Eyal Lupu Software Blog

Hi all, As usual it took me a long time to write to my blog again but finally here it is - in this post I continue writing about JPA 2.0 (my previous post is here ), more than that this is the first entry I'm publishing in my new (the old one is here ) blog - Congratulations to me :-). Anyhow in this post I'm trying to go over some of the new functions introduced by JPA 2.0 to the JPA query language. As always my platform is Hibernate but I am using only JPA standard annotation and query syntax. The post includes the following: The INDEX function (and the @OrderColumn annotation) The TYPE expression, and The four types of case expressions My environment Hibernate 3.5.2-Final PostgreSQL 8.3

Version 2.0 of the Java Persistency API (JPA), a.k.a JSR-317 , was released a while ago (10-December-2009) and Hibernate's next version (3.5.0) will implement this version of the specification. In this, and the next, blog entries I'm planning to explorer JPA 2.0 new features and Hibernate implementation of those feature. Since this is the first post in the series I'll focus on environment setup and include only few new mapping options: The orphanRemoval option The ElementCollection annotaiotn, and The CollectionTable annotation On my next posts I'll cover some more options. My Environment Hibernate 3.5.0-CR-2 (Please notice that Hibernate 3.5 is still a candidate release so things written in this blog entry might change in the future) Database PostgreSQL 8.3

Hi all, This time about derived properties, maybe this is not a commonly used feature, and maybe even a little bit hidden one (I don't think I have ever been asked about it in any of the Hibernate courses I had lectured in and this usually a sign that people are not familiar with that feature) but once you're familiar with that it is a powerful feature - however, as always, there are considerations regarding of how and when to use it. What Is a Derived Property? A derived, or calculated, property is a read only property which its value is calculated at fetch time using SQL expressions. For example a Product class might have a price and a calculated final price which is the price including VAT. The first (not so good) solution might be something like that: @Entity @Table(name="PRODUCTS") public class Product { @Column(name="PRICE") private float price; public float getFinalPrice() { return VAT*price; } } The getFinalPrice() method...

One of my customers has just upgraded to JBoss 4.0.4-GA, the process also required us to upgrade Hibernate products to the following versions: Hibernate core – 3.2.0CR2 Hibernate Entity Manager – 3.2.0CR1 Hibernate annotations- 3.2.0CR1 We fixed some minor changes and improvements and then we bumped into the following exception javax.persistence.PersistenceException: org.hibernate.HibernateException: cannot simultaneously fetch multiple bags at org.hibernate.ejb.Ejb3Configuration.createEntityManagerFactory(Ejb3Configuration.java:217) at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:114) ........ The Exception is thrown by org.hibernate.loader.BasicLoader and it means that when loading an entity Hibernate might has to simultaneously fetch two or more bags.