Introduction In this article, I’m going to show you how you can fetch a one-to-many relationship as a DTO projection when using JPA and Hibernate. While entities make it very easy to fetch additional relationships, when it comes to DTO projections, you need to use a ResultTransformer to achieve this goal.
Introduction In a relational database, a relationship is formed by correlating rows belonging to different tables. A table relationship is established when a child table defines a Foreign Key column that references the Primary Key column of its parent table. Every database table relationship is, therefore, built on top of Foreign Key columns, and there can be three table relationship types: one-to-many is the most common relationship, and it associates a row from a parent table to multiple rows in a child table. one-to-one requires the child table Primary Key to be… Read More
Introduction While adding a @OneToMany relationship is very easy with JPA and Hibernate, knowing the right way to map such an association so that it generates very efficient SQL statements is definitely not a trivial thing to do. In a relational database system, a one-to-many association links two tables based on a Foreign Key column so that the child table record references the Primary Key of the parent table row. As straightforward as it might be in a relational database, when it comes to JPA, the one-to-many database association can be represented… Read More
Introduction JPA translates entity state transitions to database DML statements. Because it’s common to operate on entity graphs, JPA allows us to propagate entity state changes from Parents to Child entities. This behavior is configured through the CascadeType mappings.