From a data access perspective, JPA supports two major types of identifiers:
The assigned identifiers must be manually set on every given entity prior to being persisted. For this reason, assigned identifiers are suitable for natural keys.
For synthetic Primary Keys, we need to use a generated entity identifier, which is supported by JPA through the use of the
There are four types of generated identifier strategies which are defined by the
AUTO identifier generator strategy chooses one of the other three strategies (
TABLE) based on the underlying relational database capabilities.
IDENTITY maps to an auto incremented column (e.g.
IDENTITY in SQL Server or
AUTO_INCREMENT in MySQL) and
SEQUENCE is used for delegating the identifier generation to a database sequence, the
TABLE generator has no direct implementation in relational databases.
This post is going to analyze why the
TABLE generator is a poor choice for every enterprise application that cares for performance and scalability.
Continue reading “Why you should never use the TABLE identifier generator with JPA and Hibernate”
As I explained in this StackOverflow question, mapping calculated properties is very easy with JPA and Hibernate.
In this post, I’m going to demonstrate how you can derive some entity property based on one or multiple persistent entity attributes.
Continue reading “How to map calculated properties with JPA and Hibernate @Formula annotation”
One year after I published the first part of the High-Performance Java Persistence, I managed to publish the print version of the book.
The book is printed on demand using Amazon CreateSpace, and it looks like as follows.
Continue reading “The print version of High-Performance Java Persistence”
Bytecode enhancement and toString
Last week, Mark Struberg, who is an Apache Software Foundation member and OpenJPA contributor, made the following statement:
Continue reading “The best way to implement equals, hashCode, and toString with JPA and Hibernate”
Flemming Harms has asked a very good question on Twitter:
Basically, we want to move the JPA XML mappings outside of the application JAR so that we can change the mapping without affecting the jar file.
Continue reading “How to use external XML mappings files (outside of JAR) with JPA and Hibernate”