EclipseLink/Development/DBWS/oNmMetadata

DBWS and new-format metadata

Issues Summary

At some point in the future, DBWS will switch from using 'native' EclipseLink metadata (a.k.a. Project deployment xml) to using oxm.xml and orm.xml (a.k.a JPA-style) metadata formats. In addition to using the new-format metadata, DBWS typically operates without persistent model classes; thus at runtime, a dynamic solution is required for the generation of persistent model classes.

General Solution

Similar to the current DBWS support, the new-format metadata files will be produced at design time by a DBWS utility. Later DBWS will at runtime read-in the new-format metadata files, dynamically generate persistent model classes, and realize an environment that bridges between representation in a relational database and in an XML document.

Requirements

• the new-format 'oNm.xml' metadata must support the majority of EclipseLink features (see below)
• as there are no persistent model classes on the classpath, processing the new-format metadata must use only simple scalar objects (Strings, booleans, numbers, etc.) for all capabilities and settings.
• an in-memory model of the new-format metadata can be read in from an file (or stream, URL, etc.) without persistent model classes on the classpath.
• an in-memory model of the new-format metadat can be serialized to a file (or stream, URL, etc.) without persistent model classes on the classpath.
• an in-memory model of the new-format metadata can be realized into runtime artifacts, including generating persistent model classes.
• generated persistent model classes must work when mapped simultaneously by both an OR and OX metadata model.
  i.e. an instance of a generated class must support the following: a row is retrieved from the database, built into an instance object and that very same object is serialized to XML - and vice-versa.

OR new-format metadata requirements

• Direct mappings with sufficient attribute information to support the range of datatypes used by JAX-WS web services
• session-level settings: database platform information, container settings, etc.
• session-level queries whose arguments use complex types (advanced JDBC types; PL/SQL records+collections)
  • Struct and Array mappings (211299, 221876)

OXM new-format metadata requirements

• Direct mappings with sufficient attribute information to support the range of schema types used in XML
• Composite, CompositeCollection and DirectCollection mappings
• Binary mappings to support inline or externally-attach'd binary data

Open Issues

• there are multiple solutions for dynamic generation of persistent model classes (SDO - o.e.p.sdo.helper.DynamicClassWriter; DBWS - o.e.p.internal.dynamicpersist.BaseEntityClassLoader). A separate functional spec should be created to examine the requirements and work required to refactor the multiple solutions into a common solution.

Work Required

• metadata model classes to round-trip the new-format metadata
  • JPA - partial: works for read, does not (!) work for write
  • OX - nothing exists, design work just starting now but goal is to have it for EclipseLink 2.0