It’s hard to believe that over 3 years have gone by since the initial 1.0 release of the Java™ Persistence API. In that time we have seen it go from fledgling API to mainstream persistence standard. Along the way, many of you cut your JPA teeth using the first edition of this book, and we’re happy we were there to help! JPA 2.0 includes a host of new features, such as additional object-relational mappings, more object modeling flexibility, typed queries, and a brand-new criteria API, to name a few. With so much to talk about, we were excited to update the book and explain all the new features, but we also included some hints and tips to help you use the API in practice. If you already have experience with JPA 1.0 then you should benefit from the version tips that point out when a feature was added in 2.0. These tips were also designed to help users who are writing to a JPA 1.0 implementation, and are not yet able to make use of the 2.0 features. Those of you that are new to JPA can rest assured that you were not forgotten. We have remained true to our original intent to take someone from having no JPA knowledge all the way to being an advanced JPA’er. You should be able to quickly learn in the first two chapters what you need to know to get started. (Veteran JPA programmers might want to start at Chapter 3!) Finally, we want to thank you for making the previous edition of this book such a success. We are pleased that it has become the primary resource for JPA developers, and hope that you will find this edition equally valuable.