Difference between revisions of "Creating an Object-Relational Data Type Descriptor (ELUG)"

Latest revision as of 09:44, 20 May 2009

After you create a descriptor, you must configure its various options (see Configuring a Descriptor) and use it to define mappings.

For complete information on the various types of mapping that EclipseLink supports, see Introduction to Mappings and Creating a Mapping.

For complete information on the various types of descriptor that EclipseLink supports, see Descriptor Types.

For more information, see Introduction to Object-Relational Data Type Descriptors.

Creating an Object-Relational Data Type Descriptor

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

For more information, see Object-Relational Data Type Descriptors.

How to Create an Object-Relational Data Type Descriptor Using Java

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

• setStructureName: call this method to set the name of the object-relational data type 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 EclipseLink uses if your object-relational data type data source driver uses JDBC indexed arrays.

This example shows an Employee object that is mapped to an Oracle Database using its object-relational data type features.

Employee Class

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

This example shows the object-relational data type database type (Employee_t) created to model the Employee object within the database. Such an object-relational data type 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.

Employee Object-Relational Data Type 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 EMPLOYEE_T;

This example shows how to code an object-relational data type descriptor in Java to describe the object-relational data type database type Employee_t.

Creating an Object-Relational Data Type Descriptor in Java

 import org.eclipse.persistence.mappings.structures.*;
 ...
 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 data type descriptors, see Configuring an Object-Relational Data Type Descriptor.

For more information on the object-relational data type mappings that EclipseLink supports, see Introduction to Object-Relational Data Type Mappings.

Copyright Statement