Web design tools - Upgrading from Hibernate 2 APPENDIX D n n
Upgrading from Hibernate 2 APPENDIX D n n n Upgrading from Hibernate 2 APPENDIX D n n n Hibernate 3 represents a major change from the ways of doing things in Hibernate 2. On the whole, it is a better product, and we applaud the Hibernate developers for their efforts. One particular group of users will be made nervous by all the changes: the existing users of Hibernate 2. Well, there is good news, and there is . . . no bad news! Hibernate 3 has gone the extra mile to allow earlier users to get along. In this appendix, we will discuss the differences between the two versions and explain how a Hibernate 2 user can take advantage of them without conducting a major code rewrite. Hibernate 3 does make changes: the package names have changed, the DTDs have changed, the required libraries are different, and some of the method names and signatures have been altered. Even so, we don t think that these differences will cause you much grief when upgrading to the new version. You can run Hibernate 3 on a 1.4 or later JVM quite easily. It is possible in principle to run Hibernate 3 on a 1.3 JVM, although this will require you to recompile it from the source code and find older versions of some of the libraries that it depends upon. Once you have read this appendix, we also recommend that you consult the Hibernate 3 Migration Guide in the Documentation section of the Hibernate web site (http://hibernate. org). The Hibernate team maintains and updates this section to reflect users experiences, so you can find hints and tips gathered from developers at the cutting edge of just this sort of upgrade. Package and DTD Changes The package names for Hibernate 2 have changed with Hibernate 3. Hibernate 2 used a base package of net.sf.hibernate, while Hibernate 3 uses a base package of org.hibernate. This is, in itself, a completely trivial difference you might imagine that it is purely the result of a migration from Hibernate s hosting from SourceForge (http://sf.net or http:// sourceforge.net) to their own web site (http://hibernate.org); but, in fact, there is another reason for the change. Because of the package name change, it is possible for an application to use Hibernate 2 and Hibernate 3 simultaneously, allowing legacy Hibernate 2 code to run unmodified within the same application as more recent Hibernate 3 based components. If the same package name had been used, then it would be nearly impossible to achieve this.
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