

• The JDBC driver looks for the first unquoted dot in the object's name and uses the string before the dot as the schema name and the string following the dot as the type name. If no dot is found, the JDBC driver takes the current schema as default. That is, you can specify only the type name (without indicating a schema) instead of specifying the fully qualified name if the object type name belongs to the current schema. This also explains why you must quote the type name if the type name has a dot in it.

  For example, assume that user Scott creates a type called person.address and then wants to use it in his session. Scott might want to skip the schema name and pass in person.address to the JDBC driver. In this case, if person.address is not quoted, then the dot will be detected, and the JDBC driver will mistakenly interpret person as the schema name and address as the type name.

• JDBC passes the object type name string to the database unchanged. That is, the JDBC driver will not change the character case even if it is quoted.

  For example, if ScOtT.PersonType is passed to the JDBC driver as an object type name, the JDBC driver will pass the string to the database unchanged. As another example, if there is white space between characters in the type name string, then the JDBC driver will not remove the white space.

• The JDBC driver assumes that schema names do not contain dots (".").

• The JDBC driver does not allow double quotes (") as part of the schema name or the type name.

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