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EclipseLink/DesignDocs/MultiTenantFeatures

UNDER CONSTRUCTION

Purpose

EclipseLink provides a number of features that help with the challenges of developing multi tenant applications. This document will provide an overview of some of the ways EclipseLink can be used to support multi tenant applications.

In particular, this document will focus on applications where the application provider provides a core application and the tenant needs to extend the data provided in the application. (like Oracle Applications flex columns)

e.g. The application provider provides an Employee class that includes name and address. The tenant also wants to store the Employee Number. How can the application be architected to make storing that kind of extra data easy.

From a persistence-layer point of view, there are two areas where you must design to allow extra data.

  1. The object model and metadata
  2. The database

We will outline the options for both areas.

Object Model and Metadata

There are a number of different ways EclipseLink can support added fields in the object model.

Predefined fields

In this case, a class is designed with several generically named and typed fields. Those fields may be used by the tenant to store any data they choose. Converters could be used to control the data types coming out of the fields.

e.g. Employee contains fields called name, address, attribute1, attribute2 etc... The tenant chooses to store employee number in attribute1.

Dynamic JPA

Dynamic JPA allows the construction of a completely metadata driven application. The provider writes a dynamic JPA application that defines the set of classes and attributes that exist. The tenant calls API or provides XML that describes the additional fields on those classes.

e.g. Employee is a dynamically created entity containing name and address attributes. The tenant is allowed to construct a mapping for Employee Number by constructing an EclipseLink-orm.xml file that defines Employee with the new attribute.

Static Classes + Dynamic JPA

A static object model is provided by the provider that defines all the shared attributes. The tenant is provided with mechanism to provide extensions through Dynamic JPA. They are allowed to construct new mappings on the static classes by providing XML that describes fields that will be added to the existing object model through dynamic JPA.

e.g. Employee is a class that contains name and address attributes. The tenant is allowed to construct an eclipselink-orm.xml file that adds a virtual Employee Number field to Employee. EclipseLink's dynamic JPA functionality handles adding the field.

See https://bugs.eclipse.org/bugs/show_bug.cgi?id=331915 for the remaining work required for this configuration.

Map

Additional attributes are specified in a Map Mapping. Business logic is used to expose the fields in the Map as standard data.

e.g. Employee has attributes name and address and also a map for additional properties. To add Employee number, the tenant adds a Map Entry with key=EmployeeNumber and Value=<employees Employee Number>


Database

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