ByThorben JanssenThe Java Persistence Query Language (JPQL) is the most common way to query data from a database with JPA. It enables you to reuse your mapping definitions and is easier to use than SQL. But it supports only a small subset of the SQL standard, and it also provides no support for database-specific features. So…
ByThorben JanssenSpring Data JPA provides various options to define and execute queries. All of them use JPA’s query capabilities but make them a lot easier to use. You can: reference a named native or JPQL query, derive queries from the name of a repository method and declare a query using the @Query annotation. I already explained…
ByThorben JanssenDerived queries are very comfortable to use as long as the queries are not too complicated. But as soon as you use more than 2-3 query parameters or need to define multiple joins to other entities, you need a more flexible approach. In these situations, you better use Spring Data JPA’s @Query annotation to specify…
ByThorben JanssenDTOs are easy to use and the most efficient projection for read-only operations. So, whenever you don’t need to change the requested information, you should prefer a DTO projection. But what exactly is a DTO? How does such a projection work with Hibernate? And how can you use it in your queries? I will answer…
ByThorben JanssenA lot of developers seem to have a love-hate relationship with JPA and Hibernate. They love it because it makes it easy to implement most use cases and they hate it because it also makes it easy to implement very inefficient queries. In the past, I was one of these developers myself. I liked to…