TopLink uses metadata (see Section 2.9, "Working with TopLink Metadata") to describe how objects relate to a data source representation. Your mapping and configuration activities construct this metadata.
After creating the metadata, you can use it in any number of applications by referencing the metadata from a session (see Chapter 87, "Introduction to TopLink Sessions"). The TopLink runtime uses this metadata in all persistence and data transformation operations.
This chapter includes the following section:
This section describes concepts unique to TopLink mapping and configuration, including the following:
A project contains a descriptor (see Section 14.1.2, "Descriptors") for each class and each descriptor contains a mapping (see Section 14.1.3, "Mappings") for each data member that TopLink should persist or transform.
Using Oracle JDeveloper TopLink Editor or TopLink Workbench, you can export mapping and configuration metadata into a deployment XML file called
project. For more information, see Section 116.3, "Exporting Project Information".
After creating the project XML file, you must associate it with a session so that TopLink can use it at run time. For more information, see Section 89.2, "Configuring a Primary Mapping Project".
For Enterprise JavaBeans (EJB) applications where there is no session, deploy the project XML file to the target application server. In this context, the project XML file is also known as the deployment XML file.
For more information, see the following:
Descriptors describe how a Java class relates to a data source representation. They relate object classes to the data source at the data model level. For example, persistent class attributes may map to database columns.
TopLink uses descriptors to store the information that describes how an instance of a particular class can be represented in a data source (see Section 14.1.3, "Mappings"). Most descriptor information can be defined by Oracle JDeveloper TopLink Editor or TopLink Workbench, then read from the project XML file at run time.
See Chapter 16, "Introduction to Descriptors" for more information.
TopLink uses mappings to determine how to transform data between object and data source representation. Most mapping information can be defined by Oracle JDeveloper TopLink Editor or TopLink Workbench, then read from the project XML file at run time. Mappings are owned by descriptors (see Section 14.1.2, "Descriptors").
See Chapter 17, "Introduction to Mappings" for more information.