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… Read More

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.

EAGER fetching is a code smell when using JPA and Hibernate

Introduction Hibernate fetching strategies can really make a difference between an application that barely crawls and a highly responsive one. In this post, I’ll explain why you should prefer query-based fetching instead of global fetch plans. Fetching 101 Hibernate defines four association retrieving strategies: Fetching Strategy Description Join The association is OUTER JOINED in the original SELECT statement Select An additional SELECT statement is used to retrieve the associated entity(entities) Subselect An additional SELECT statement is used to retrieve the whole associated collection. This mode is meant for to-many associations Batch An… Read More