Database Platforms

OracleAS TopLink communicates with databases using Structured Query Language (SQL). Because each database platform uses its own variation on the basic SQL language, OracleAS TopLink must adjust the SQL it uses to communicate with the database to ensure that the application runs smoothly.

This section describes OracleAS TopLink support for:

JDBC-SQL and Native SQL
Custom Platforms

JDBC-SQL and Native SQL

By default, OracleAS TopLink accesses the database using JDBC-SQL and automatically performs the conversions between Java types and database types. OracleAS TopLink provides the conversions listed in Table 5-1 automatically.

Table 5-1 JDBC-SQL Conversion Types

Class	Oracle Type	DB2 Type	dBase Type	Sybase Type	Microsoft Access Type
`java.lang.Boolean`	NUMBER	SMALLINT	NUMBER	BIT default 0	SHORT
`java.lang.Byte`	NUMBER	SMALLINT	NUMBER	SMALLINT	SHORT
`java.lang.Byte[]`	LONG RAW	BLOB	BINARY	IMAGE	LONGBINARY
`java.lang.Integer`	NUMBER	INTEGER	NUMBER	INTEGER	LONG
`java.lang.Long`	NUMBER	INTEGER	NUMBER	NUMERIC	DOUBLE
`java.lang.Float`	NUMBER	FLOAT	NUMBER	FLOAT(16)	DOUBLE
`java.lang.Double`	NUMBER	FLOAT	NUMBER	FLOAT(32)	DOUBLE
`java.lang.Short`	NUMBER	SMALLINT	NUMBER	SMALLINT	SHORT
`java.lang.String`	VARCHAR2	VARCHAR	CHAR	VARCHAR	TEXT
`java.lang.Character`	CHAR	CHAR	CHAR	CHAR	TEXT
`java.lang.Character[]`	LONG	CLOB	MEMO	TEXT	LONGTEXT
`java.math.BigDecimal`	NUMBER	DECIMAL	NUMBER	NUMERIC	DOUBLE
`java.math.BigInteger`	NUMBER	DECIMAL	NUMBER	NUMERIC	DOUBLE
`java.sql.Date`	DATE	DATE	DATE	DATETIME	DATETIME
`java.sql.Time`	DATE	TIME	CHAR	DATETIME	DATETIME
`java.sql.Timestamp`	DATE	TIMESTAMP	CHAR	DATETIME	DATETIME

OracleAS TopLink provides the required customization by enabling you to specify your database platform. OracleAS TopLink provides specific support for the following platforms:

Oracle databases
IBM DB2
IBM DBase
IBM Cloudscape
IBM Informix
Microsoft Access
Microsoft SQL Server
Sybase SQL Server
JDBC
PointBase databases

Specify your database platform in the login element of the sessions.xml file or the login section of your Java project configuration file (project.java). If you set your database platform in OracleAS TopLink Mapping Workbench, then OracleAS TopLink Mapping Workbench and the OracleAS TopLink Sessions Editor manage the database platform configuration for you automatically.

Example 5-1 Specifying an Oracle Database Platform in the sessions.xml File

For clarity, the code that sets the platform class is bold in this example.

<session>
  ...
  <login>
    ...
    <platform-class>
        oracle.toplink.internal.databaseaccess.OraclePlatform
    </platform-class>
    ...
  </login>
...
</session>

Example 5-2 Specifying an Oracle Database Platform in Java

project.getLogin().useOracle();

Custom Platforms

You can specify a custom database platform for your OracleAS TopLink application. Custom platform support enables you to use a database when OracleAS TopLink has no predefined platform.

To enable custom database platform support, create a new platform class that extends one of the existing platform classes, and call the class at runtime by referencing it in the session configuration file (the sessions.xml file), as Example 5-1 illustrates.