Chapter 1. Introduction

Hibernate, like all other object/relational mapping tools, requires metadata that governs the transformation of data from one representation to the other. In Hibernate 2.x mapping metadata is most of the time declared in XML text files. Alternatively XDoclet can be used utilizing Javadoc source code annotations together with a compile time preprocessor.

The same kind of annotation support is now available in the standard JDK, although more powerful and with better tools support. IntelliJ IDEA and Eclipse for example, support auto-completion and syntax highlighting of JDK 5.0 annotations which are compiled into the bytecode and read at runtime using reflection. No external XML files are needed.

The JPA specification recognizes the interest and the success of the transparent object/relational mapping paradigm. It standardizes the basic APIs and the metadata needed for any object/relational persistence mechanism. Hibernate EntityManager implements the programming interfaces and lifecycle rules as defined by the JPA persistence specification and together with Hibernate Annotations offers a complete (and standalone) JPA persistence solution on top of the mature Hibernate core. You may use a combination of all three together, annotations without JPA programming interfaces and lifecycle, or even pure native Hibernate, depending on the business and technical needs of your project. At all times you cann fall back to Hibernate native APIs, or if required, even to native JDBC and SQL.