Appendix 4. Kodo 4 Early Access Introduction and Errata
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## Appendix 4. Kodo 4 Early Access Introduction and Errata

Kodo 4 is a major release. Many Kodo plugin APIs have changed so that future plugins will work with both JDO 2 and JPA APIs. Additionally, the Kodo package structure and Ant tasks have changed to reflect Kodo's ability to work with multiple specifications. Finally, there have been significant changes to Kodo's object/relational mappings to enhance functionality and to make customization easier.

This release contains very little backwards compatibility for previous code that relied on Kodo APIs (as opposed to generic JDO APIs, which of course remain compatible). We will be adding legacy interfaces back in old package locations in future releases to retain backwards compatibility where possible. We are also working on migration documentation for a future release.

In the meantime, this release does support Kodo 3 mapping files and metadata extensions. See Chapter 7, Mapping for how to configure Kodo to use Kodo 3-style mapping. In general, we recommend that early adopters of this Kodo 4 release consult the documentation for individual features you want to migrate until more extensive migration information is available.

The major new features in Kodo 4 are support for both the JDO 2 and JPA specifications, and a new mapping framework that makes it trivial to create most custom mappings. The JDO Overview, JPA Overview, and Reference Guide cover these topics in detail.

## 4.1. JPA

The following JPA features are not yet supported:

- The `FlushMode` annotation is not supported, though Kodo does have configuration options and runtime APIs for configuring the flush mode.

- Reordering of SQL to meet unique constraints.

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