Creating an Object-Relational Descriptor

You cannot create an object-relational descriptor using TopLink Workbench: you must use Java code. For more information on creating descriptors in Java code, see the Oracle TopLink API Reference.

For more information, see "Object-Relational Descriptors".

Using Java

Use the ObjectRelationalDescriptor class to define an object-relational descriptor. This class extends RelationalDescriptor to add the following methods:

• setStructureName: call this method to set the name of the object-relational structure that represents the object class in the data source.

• addFieldOrdering: call this method repeatedly to define the order in which object attributes are persisted to the data source. This defines a field index that TopLink uses if your object-relational data source driver uses JDBC indexed arrays.

Example 27-2 shows an Employee object that is mapped to an Oracle Database using its object-relational features.

Example 27-2 Employee Class

public class Employee {
    Long id;
    String firstName;
    String lastName;

    ...
}

Example 27-3 shows the object-relational database type (Employee_t) created to model the Employee object within the database. Such an object-relational database type is also known as a structure. This example also shows how to create and populate a database table (called department) that stores instances of the Employee_t audio tape.

Example 27-3 Employee Object-Relational Data Model

CREATE TYPE EMPLOYEE_T AS OBJECT(    ID NUMBER(10),    F_NAME VARCHAR2(100),    L_NAME VARCHAR2(100),) NOT FINAL;

CREATE TABLE EMPLOYEES OF TYPE EMPLOYEE_T;

Example 27-4 shows how to code an object-relational descriptor in Java to describe the object-relational database type Employee_t.

Example 27-4 Creating an Object-Relational Descriptor in Java

import oracle.toplink.objectrelational.*;

ObjectRelationalDescriptor descriptor = new ObjectRelationalDescriptor();
descriptor.setJavaClass(Employee.class);
descriptor.setTableName("EMPLOYEES");
descriptor.setStructureName("EMPLOYEE_T");
descriptor.setPrimaryKeyFieldName("ID");
descriptor.addFieldOrdering("ID");
descriptor.addFieldOrdering("F_NAME");
descriptor.addFieldOrdering("L_NAME");
descriptor.addDirectMapping("id", "OBJECT_ID");
descriptor.addDirectMapping("firstName", "F_NAME");
descriptor.addDirectMapping("lastName", "L_NAME");

For more information on configuring object-relational descriptors, see "Configuring an Object-Relational Descriptor".

For more information on the object-relational mappings that TopLink supports, see Chapter 49, "Understanding Object-Relational Mappings".