The Querydsl is a third-party library that lets us define type-safe queries. It also makes the query generation relatively easy through its fluent DSL APIs. In general, the native SQL or the Java Persistence Query Language (JPQL) does not provide any means to validate the correctness of the queries at compile time. Any query syntax or other issues are detected at run time and cause the application to fail.
In this tutorial, we’ll look into the usage of Querydsl library that lets you do the following:
- Validate that the entities used in the query exists and can be persisted in the database
- Properties used in a query exists and also can be persisted
- The SQL operators used in the query is assigned with expectant values
- Lastly, the resultant query is correct
To demonstrate the use of Querydsl, we’ll use a Spring Boot application named Pocket. This is an extremely simple application lets us bookmark our favourite URLs along with a category. Let us browse to the https://start.spring.io and create a new Spring Boot project with the web, h2, lombok, data jpa dependencies.
Following is the pom.xml file:
Notice that we have additionally included the following dependencies:
The querydsl-apt dependency is the annotation processing tool (APT) that processes the annotations in source files. This tool generates the so-called Q-types. The Q-type classes are directly relate to the entity classes of the application, but these classes are prefixed with letter Q. For…