Creating UDT-to-Java mappings

The routine manager needs a mapping between SQL data values and Java™ objects to be able to pass parameters to and retrieve return results from a UDR. The SQL-to-Java data type mapping is performed according to the HCL OneDB™ JDBC Driver specification.

About this task

For built-in SQL data types, the routine manager can use mappings to existing OneDB JDBC Driver data types.

For any UDTs that your UDR uses, you must create mappings. You can use the following UDTs in UDRs written in Java code.
User-defined data type SQL statement
Distinct data type CREATE DISTINCT TYPE
Opaque data type CREATE OPAQUE TYPE
Restriction: You cannot use row or collection data types in UDRs written in Java code.

To create the mapping between a user-defined SQL data type and a Java object:

Procedure

  1. Create a user-defined class that implements the SQLData interface.
    For more information, see the OneDB JDBC Driver 2.0 specification.
  2. Bind this user-defined class to the user-defined SQL data type by using the setUDTExtName built-in procedure.
    Because the SQL statements that create UDTs do not currently provide a clause for specifying the external name of a UDT, you must define this mapping. Use the following built-in procedures with the EXECUTE PROCEDURE statement to define the mapping:
    • sqlj.setUDTExtName()

      This procedure defines the mapping between a UDT and a Java data type.

    • sqlj.unsetUDTExtName()

      This procedure removes the SQL-to-Java mapping and removes any cached copy of the Java class from database server shared memory.

      For example: 
      -- Creating or removing UDT-to-Java Mappings
EXECUTE PROCEDURE sqlj.setUDTExtName('udt_name', 
      'class_name.udtname’);
EXECUTE PROCEDURE sqlj.unsetUDTExtName('udt_name');

Results

The online examples in $ONEDB_HOME/extend/krakatoa/examples.tar include a sample implementation of a UDT written in Java code, Circle.java.