A beginner’s guide to Hibernate enhanced identifier generators
JPA identifier generators JPA defines the following identifier strategies: Strategy Description AUTO The persistence provider picks the most appropriate identifier strategy supported by the underlying database IDENTITY Identifiers are assigned by a database IDENTITY column SEQUENCE The persistence provider uses a database sequence for generating identifiers TABLE The persistence provider uses a separate database table to emulate a sequence object In my previous post I exampled the pros and cons of all these surrogate identifier strategies.
How do Identity, Sequence, and Table (sequence-like) generators work in JPA and Hibernate
Introduction In my previous post I talked about different database identifier strategies. This post will compare the most common surrogate primary key strategies: IDENTITY SEQUENCE TABLE (SEQUENCE) IDENTITY The IDENTITY type (included in the SQL:2003 standard) is supported by: Oracle 12c SQL Server MySQL (AUTO_INCREMENT) HSQLDB The IDENTITY generator allows an integer/bigint column to be auto-incremented on demand. The increment process happens outside of the current running transaction, so a roll-back may end-up discarding already assigned values (value gaps may happen). The increment process is very efficient since it uses a database… Read More
Hibernate and UUID identifiers
Introduction In this article, we are going to see how the UUID entity attributes are persisted when using JPA and Hibernate, for both assigned and auto-generated identifiers. In my previous post I talked about UUID surrogate keys and the use cases when there are more appropriate than the more common auto-incrementing identifiers. A UUID database type There are several ways to represent a 128-bit UUID, and whenever in doubt I like to resort to Stack Exchange for an expert advice. Because table identifiers are usually indexed, the more compact the database type… Read More
The hi/lo algorithm
Introduction In my previous post I talked about various database identifier strategies, you need to be aware of when designing the database model. We concluded that database sequences are very convenient because they are both flexible and efficient for most use cases. But even with cached sequences, the application requires a database round-trip for every new the sequence value. If your applications demand a high number of insert operations per transaction, the sequence allocation may be optimized with a hi/lo algorithm. The hi/lo algorithm The hi/lo algorithms split the sequences domain into… Read More
A beginner’s guide to natural and surrogate database keys
Types of primary keys All database tables must have one primary key column. The primary key uniquely identifies a row within a table therefore it’s bound by the following constraints: UNIQUE NOT NULL IMMUTABLE When choosing a primary key we must take into consideration the following aspects: the primary key may be used for joining other tables through a foreign key relationship the primary key usually has an associated default index, so the more compact the data type the less space the index will take the primary key assignment must ensure uniqueness… Read More
The minimal configuration for testing Hibernate
Introduction In my previous post I announced my intention of creating a personal Hibernate course. The first thing to start with is a minimal testing configuration. You only need Hibernate In a real production environment you won’t use Hibernate alone, as you may integrate it in a Java EE or Spring container. For testing Hibernate features you don’t need a full-blown framework stack, you can simply rely on Hibernate flexible configuration options.
The anatomy of Connection Pooling
Introduction All projects I’ve been working on have used database connection pooling and that’s for very good reasons. Sometimes we might forget why we are employing one design pattern or a particular technology, so it’s worth stepping back and reason on it. Every technology or technological decision has both upsides and downsides, and if you can’t see any drawback you need to wonder what you are missing. The database connection life-cycle Every database read or write operation requires a connection. So let’s see how database connection flow looks like: The flow goes… Read More
Maven and Java multi-version modules
Introduction In this article, you are going to learn how to configure Maven to choose a specific Java version when the OS has multiple Java versions installed. For instance, FlexyPool uses Java 8 for all modules, except for the flexy-pool-core-java9 module that needs to be built using Java 9.
Caching best practices
Introduction There is an irresistible attraction to writing custom caching solutions since it seems to be the easiest path to “improving” the overall application performance. Well, caching is a great technique, but there are few steps to consider before even considering it.
