Introduction
Inspired by this Hibernate forum post, I decided to write an article to explain how you can filter by the entity type using Criteria API.
Continue reading “How to query by entity type using JPA Criteria API”
Tag jpa
The best way to use SQL functions in JPQL or Criteria API queries with JPA and Hibernate
Introduction
When executing an entity query (e.g. JPQL, HQL or Criteria API), you can use any SQL function without having to register it as long as the function is passed directly to the WHERE clause of the underlying SQL statement.
However, if the SQL function is used in the SELECT clause, and Hibernate has not registered the SQL function (be it a database-specific or user-defined function), you will have to register the function prior to using it in an entity query.
In this article, you are going to learn various ways to register SQL functions with JPA and Hibernate.
A beginner’s guide to the Hibernate JPQL and Native Query Plan Cache
Introduction
Every JPQL query must be compiled prior to being executed, and, because this process might be resource intensive, Hibernate provides a QueryPlanCache for this purpose.
For entity queries, the query String representation is parsed into an AST (Abstract Syntax Tree). For native queries, the parsing phase cannot compile the query, so it only extracts information about the named parameters and query return type.
Continue reading “A beginner’s guide to the Hibernate JPQL and Native Query Plan Cache”
How do find and getReference EntityManager methods work when using JPA and Hibernate
Introduction
While doing my High-Performance Java Persistence training, I realized that not all developers are familiar with the getReference method of the JPA EntityManager and most of them use find almost exclusively.
In this article, we are going to see the difference between the find and getReference method so that it’s clear when to apply them depending on the underlying use case.
MariaDB 10.3 supports database sequences
Introduction
Traditionally, both MySQL and MariaDB relied on AUTO_INCREMENT columns to generate an IDENTITY Primary Key. Although IDENTITY columns are very efficient in generating the Primary Key value, when it comes to using JPA and Hibernate, the IDENTITY generator prevents us from using JDBC batch inserts.
To automatically enroll multiple INSERT, UPDATE or DELETE statements, Hibernate requires delaying the SQL statement until the Persistence Context is flushed. This works very well for the SEQUENCE identifier since the entity identifier can be fetched prior to executing the INSERT statement.
However, for IDENTITY columns, the only way to know the entity identifier is if we execute the SQL INSERT statement. And, Hibernate needs the entity identifier when persisting an entity because otherwise, it cannot build the key which is used for locating an entity in the currently running Persistence Context.