How-to articles, tricks, and solutions about JPA

In the Java Persistence API (JPA), the FetchType enum is used to specify the strategy for fetching data from the database.

If you are using Hibernate and you see the error "MultipleBagFetchException: cannot simultaneously fetch multiple bags", it means that you are trying to fetch multiple collections of an entity using a single Hibernate query.

To update an entity using Spring Data JPA, you will need to follow these steps:

In a JPA entity mapping, the @JoinColumn annotation is used to specify the foreign key column for a many-to-one or one-to-one relationship.

If you are seeing the error "No Persistence provider for EntityManager named [persistence-unit-name]" in your Java application, it means that the persistence provider (e.g.

To set default values for columns in JPA (Java Persistence API), you can use the @Column annotation and the columnDefinition attribute.

If you are seeing the error "Cannot determine embedded database driver class for database type NONE" in a Spring Boot application, it means that the application is trying to auto-configure an embedded database, but it is unable to determine which database

This exception is usually thrown when you are trying to access a property that does not exist in the entity class you are querying.

To select specific columns using Spring JPA, you can use the @Query annotation and specify the columns in the SELECT clause of the JPQL query.

In a JPA entity relationship, the CascadeType.ALL annotation specifies that all operations (persist, merge, remove, refresh, and detach) that are performed on the parent entity should be cascaded to the child entity.

Java Persistence API (JPA) is a specification for object-relational mapping (ORM) in Java.