EclipseLink/Development/2.1/DynamicMOXy/296967

Design Specification: MOXy support for Dynamic Persistence

ER 296967

Document History

Date	Author	Version Description & Notes
091204	Rick Barkhouse

Project overview

The goal of this feature is to enable users of EclipseLink JAXB to perform typical JAXB operations without having real .class files available for their domain objects. Users will pass in some form of metadata (EclipseLink Deployment XML or eclipselink-oxm.xml) to our JAXBContextFactory, and this metadata will be used to construct DynamicEntity objects representing the domain classes.

The ultimate purpose of this feature is to support an end-to-end JPA<->JAXB solution. EclipseLink JPA already has some support for Dynamic Persistence and this work will provide a path from Dynamic JPA to JAXB.

Goals:

• Bootstrapping of JAXB context with metadata and no class files
• Support adding arbitrary properties/mappings at run time, after initialization has been performed

Some initial groundwork was included in EclipseLink 2.0, more information is available here.

Concepts

Dynamic Persistence

The core of this feature is the Dynamic Persistence support that was initially added for JPA (found in org.eclipse.persistence.dynamic). To obtain a "dynamic" project (i.e. one that maps to classes that were generated in-memory), a "dry" project (one that does not have Java Classes specified, only class names) is passed to the DynamicTypeBuilder, passing in an instance of DynamicClassLoader, which does the work of building the in-memory classes:

InputStream metadata = ...
Project dynamicProject = DynamicTypeBuilder.loadDynamicProject(inputStream, null, new DynamicClassLoader());

When this project is used to unmarshall XML documents, the objects that are returned by EclipseLink will be subclasses of DynamicEntity. DynamicEntities offer a simple get(propertyName) / set(propertyName, propertyValue) API to manipulate their data:

DynamicEntity dynamicEmployee = jaxbContext.createUnmarshaller().unmarshal(instanceDoc);
String firstName = dynamicEmp.get("fname");
DynamicEntity dynamicAddress = dynamicEmp.get("address");
 
...
 
dynamicEmp.set("lname", "Duggar");
address.set("street", "1001 Duggar Ranch Way");

Requirements

The following sections will expand the goals of this project into more concrete requirements.

Open Issues

This section lists the open issues that are still pending that must be decided prior to fully implementing this project's requirements.

Issue #	Owner	Description / Notes

Decisions

This section lists decisions made. These are intended to document the resolution of open issues or constraints added to the project that are important.

Issue #	Description / Notes	Decision

Future Considerations

During the research for this project the following items were identified as out of scope but are captured here as potential future enhancements. If agreed upon during the review process these should be logged in the bug system.